Home » CEEFAX disks » telesoftware3.adl » 23_10_87/T\SWR01
23_10_87/T\SWR01
This website contains an archive of files for the Acorn Electron, BBC Micro, Acorn Archimedes, Commodore 16 and Commodore 64 computers, which Dominic Ford has rescued from his private collection of floppy disks and cassettes.
Some of these files were originally commercial releases in the 1980s and 1990s, but they are now widely available online. I assume that copyright over them is no longer being asserted. If you own the copyright and would like files to be removed, please contact me.
| Tape/disk: | Home » CEEFAX disks » telesoftware3.adl |
| Filename: | 23_10_87/T\SWR01 |
| Read OK: | ✔ |
| File size: | 4789 bytes |
| Load address: | 0000 |
| Exec address: | 0000 |
Duplicates
There is 1 duplicate copy of this file in the archive:
- CEEFAX disks » telesoftware3.adl » 23_10_87/T\SWR01
- CEEFAX disks » telesoftware8.adl » 02-07-88/T\SWR01
File contents
Mastering Sideways ROM & RAM - Module 01 - Introduction
-------------------------------------------------------
It is possible to write sideways ram software on a BBC B or B+ 64k
without sideways ram but, if you use one of these machines, it will
save you a great deal of time blowing and erasing eproms if SWR is
available to test the software as it is being developed.
Adding SWR to the BBC B+ 64k is very straightforward as Acorn
produce a 64k SWR upgrade which can be fitted by Acorn dealers. Don't
attempt to fit it yourself unless you are absolutely sure you have the
skill needed to complete the job.
Fitting an SWR upgrade to the BBC B is a job most users can attempt
without incuring a dealer's service charge. There are many sideways
ram and rom boards available which can be fitted without soldering any
components. You should look carefully at the facilities offered by the
various manufacturers of SWR boards and choose the board that best
suits your needs. I recommend that you consider the following points
when you look for a SWR board.
1. A mimimum of 16k of sideways ram is required. 32k or 64k is useful
but not essential. Most boards which use static rams do so because the
design is much simpler. There is an old designer's joke that the
difference between static and dynamic ram is that static ram works.
Don't let this nonsense prevent you buying a dynamic ram board.
2. Physical switching for read and write protection of the SWR is
highly desirable. Read protection will be used to switch out the
offending memory when you load an invalid rom image which causes the
computer to hang up. Write protection is useful if you want to develop
rom images that are protected against running in SWR. Software
switching of read and write protection is a poor substitute for real
switches that click.
3. Look carefully at the way in which flying leads are attached to
the main computer circuit board. Compare the different methods
manufacturers use. Some boards use quite unprofessional design
techniques.
4. Battery backup of SWR is useful, but not essential.
5. Many SWR boards have sockets for extra roms. The BBC B MOS will
support up to sixteen sideways rom or ram banks. The main circuit
board has only four sideways rom sockets, two of which are taken up
with BASIC and the DFS. The extra sockets on a sideways ram/rom board
will be useful if you have more roms than rom sockets.
There are a number of manufacturers who produce boards which meet
these requirements to a greater or lesser extent. Which manufacturer
you choose is up to you. You can be sure that all the boards produced
by reputable companies will perform adequately but it is not possible
to recommend one board as better in every respect than any other.
When you have fitted the upgrade board into your computer you might
want to store the programs contained in your roms on disc or tape and
then load and run the rom images in SWR. All Acorn supported languages
will run in unprotected SWR and most rom images will run in write
protected SWR.
Where the copyright of the software contained in a rom is not owned
by Acorn, specific permission must be obtained from the owner of the
copyright before copying it onto disc or tape.
In Acorn's User Guide (Part no. 408000, Issue no. 2, March 1984,
page 20) it states "... you can keep a library of paged roms on disc,
which can be called up in the same way as roms installed inside the
BBC Microcomputer. However, in using this facility you must ensure
that you do not infringe the rights of the owner of the copyright of
the program contained in the rom".
As long as you do not infringe the rights of the owner of the
copyright of the program, roms can be saved onto a library disc and
run in ram. Some software producers take a less enlightened view than
Acorn take to running their roms in SWR and attempt to protect them
against it. Most of this protection does little to deter professional
software pirates but it should be taken as an indicator of the
copyright owner's unwillingness to allow his or her work to be used in
SWR.
If you want to ensure that your own work will only run in eproms and
not in SWR there are a number of techniques you can try. An 8k rom
image is duplicated from &A000 and one of the methods of protecting 8k
rom images is to add &2000 to the subroutine and jump addresses.
Another, far less common, method is to prevent the rom image running
in socket &0F. This socket is commonly used for SWR on rom boards and
the only way to get these rom images to run in socket &0F is to
disassemble and modify them. When you have completed this course you
will certainly know what to look for in a rom disassembly if you
wanted to do this but it is quite a good way of detering most amateur
rom pilferers.
I will now begin to explore the programming techniques needed to use
SWR. There are a number of MOS subroutines, memory locations and
registers associated with SWR. Rather than examine them all now I will
consider the calls and locations as they arise throughout the course.
In this module I will look at the paged rom select register at &FE30,
the paged memory select register at &FE34, the MOS subroutine Osrdrm,
and Osbytes &72 and &AA.
There are differences in the way in which the paged rom select
register and the paged memory select register are used in the BBC B,
the BBC B+ and the Master computers. The reason for the differences
can be seen by examining the memory maps of these machines (figures
1.1, 1.2 and 1.3).
&FFFF +-------+ &FFFF
! !
! MOS !
! !
&BFFF --+-------+-------+-------+-------+ &C000
! ROM &C! ROM &D! ROM &E! ROM &F!
! ! ! ! !
! ! ! DFS ! BASIC !
&8000 --+-------+-------+-------+-------+ &7FFF
Up to 16 sideways rom/ram banks ! !
! User !
! memory!
! !
! !
&1900 +-------+ Oshwm
! !
&0000 +-------+ &0000
Figure 1.1 Memory map of the BBC B
----------------------------------
The BBC B MOS supports up to sixteen paged roms although an
expansion board is required if more than four roms are to be used. The
paged rom select register at &FE30 is a 4 bit write only register
which determines which of the 16 roms is switched into the main memory
map. If you want to read the contents of this register you should read
the zero page copy of it at &F4. The most significant nybble of the
paged rom select register is not used on the BBC B.
&FFFF +-------+ &FFFF
! !
! MOS !
! !
&BFFF --+-------+-------+-------+-------+ &C000
! ROM &C! ROM &D! ROM &E! ROM &F+-------+ &AFFF
! ! ! ! ! Paged !
! ! ! DFS ! BASIC ! memory!
&8000 --+-------+-------+-------+-------+-------+ &8000
Up to 16 sideways rom/ram banks ! ! !
! User ! Shadow!
! memory! ram !
! ! !
! +-------+ &3000
&1900 +-------+ Oshwm
! !
&0000 +-------+ &0000
Figure 1.2 Memory map of the BBC B+
-----------------------------------
The BBC B+ has a similar memory map to the BBC B but in addition to
the paged roms it also supports paged or shadow memory. The paged
memory (shadow ram) select register at &FE34 is used to determine
whether or not the shadow ram is used as screen memory. This register
should only be altered using Osbyte &72 (*FX114) or the command
*SHADOW. The BBC B+ has a "spare" 12k of paged memory from &8000 to
&AFFF. This can be switched in or out of the main memory map using the
most significant bit of the paged rom select register at &FE30.
Setting the most significant bit of the paged rom select register has
no effect on the BBC B but on the BBC B+ it switches the paged memory
from &8000 to &AFFF into the main memory map. BBC Telesoftware has
broadcast a program that uses this technique to allow BBC B+ 64k
computer users to load and run 8k service roms in this area of paged
memory.
The Master computer uses a slightly different memory map to the B
series. The "spare" 12k of paged memory has now been split into two
areas, one from &8000 to &8FFF and the other from &C000 to &DFFF. The
paged ram from &8000 to &8FFF is used by the MOS as a soft key buffer,
character font, and VDU workspace. The paged ram from &C000 to &DCFF
is available as paged rom workspace and the paged ram from &DD00 to
&DFFF is used as MOS workspace.
&FFFF +-------+ &FFFF
! !
! MOS +-------+ &DFFF
! !Wkspace!
&BFFF --+-------+-------+-------+-------+-------+ &C000
! ROM &C! ROM &D! ROM &E! ROM &F!
! ! ! ! !
! BASIC ! ADFS ! View ! Term. +-------+ &8FFF
&8000 --+-------+-------+-------+-------+-------+ &8000
Up to 16 Sideways rom/ram banks ! ! !
! User ! Shadow!
! memory! ram !
! ! !
! +-------+ &3000
! !
&0E00 +-------+ Oshwm
&0000 +-------+ &0000
Figure 1.3 Memory map of the BBC Master
---------------------------------------
Paged rom workspace on the BBC B and B+ is just below the user
memory. The BBC B DFS claims 2.75k of workspace from &0E00 to &1900.
This workspace can be in paged memory on the Master series allowing
Oshwm to stay at &0E00 with all filing systems. Bit 3 of the paged
memory select register at &FE34 is used to overlay the paged rom
workspace onto the Master MOS so that it appears above the paged rom
using it. Bit 3 of the paged memory select register can be toggled
directly but you must not directly alter any other bit in this
register. This topic will be covered in more detail in modules 11 and
12 which deal with paged rom workspace.
The use of the least significant nybble of the paged rom select
register at is common to all BBC micros. The operating system uses
this register, and the zero page copy of it at &F4, to keep track of
which paged rom is being used at any time. If you want to alter this
register directly you can only do so from machine code. If you alter
it from BASIC or any other language rom you will cause the computer to
hang up.
The order in which the paged rom select register and its copy at &F4
are altered is important. You must store the same number in both
locations and alter &F4 first. Immediatly after altering &F4 you must
store the same value in &FE30. For example:
LDA #&0A
STA &F4
STA &FE30
This code will switch bank &0A into the main memory map. If you
reverse the order of the last two instructions you will find that 99%
of the time everything works properly but, sooner or later, an
interupt occuring between the two store instructions will cause to
computer to hang up. Switching a paged rom into the main memory map in
this way can be quite useful if you want to transfer the contents of a
rom into user memory or transfer the contents of user memory into a
particular sideways ram.
There is an official way to read a byte of memory from any paged
rom. This uses the operating system call Osrdrm at &FFB9 with the
relevant paged rom number in the Y register and the address of the
byte in the paged rom in locations &F6 and &F7 (the paged rom
pointers). The value of the byte read by Osrdrm is returned in the
accumulator. The X, Y and status registers will be undefined after the
call.
Both these techniques are demonstrated in the program READROM. When
the program is running it uses Osrdrm to read the title string in
every rom socket that has an active rom image and then prompts the
user to choose which rom number, from 0-15, to switch into the main
memory map. The chosen rom is switched in and copied from &8000 to
&3C00 and then switched back out again. The rom image can then be
examined and, if required, saved to the currently active filing
system. Although some of the program is in BASIC the switching and
copying can only be done in machine code.
The program uses Osbyte &AA to find the start of the rom information
table. This call returns the origin of a 16 byte table containing one
byte per paged rom. Each byte contains the rom type byte contained in
location &8006 of the rom or contains zero if an active rom is not
present. Rom type bytes are an important part of the rom header and
will be dealt with in more detail when rom headers are considered in
module 2.
Chain the program READROM and satisfy yourself that it works
properly. It must run in the I/O processor and will not work in a
second processor.
There are two machine code routines used in the program. The first
(lines 200-430) is called once for each possible rom number from 0 to
15. It looks up the address of the start of the rom information table
with Osbyte &AA (lines 210-240) and then uses the number of the rom as
an offset in the Y register to see if there is a valid rom in the
socket being considered (line 280). If there is a valid rom image
present the routine reads the title of the rom using Osrdrm and
displays it on the screen (lines 340-430). The rom title always starts
at &8009 in a valid rom image and always ends with a binary zero.
The second machine code routine is in lines 440-700. This stores the
current rom number (lines 450-460) before switching the chosen rom
into the main memory map (lines 470-490). It then copies the chosen
rom image into user memory (lines 500-660), and finally switches the
original rom back into the main memory map (lines 670-690).
The BASIC part of the program is mainly concerned with displaying
the copy of the rom image on the screen (lines 860-990) and, if
required, with saving a copy of the rom image onto disc or tape
(PROCsave, lines 1000-1190). Before it makes a copy of the rom image
onto disc the program compares the first &100 bytes of the image with
&100 bytes 8k higher in memory (lines 1090-1110). If every pair of
&100 bytes is identical the rom is recognised as an 8k image and only
the first &2000 bytes are saved.
The program READROM, as well as illustrating the techniques
described above, will be useful in later modules when you will want to
examine or save the contents of sideways ram banks. The program can be
modified to produce another program to load rom images into any
sideways ram bank, including the paged memory bank of the BBC B+. This
has been left as an exercise for you to complete.
10 REM: READROM
20 MODE7
30 HIMEM=&3C00
40 DIM mcode &100
50 select=&FE30
60 osrdrm=&FFB9
70 osasci=&FFE3
80 osbyte=&FFF4
90 oscli=&FFF7
100 copy=&70
110 temp=&71
120 read=&72
130 write=&74
140 romnumber=&F4
150 rompoint=&F6
160 ON ERROR PRINT : END
170 FOR pass=0 TO 2 STEP 2
180 P%=mcode
190 [ OPT pass
200 .number
210 LDA #&AA
220 LDX #0
230 LDY #&FF
240 JSR osbyte \ Find rom table
250 STX read
260 STY read+1
270 LDY copy
280 LDA (read),Y
290 BEQ finish
300 LDA #8
310 STA rompoint
320 LDA #&80
330 STA rompoint+1
340 .readname
350 INC rompoint
360 LDY copy
370 JSR osrdrm
380 CMP #ASC(" ")
390 BCC finish
400 JSR osasci
410 JMP readname
420 .finish
430 RTS
440 .move
450 LDA romnumber
460 STA temp
470 LDA copy
480 STA romnumber
490 STA select
500 LDA #&80
510 STA read+1
520 LDA #&3C
530 STA write+1
540 LDY #0
550 STY read
560 STY write
570 .relocate
580 LDA (read),Y
590 STA (write),Y
600 INY
610 BNE relocate
620 INC read+1
630 INC write+1
640 LDA read+1
650 CMP #&C0
660 BNE relocate
670 LDA temp
680 STA romnumber
690 STA select
700 RTS
710 ]
720 NEXT
730 FOR socket=0 TO 15
740 ?copy=socket
750 IF socket<10 PRINT;" ";
760 PRINT;socket;" ";
770 CALL number
780 PRINT
790 NEXT
800 VDU14
810 REPEAT
820 INPUT'"Which ROM &(0-15) "socket
830 UNTIL socket >= 0 AND socket < 16
840 ?copy=socket
850 CALL move
860 PRINT'"<SHIFT> to scroll, <ESCAPE> to exit"
870 ON ERROR PROCsave
880 FOR block=&3C00 TO &7BFF STEP 8
890 PRINT';~block+&4400;" ";
900 FOR memory=0 TO 7
910 byte=block?memory
920 IF byte<16 VDU48
930 PRINT;~byte;" ";
940 NEXT
950 FOR memory=0 TO 7
960 byte=memory?block
970 IF byte>31 AND byte<127 VDUbyte ELSE VDU46
980 NEXT
990 NEXT
1000 PROCsave
1010 END
1020 DEFPROCsave
1030 ON ERROR PRINT : END
1040 VDU15
1050 INPUT''"Save ROM? (Y/N) "yes$
1060 REPEAT
1070 IF yes$="Y" INPUT"Filename? : "filename$ ELSE INPUT"An
other? (Y/N) "yes$ : IF yes$<>"Y" END ELSE RUN
1080 size=FALSE
1090 FOR block=&3C00 TO &3D00
1100 IF ?block <> ?(block+&2000) size= TRUE
1110 NEXT
1120 IF size=TRUE size=&4000 ELSE size=&2000
1130 $mcode="SAVE "+filename$+" 3C00+"+STR$~(size)+" FFFF80
00 FFFF8000"
1140 X%=mcode MOD 256
1150 Y%=mcode DIV 256
1160 CALL oscli
1170 yes$=""
1180 UNTIL FALSE
1190 ENDPROC
00000000 4d 61 73 74 65 72 69 6e 67 20 53 69 64 65 77 61 |Mastering Sidewa|
00000010 79 73 20 52 4f 4d 20 26 20 52 41 4d 20 2d 20 4d |ys ROM & RAM - M|
00000020 6f 64 75 6c 65 20 30 31 20 2d 20 49 6e 74 72 6f |odule 01 - Intro|
00000030 64 75 63 74 69 6f 6e 0d 2d 2d 2d 2d 2d 2d 2d 2d |duction.--------|
00000040 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d |----------------|
*
00000060 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 0d |---------------.|
00000070 0d 20 20 49 74 20 69 73 20 70 6f 73 73 69 62 6c |. It is possibl|
00000080 65 20 74 6f 20 77 72 69 74 65 20 73 69 64 65 77 |e to write sidew|
00000090 61 79 73 20 72 61 6d 20 73 6f 66 74 77 61 72 65 |ays ram software|
000000a0 20 6f 6e 20 61 20 42 42 43 20 42 20 6f 72 20 42 | on a BBC B or B|
000000b0 2b 20 36 34 6b 0d 77 69 74 68 6f 75 74 20 73 69 |+ 64k.without si|
000000c0 64 65 77 61 79 73 20 72 61 6d 20 62 75 74 2c 20 |deways ram but, |
000000d0 69 66 20 79 6f 75 20 75 73 65 20 6f 6e 65 20 6f |if you use one o|
000000e0 66 20 74 68 65 73 65 20 6d 61 63 68 69 6e 65 73 |f these machines|
000000f0 2c 20 69 74 20 77 69 6c 6c 0d 73 61 76 65 20 79 |, it will.save y|
00000100 6f 75 20 61 20 67 72 65 61 74 20 64 65 61 6c 20 |ou a great deal |
00000110 6f 66 20 74 69 6d 65 20 62 6c 6f 77 69 6e 67 20 |of time blowing |
00000120 61 6e 64 20 65 72 61 73 69 6e 67 20 65 70 72 6f |and erasing epro|
00000130 6d 73 20 69 66 20 53 57 52 20 69 73 0d 61 76 61 |ms if SWR is.ava|
00000140 69 6c 61 62 6c 65 20 74 6f 20 74 65 73 74 20 74 |ilable to test t|
00000150 68 65 20 73 6f 66 74 77 61 72 65 20 61 73 20 69 |he software as i|
00000160 74 20 69 73 20 62 65 69 6e 67 20 64 65 76 65 6c |t is being devel|
00000170 6f 70 65 64 2e 0d 0d 20 20 41 64 64 69 6e 67 20 |oped... Adding |
00000180 53 57 52 20 74 6f 20 74 68 65 20 42 42 43 20 42 |SWR to the BBC B|
00000190 2b 20 36 34 6b 20 69 73 20 76 65 72 79 20 73 74 |+ 64k is very st|
000001a0 72 61 69 67 68 74 66 6f 72 77 61 72 64 20 61 73 |raightforward as|
000001b0 20 41 63 6f 72 6e 0d 70 72 6f 64 75 63 65 20 61 | Acorn.produce a|
000001c0 20 36 34 6b 20 53 57 52 20 75 70 67 72 61 64 65 | 64k SWR upgrade|
000001d0 20 77 68 69 63 68 20 63 61 6e 20 62 65 20 66 69 | which can be fi|
000001e0 74 74 65 64 20 62 79 20 41 63 6f 72 6e 20 64 65 |tted by Acorn de|
000001f0 61 6c 65 72 73 2e 20 44 6f 6e 27 74 0d 61 74 74 |alers. Don't.att|
00000200 65 6d 70 74 20 74 6f 20 66 69 74 20 69 74 20 79 |empt to fit it y|
00000210 6f 75 72 73 65 6c 66 20 75 6e 6c 65 73 73 20 79 |ourself unless y|
00000220 6f 75 20 61 72 65 20 61 62 73 6f 6c 75 74 65 6c |ou are absolutel|
00000230 79 20 73 75 72 65 20 79 6f 75 20 68 61 76 65 20 |y sure you have |
00000240 74 68 65 0d 73 6b 69 6c 6c 20 6e 65 65 64 65 64 |the.skill needed|
00000250 20 74 6f 20 63 6f 6d 70 6c 65 74 65 20 74 68 65 | to complete the|
00000260 20 6a 6f 62 2e 0d 0d 20 20 46 69 74 74 69 6e 67 | job... Fitting|
00000270 20 61 6e 20 53 57 52 20 75 70 67 72 61 64 65 20 | an SWR upgrade |
00000280 74 6f 20 74 68 65 20 42 42 43 20 42 20 69 73 20 |to the BBC B is |
00000290 61 20 6a 6f 62 20 6d 6f 73 74 20 75 73 65 72 73 |a job most users|
000002a0 20 63 61 6e 20 61 74 74 65 6d 70 74 0d 77 69 74 | can attempt.wit|
000002b0 68 6f 75 74 20 69 6e 63 75 72 69 6e 67 20 61 20 |hout incuring a |
000002c0 64 65 61 6c 65 72 27 73 20 73 65 72 76 69 63 65 |dealer's service|
000002d0 20 63 68 61 72 67 65 2e 20 54 68 65 72 65 20 61 | charge. There a|
000002e0 72 65 20 6d 61 6e 79 20 73 69 64 65 77 61 79 73 |re many sideways|
000002f0 0d 72 61 6d 20 61 6e 64 20 72 6f 6d 20 62 6f 61 |.ram and rom boa|
00000300 72 64 73 20 61 76 61 69 6c 61 62 6c 65 20 77 68 |rds available wh|
00000310 69 63 68 20 63 61 6e 20 62 65 20 66 69 74 74 65 |ich can be fitte|
00000320 64 20 77 69 74 68 6f 75 74 20 73 6f 6c 64 65 72 |d without solder|
00000330 69 6e 67 20 61 6e 79 0d 63 6f 6d 70 6f 6e 65 6e |ing any.componen|
00000340 74 73 2e 20 59 6f 75 20 73 68 6f 75 6c 64 20 6c |ts. You should l|
00000350 6f 6f 6b 20 63 61 72 65 66 75 6c 6c 79 20 61 74 |ook carefully at|
00000360 20 74 68 65 20 66 61 63 69 6c 69 74 69 65 73 20 | the facilities |
00000370 6f 66 66 65 72 65 64 20 62 79 20 74 68 65 0d 76 |offered by the.v|
00000380 61 72 69 6f 75 73 20 6d 61 6e 75 66 61 63 74 75 |arious manufactu|
00000390 72 65 72 73 20 6f 66 20 53 57 52 20 62 6f 61 72 |rers of SWR boar|
000003a0 64 73 20 61 6e 64 20 63 68 6f 6f 73 65 20 74 68 |ds and choose th|
000003b0 65 20 62 6f 61 72 64 20 74 68 61 74 20 62 65 73 |e board that bes|
000003c0 74 0d 73 75 69 74 73 20 79 6f 75 72 20 6e 65 65 |t.suits your nee|
000003d0 64 73 2e 20 49 20 72 65 63 6f 6d 6d 65 6e 64 20 |ds. I recommend |
000003e0 74 68 61 74 20 79 6f 75 20 63 6f 6e 73 69 64 65 |that you conside|
000003f0 72 20 74 68 65 20 66 6f 6c 6c 6f 77 69 6e 67 20 |r the following |
00000400 70 6f 69 6e 74 73 0d 77 68 65 6e 20 79 6f 75 20 |points.when you |
00000410 6c 6f 6f 6b 20 66 6f 72 20 61 20 53 57 52 20 62 |look for a SWR b|
00000420 6f 61 72 64 2e 0d 0d 31 2e 20 20 41 20 6d 69 6d |oard...1. A mim|
00000430 69 6d 75 6d 20 6f 66 20 31 36 6b 20 6f 66 20 73 |imum of 16k of s|
00000440 69 64 65 77 61 79 73 20 72 61 6d 20 69 73 20 72 |ideways ram is r|
00000450 65 71 75 69 72 65 64 2e 20 33 32 6b 20 6f 72 20 |equired. 32k or |
00000460 36 34 6b 20 69 73 20 75 73 65 66 75 6c 0d 62 75 |64k is useful.bu|
00000470 74 20 6e 6f 74 20 65 73 73 65 6e 74 69 61 6c 2e |t not essential.|
00000480 20 4d 6f 73 74 20 62 6f 61 72 64 73 20 77 68 69 | Most boards whi|
00000490 63 68 20 75 73 65 20 73 74 61 74 69 63 20 72 61 |ch use static ra|
000004a0 6d 73 20 64 6f 20 73 6f 20 62 65 63 61 75 73 65 |ms do so because|
000004b0 20 74 68 65 0d 64 65 73 69 67 6e 20 69 73 20 6d | the.design is m|
000004c0 75 63 68 20 73 69 6d 70 6c 65 72 2e 20 54 68 65 |uch simpler. The|
000004d0 72 65 20 69 73 20 61 6e 20 6f 6c 64 20 64 65 73 |re is an old des|
000004e0 69 67 6e 65 72 27 73 20 6a 6f 6b 65 20 74 68 61 |igner's joke tha|
000004f0 74 20 74 68 65 0d 64 69 66 66 65 72 65 6e 63 65 |t the.difference|
00000500 20 62 65 74 77 65 65 6e 20 73 74 61 74 69 63 20 | between static |
00000510 61 6e 64 20 64 79 6e 61 6d 69 63 20 72 61 6d 20 |and dynamic ram |
00000520 69 73 20 74 68 61 74 20 73 74 61 74 69 63 20 72 |is that static r|
00000530 61 6d 20 77 6f 72 6b 73 2e 0d 44 6f 6e 27 74 20 |am works..Don't |
00000540 6c 65 74 20 74 68 69 73 20 6e 6f 6e 73 65 6e 73 |let this nonsens|
00000550 65 20 70 72 65 76 65 6e 74 20 79 6f 75 20 62 75 |e prevent you bu|
00000560 79 69 6e 67 20 61 20 64 79 6e 61 6d 69 63 20 72 |ying a dynamic r|
00000570 61 6d 20 62 6f 61 72 64 2e 0d 0d 32 2e 20 20 50 |am board...2. P|
00000580 68 79 73 69 63 61 6c 20 73 77 69 74 63 68 69 6e |hysical switchin|
00000590 67 20 66 6f 72 20 72 65 61 64 20 61 6e 64 20 77 |g for read and w|
000005a0 72 69 74 65 20 70 72 6f 74 65 63 74 69 6f 6e 20 |rite protection |
000005b0 6f 66 20 74 68 65 20 53 57 52 20 69 73 0d 68 69 |of the SWR is.hi|
000005c0 67 68 6c 79 20 64 65 73 69 72 61 62 6c 65 2e 20 |ghly desirable. |
000005d0 52 65 61 64 20 70 72 6f 74 65 63 74 69 6f 6e 20 |Read protection |
000005e0 77 69 6c 6c 20 62 65 20 75 73 65 64 20 74 6f 20 |will be used to |
000005f0 73 77 69 74 63 68 20 6f 75 74 20 74 68 65 0d 6f |switch out the.o|
00000600 66 66 65 6e 64 69 6e 67 20 6d 65 6d 6f 72 79 20 |ffending memory |
00000610 77 68 65 6e 20 79 6f 75 20 6c 6f 61 64 20 61 6e |when you load an|
00000620 20 69 6e 76 61 6c 69 64 20 72 6f 6d 20 69 6d 61 | invalid rom ima|
00000630 67 65 20 77 68 69 63 68 20 63 61 75 73 65 73 20 |ge which causes |
00000640 74 68 65 0d 63 6f 6d 70 75 74 65 72 20 74 6f 20 |the.computer to |
00000650 68 61 6e 67 20 75 70 2e 20 57 72 69 74 65 20 70 |hang up. Write p|
00000660 72 6f 74 65 63 74 69 6f 6e 20 69 73 20 75 73 65 |rotection is use|
00000670 66 75 6c 20 69 66 20 79 6f 75 20 77 61 6e 74 20 |ful if you want |
00000680 74 6f 20 64 65 76 65 6c 6f 70 0d 72 6f 6d 20 69 |to develop.rom i|
00000690 6d 61 67 65 73 20 74 68 61 74 20 61 72 65 20 70 |mages that are p|
000006a0 72 6f 74 65 63 74 65 64 20 61 67 61 69 6e 73 74 |rotected against|
000006b0 20 72 75 6e 6e 69 6e 67 20 69 6e 20 53 57 52 2e | running in SWR.|
000006c0 20 53 6f 66 74 77 61 72 65 0d 73 77 69 74 63 68 | Software.switch|
000006d0 69 6e 67 20 6f 66 20 72 65 61 64 20 61 6e 64 20 |ing of read and |
000006e0 77 72 69 74 65 20 70 72 6f 74 65 63 74 69 6f 6e |write protection|
000006f0 20 69 73 20 61 20 70 6f 6f 72 20 73 75 62 73 74 | is a poor subst|
00000700 69 74 75 74 65 20 66 6f 72 20 72 65 61 6c 0d 73 |itute for real.s|
00000710 77 69 74 63 68 65 73 20 74 68 61 74 20 63 6c 69 |witches that cli|
00000720 63 6b 2e 0d 0d 33 2e 20 20 4c 6f 6f 6b 20 63 61 |ck...3. Look ca|
00000730 72 65 66 75 6c 6c 79 20 61 74 20 74 68 65 20 77 |refully at the w|
00000740 61 79 20 69 6e 20 77 68 69 63 68 20 66 6c 79 69 |ay in which flyi|
00000750 6e 67 20 6c 65 61 64 73 20 61 72 65 20 61 74 74 |ng leads are att|
00000760 61 63 68 65 64 20 74 6f 0d 74 68 65 20 6d 61 69 |ached to.the mai|
00000770 6e 20 63 6f 6d 70 75 74 65 72 20 63 69 72 63 75 |n computer circu|
00000780 69 74 20 62 6f 61 72 64 2e 20 43 6f 6d 70 61 72 |it board. Compar|
00000790 65 20 74 68 65 20 64 69 66 66 65 72 65 6e 74 20 |e the different |
000007a0 6d 65 74 68 6f 64 73 0d 6d 61 6e 75 66 61 63 74 |methods.manufact|
000007b0 75 72 65 72 73 20 75 73 65 2e 20 53 6f 6d 65 20 |urers use. Some |
000007c0 62 6f 61 72 64 73 20 75 73 65 20 71 75 69 74 65 |boards use quite|
000007d0 20 75 6e 70 72 6f 66 65 73 73 69 6f 6e 61 6c 20 | unprofessional |
000007e0 64 65 73 69 67 6e 0d 74 65 63 68 6e 69 71 75 65 |design.technique|
000007f0 73 2e 0d 0d 34 2e 20 20 42 61 74 74 65 72 79 20 |s...4. Battery |
00000800 62 61 63 6b 75 70 20 6f 66 20 53 57 52 20 69 73 |backup of SWR is|
00000810 20 75 73 65 66 75 6c 2c 20 62 75 74 20 6e 6f 74 | useful, but not|
00000820 20 65 73 73 65 6e 74 69 61 6c 2e 0d 0d 35 2e 20 | essential...5. |
00000830 20 4d 61 6e 79 20 53 57 52 20 62 6f 61 72 64 73 | Many SWR boards|
00000840 20 68 61 76 65 20 73 6f 63 6b 65 74 73 20 66 6f | have sockets fo|
00000850 72 20 65 78 74 72 61 20 72 6f 6d 73 2e 20 54 68 |r extra roms. Th|
00000860 65 20 42 42 43 20 42 20 4d 4f 53 20 77 69 6c 6c |e BBC B MOS will|
00000870 0d 73 75 70 70 6f 72 74 20 75 70 20 74 6f 20 73 |.support up to s|
00000880 69 78 74 65 65 6e 20 73 69 64 65 77 61 79 73 20 |ixteen sideways |
00000890 72 6f 6d 20 6f 72 20 72 61 6d 20 62 61 6e 6b 73 |rom or ram banks|
000008a0 2e 20 54 68 65 20 6d 61 69 6e 20 63 69 72 63 75 |. The main circu|
000008b0 69 74 0d 62 6f 61 72 64 20 68 61 73 20 6f 6e 6c |it.board has onl|
000008c0 79 20 66 6f 75 72 20 73 69 64 65 77 61 79 73 20 |y four sideways |
000008d0 72 6f 6d 20 73 6f 63 6b 65 74 73 2c 20 74 77 6f |rom sockets, two|
000008e0 20 6f 66 20 77 68 69 63 68 20 61 72 65 20 74 61 | of which are ta|
000008f0 6b 65 6e 20 75 70 0d 77 69 74 68 20 42 41 53 49 |ken up.with BASI|
00000900 43 20 61 6e 64 20 74 68 65 20 44 46 53 2e 20 54 |C and the DFS. T|
00000910 68 65 20 65 78 74 72 61 20 73 6f 63 6b 65 74 73 |he extra sockets|
00000920 20 6f 6e 20 61 20 73 69 64 65 77 61 79 73 20 72 | on a sideways r|
00000930 61 6d 2f 72 6f 6d 20 62 6f 61 72 64 0d 77 69 6c |am/rom board.wil|
00000940 6c 20 62 65 20 75 73 65 66 75 6c 20 69 66 20 79 |l be useful if y|
00000950 6f 75 20 68 61 76 65 20 6d 6f 72 65 20 72 6f 6d |ou have more rom|
00000960 73 20 74 68 61 6e 20 72 6f 6d 20 73 6f 63 6b 65 |s than rom socke|
00000970 74 73 2e 0d 0d 20 20 54 68 65 72 65 20 61 72 65 |ts... There are|
00000980 20 61 20 6e 75 6d 62 65 72 20 6f 66 20 6d 61 6e | a number of man|
00000990 75 66 61 63 74 75 72 65 72 73 20 77 68 6f 20 70 |ufacturers who p|
000009a0 72 6f 64 75 63 65 20 62 6f 61 72 64 73 20 77 68 |roduce boards wh|
000009b0 69 63 68 20 6d 65 65 74 0d 74 68 65 73 65 20 72 |ich meet.these r|
000009c0 65 71 75 69 72 65 6d 65 6e 74 73 20 74 6f 20 61 |equirements to a|
000009d0 20 67 72 65 61 74 65 72 20 6f 72 20 6c 65 73 73 | greater or less|
000009e0 65 72 20 65 78 74 65 6e 74 2e 20 57 68 69 63 68 |er extent. Which|
000009f0 20 6d 61 6e 75 66 61 63 74 75 72 65 72 0d 79 6f | manufacturer.yo|
00000a00 75 20 63 68 6f 6f 73 65 20 69 73 20 75 70 20 74 |u choose is up t|
00000a10 6f 20 79 6f 75 2e 20 59 6f 75 20 63 61 6e 20 62 |o you. You can b|
00000a20 65 20 73 75 72 65 20 74 68 61 74 20 61 6c 6c 20 |e sure that all |
00000a30 74 68 65 20 62 6f 61 72 64 73 20 70 72 6f 64 75 |the boards produ|
00000a40 63 65 64 0d 62 79 20 72 65 70 75 74 61 62 6c 65 |ced.by reputable|
00000a50 20 63 6f 6d 70 61 6e 69 65 73 20 77 69 6c 6c 20 | companies will |
00000a60 70 65 72 66 6f 72 6d 20 61 64 65 71 75 61 74 65 |perform adequate|
00000a70 6c 79 20 62 75 74 20 69 74 20 69 73 20 6e 6f 74 |ly but it is not|
00000a80 20 70 6f 73 73 69 62 6c 65 0d 74 6f 20 72 65 63 | possible.to rec|
00000a90 6f 6d 6d 65 6e 64 20 6f 6e 65 20 62 6f 61 72 64 |ommend one board|
00000aa0 20 61 73 20 62 65 74 74 65 72 20 69 6e 20 65 76 | as better in ev|
00000ab0 65 72 79 20 72 65 73 70 65 63 74 20 74 68 61 6e |ery respect than|
00000ac0 20 61 6e 79 20 6f 74 68 65 72 2e 0d 0d 20 20 57 | any other... W|
00000ad0 68 65 6e 20 79 6f 75 20 68 61 76 65 20 66 69 74 |hen you have fit|
00000ae0 74 65 64 20 74 68 65 20 75 70 67 72 61 64 65 20 |ted the upgrade |
00000af0 62 6f 61 72 64 20 69 6e 74 6f 20 79 6f 75 72 20 |board into your |
00000b00 63 6f 6d 70 75 74 65 72 20 79 6f 75 20 6d 69 67 |computer you mig|
00000b10 68 74 0d 77 61 6e 74 20 74 6f 20 73 74 6f 72 65 |ht.want to store|
00000b20 20 74 68 65 20 70 72 6f 67 72 61 6d 73 20 63 6f | the programs co|
00000b30 6e 74 61 69 6e 65 64 20 69 6e 20 79 6f 75 72 20 |ntained in your |
00000b40 72 6f 6d 73 20 6f 6e 20 64 69 73 63 20 6f 72 20 |roms on disc or |
00000b50 74 61 70 65 20 61 6e 64 0d 74 68 65 6e 20 6c 6f |tape and.then lo|
00000b60 61 64 20 61 6e 64 20 72 75 6e 20 74 68 65 20 72 |ad and run the r|
00000b70 6f 6d 20 69 6d 61 67 65 73 20 69 6e 20 53 57 52 |om images in SWR|
00000b80 2e 20 41 6c 6c 20 41 63 6f 72 6e 20 73 75 70 70 |. All Acorn supp|
00000b90 6f 72 74 65 64 20 6c 61 6e 67 75 61 67 65 73 0d |orted languages.|
00000ba0 77 69 6c 6c 20 72 75 6e 20 69 6e 20 75 6e 70 72 |will run in unpr|
00000bb0 6f 74 65 63 74 65 64 20 53 57 52 20 61 6e 64 20 |otected SWR and |
00000bc0 6d 6f 73 74 20 72 6f 6d 20 69 6d 61 67 65 73 20 |most rom images |
00000bd0 77 69 6c 6c 20 72 75 6e 20 69 6e 20 77 72 69 74 |will run in writ|
00000be0 65 0d 70 72 6f 74 65 63 74 65 64 20 53 57 52 2e |e.protected SWR.|
00000bf0 0d 0d 20 20 57 68 65 72 65 20 74 68 65 20 63 6f |.. Where the co|
00000c00 70 79 72 69 67 68 74 20 6f 66 20 74 68 65 20 73 |pyright of the s|
00000c10 6f 66 74 77 61 72 65 20 20 63 6f 6e 74 61 69 6e |oftware contain|
00000c20 65 64 20 69 6e 20 61 20 72 6f 6d 20 69 73 20 6e |ed in a rom is n|
00000c30 6f 74 20 6f 77 6e 65 64 0d 62 79 20 41 63 6f 72 |ot owned.by Acor|
00000c40 6e 2c 20 73 70 65 63 69 66 69 63 20 70 65 72 6d |n, specific perm|
00000c50 69 73 73 69 6f 6e 20 6d 75 73 74 20 62 65 20 6f |ission must be o|
00000c60 62 74 61 69 6e 65 64 20 66 72 6f 6d 20 74 68 65 |btained from the|
00000c70 20 6f 77 6e 65 72 20 6f 66 20 74 68 65 0d 63 6f | owner of the.co|
00000c80 70 79 72 69 67 68 74 20 62 65 66 6f 72 65 20 63 |pyright before c|
00000c90 6f 70 79 69 6e 67 20 69 74 20 6f 6e 74 6f 20 64 |opying it onto d|
00000ca0 69 73 63 20 6f 72 20 74 61 70 65 2e 0d 0d 20 20 |isc or tape... |
00000cb0 49 6e 20 41 63 6f 72 6e 27 73 20 55 73 65 72 20 |In Acorn's User |
00000cc0 47 75 69 64 65 20 28 50 61 72 74 20 6e 6f 2e 20 |Guide (Part no. |
00000cd0 34 30 38 30 30 30 2c 20 49 73 73 75 65 20 6e 6f |408000, Issue no|
00000ce0 2e 20 32 2c 20 4d 61 72 63 68 20 31 39 38 34 2c |. 2, March 1984,|
00000cf0 0d 70 61 67 65 20 32 30 29 20 69 74 20 73 74 61 |.page 20) it sta|
00000d00 74 65 73 20 22 2e 2e 2e 20 79 6f 75 20 63 61 6e |tes "... you can|
00000d10 20 6b 65 65 70 20 61 20 6c 69 62 72 61 72 79 20 | keep a library |
00000d20 6f 66 20 70 61 67 65 64 20 72 6f 6d 73 20 6f 6e |of paged roms on|
00000d30 20 64 69 73 63 2c 0d 77 68 69 63 68 20 63 61 6e | disc,.which can|
00000d40 20 62 65 20 63 61 6c 6c 65 64 20 75 70 20 69 6e | be called up in|
00000d50 20 74 68 65 20 73 61 6d 65 20 77 61 79 20 61 73 | the same way as|
00000d60 20 72 6f 6d 73 20 69 6e 73 74 61 6c 6c 65 64 20 | roms installed |
00000d70 69 6e 73 69 64 65 20 74 68 65 0d 42 42 43 20 4d |inside the.BBC M|
00000d80 69 63 72 6f 63 6f 6d 70 75 74 65 72 2e 20 48 6f |icrocomputer. Ho|
00000d90 77 65 76 65 72 2c 20 69 6e 20 75 73 69 6e 67 20 |wever, in using |
00000da0 74 68 69 73 20 66 61 63 69 6c 69 74 79 20 79 6f |this facility yo|
00000db0 75 20 6d 75 73 74 20 65 6e 73 75 72 65 0d 74 68 |u must ensure.th|
00000dc0 61 74 20 79 6f 75 20 64 6f 20 6e 6f 74 20 69 6e |at you do not in|
00000dd0 66 72 69 6e 67 65 20 74 68 65 20 72 69 67 68 74 |fringe the right|
00000de0 73 20 6f 66 20 74 68 65 20 6f 77 6e 65 72 20 6f |s of the owner o|
00000df0 66 20 74 68 65 20 63 6f 70 79 72 69 67 68 74 20 |f the copyright |
00000e00 6f 66 0d 74 68 65 20 70 72 6f 67 72 61 6d 20 63 |of.the program c|
00000e10 6f 6e 74 61 69 6e 65 64 20 69 6e 20 74 68 65 20 |ontained in the |
00000e20 72 6f 6d 22 2e 0d 0d 20 20 41 73 20 6c 6f 6e 67 |rom"... As long|
00000e30 20 61 73 20 79 6f 75 20 64 6f 20 6e 6f 74 20 69 | as you do not i|
00000e40 6e 66 72 69 6e 67 65 20 74 68 65 20 72 69 67 68 |nfringe the righ|
00000e50 74 73 20 6f 66 20 74 68 65 20 6f 77 6e 65 72 20 |ts of the owner |
00000e60 6f 66 20 74 68 65 0d 63 6f 70 79 72 69 67 68 74 |of the.copyright|
00000e70 20 6f 66 20 74 68 65 20 70 72 6f 67 72 61 6d 2c | of the program,|
00000e80 20 72 6f 6d 73 20 63 61 6e 20 62 65 20 73 61 76 | roms can be sav|
00000e90 65 64 20 6f 6e 74 6f 20 61 20 6c 69 62 72 61 72 |ed onto a librar|
00000ea0 79 20 64 69 73 63 20 61 6e 64 0d 72 75 6e 20 69 |y disc and.run i|
00000eb0 6e 20 72 61 6d 2e 20 53 6f 6d 65 20 73 6f 66 74 |n ram. Some soft|
00000ec0 77 61 72 65 20 70 72 6f 64 75 63 65 72 73 20 74 |ware producers t|
00000ed0 61 6b 65 20 61 20 6c 65 73 73 20 65 6e 6c 69 67 |ake a less enlig|
00000ee0 68 74 65 6e 65 64 20 76 69 65 77 20 74 68 61 6e |htened view than|
00000ef0 0d 41 63 6f 72 6e 20 74 61 6b 65 20 74 6f 20 72 |.Acorn take to r|
00000f00 75 6e 6e 69 6e 67 20 74 68 65 69 72 20 72 6f 6d |unning their rom|
00000f10 73 20 69 6e 20 53 57 52 20 61 6e 64 20 61 74 74 |s in SWR and att|
00000f20 65 6d 70 74 20 74 6f 20 70 72 6f 74 65 63 74 20 |empt to protect |
00000f30 74 68 65 6d 0d 61 67 61 69 6e 73 74 20 69 74 2e |them.against it.|
00000f40 20 4d 6f 73 74 20 6f 66 20 74 68 69 73 20 70 72 | Most of this pr|
00000f50 6f 74 65 63 74 69 6f 6e 20 64 6f 65 73 20 6c 69 |otection does li|
00000f60 74 74 6c 65 20 74 6f 20 64 65 74 65 72 20 70 72 |ttle to deter pr|
00000f70 6f 66 65 73 73 69 6f 6e 61 6c 0d 73 6f 66 74 77 |ofessional.softw|
00000f80 61 72 65 20 70 69 72 61 74 65 73 20 62 75 74 20 |are pirates but |
00000f90 69 74 20 73 68 6f 75 6c 64 20 62 65 20 74 61 6b |it should be tak|
00000fa0 65 6e 20 61 73 20 61 6e 20 69 6e 64 69 63 61 74 |en as an indicat|
00000fb0 6f 72 20 6f 66 20 74 68 65 0d 63 6f 70 79 72 69 |or of the.copyri|
00000fc0 67 68 74 20 6f 77 6e 65 72 27 73 20 75 6e 77 69 |ght owner's unwi|
00000fd0 6c 6c 69 6e 67 6e 65 73 73 20 74 6f 20 61 6c 6c |llingness to all|
00000fe0 6f 77 20 68 69 73 20 6f 72 20 68 65 72 20 77 6f |ow his or her wo|
00000ff0 72 6b 20 74 6f 20 62 65 20 75 73 65 64 20 69 6e |rk to be used in|
00001000 0d 53 57 52 2e 0d 0d 20 20 49 66 20 79 6f 75 20 |.SWR... If you |
00001010 77 61 6e 74 20 74 6f 20 65 6e 73 75 72 65 20 74 |want to ensure t|
00001020 68 61 74 20 79 6f 75 72 20 6f 77 6e 20 77 6f 72 |hat your own wor|
00001030 6b 20 77 69 6c 6c 20 6f 6e 6c 79 20 72 75 6e 20 |k will only run |
00001040 69 6e 20 65 70 72 6f 6d 73 20 61 6e 64 0d 6e 6f |in eproms and.no|
00001050 74 20 69 6e 20 53 57 52 20 74 68 65 72 65 20 61 |t in SWR there a|
00001060 72 65 20 61 20 6e 75 6d 62 65 72 20 6f 66 20 74 |re a number of t|
00001070 65 63 68 6e 69 71 75 65 73 20 79 6f 75 20 63 61 |echniques you ca|
00001080 6e 20 74 72 79 2e 20 41 6e 20 38 6b 20 72 6f 6d |n try. An 8k rom|
00001090 0d 69 6d 61 67 65 20 69 73 20 64 75 70 6c 69 63 |.image is duplic|
000010a0 61 74 65 64 20 66 72 6f 6d 20 26 41 30 30 30 20 |ated from &A000 |
000010b0 61 6e 64 20 6f 6e 65 20 6f 66 20 74 68 65 20 6d |and one of the m|
000010c0 65 74 68 6f 64 73 20 6f 66 20 70 72 6f 74 65 63 |ethods of protec|
000010d0 74 69 6e 67 20 38 6b 0d 72 6f 6d 20 69 6d 61 67 |ting 8k.rom imag|
000010e0 65 73 20 69 73 20 74 6f 20 61 64 64 20 26 32 30 |es is to add &20|
000010f0 30 30 20 74 6f 20 74 68 65 20 73 75 62 72 6f 75 |00 to the subrou|
00001100 74 69 6e 65 20 61 6e 64 20 6a 75 6d 70 20 61 64 |tine and jump ad|
00001110 64 72 65 73 73 65 73 2e 0d 41 6e 6f 74 68 65 72 |dresses..Another|
00001120 2c 20 66 61 72 20 6c 65 73 73 20 63 6f 6d 6d 6f |, far less commo|
00001130 6e 2c 20 6d 65 74 68 6f 64 20 69 73 20 74 6f 20 |n, method is to |
00001140 70 72 65 76 65 6e 74 20 74 68 65 20 72 6f 6d 20 |prevent the rom |
00001150 69 6d 61 67 65 20 72 75 6e 6e 69 6e 67 0d 69 6e |image running.in|
00001160 20 73 6f 63 6b 65 74 20 26 30 46 2e 20 54 68 69 | socket &0F. Thi|
00001170 73 20 73 6f 63 6b 65 74 20 69 73 20 63 6f 6d 6d |s socket is comm|
00001180 6f 6e 6c 79 20 75 73 65 64 20 66 6f 72 20 53 57 |only used for SW|
00001190 52 20 6f 6e 20 72 6f 6d 20 62 6f 61 72 64 73 20 |R on rom boards |
000011a0 61 6e 64 0d 74 68 65 20 6f 6e 6c 79 20 77 61 79 |and.the only way|
000011b0 20 74 6f 20 67 65 74 20 74 68 65 73 65 20 72 6f | to get these ro|
000011c0 6d 20 69 6d 61 67 65 73 20 74 6f 20 72 75 6e 20 |m images to run |
000011d0 69 6e 20 73 6f 63 6b 65 74 20 26 30 46 20 69 73 |in socket &0F is|
000011e0 20 74 6f 0d 64 69 73 61 73 73 65 6d 62 6c 65 20 | to.disassemble |
000011f0 61 6e 64 20 6d 6f 64 69 66 79 20 74 68 65 6d 2e |and modify them.|
00001200 20 57 68 65 6e 20 79 6f 75 20 68 61 76 65 20 63 | When you have c|
00001210 6f 6d 70 6c 65 74 65 64 20 74 68 69 73 20 63 6f |ompleted this co|
00001220 75 72 73 65 20 79 6f 75 0d 77 69 6c 6c 20 63 65 |urse you.will ce|
00001230 72 74 61 69 6e 6c 79 20 6b 6e 6f 77 20 77 68 61 |rtainly know wha|
00001240 74 20 74 6f 20 6c 6f 6f 6b 20 66 6f 72 20 69 6e |t to look for in|
00001250 20 61 20 72 6f 6d 20 64 69 73 61 73 73 65 6d 62 | a rom disassemb|
00001260 6c 79 20 69 66 20 79 6f 75 0d 77 61 6e 74 65 64 |ly if you.wanted|
00001270 20 74 6f 20 64 6f 20 74 68 69 73 20 62 75 74 20 | to do this but |
00001280 69 74 20 69 73 20 71 75 69 74 65 20 61 20 67 6f |it is quite a go|
00001290 6f 64 20 77 61 79 20 6f 66 20 64 65 74 65 72 69 |od way of deteri|
000012a0 6e 67 20 6d 6f 73 74 20 61 6d 61 74 65 75 72 0d |ng most amateur.|
000012b0 72 6f 6d 20 70 69 6c 66 65 72 65 72 73 2e 0d 0d |rom pilferers...|
000012c0 20 20 49 20 77 69 6c 6c 20 6e 6f 77 20 62 65 67 | I will now beg|
000012d0 69 6e 20 74 6f 20 65 78 70 6c 6f 72 65 20 74 68 |in to explore th|
000012e0 65 20 70 72 6f 67 72 61 6d 6d 69 6e 67 20 74 65 |e programming te|
000012f0 63 68 6e 69 71 75 65 73 20 6e 65 65 64 65 64 20 |chniques needed |
00001300 74 6f 20 75 73 65 0d 53 57 52 2e 20 54 68 65 72 |to use.SWR. Ther|
00001310 65 20 61 72 65 20 61 20 6e 75 6d 62 65 72 20 6f |e are a number o|
00001320 66 20 4d 4f 53 20 73 75 62 72 6f 75 74 69 6e 65 |f MOS subroutine|
00001330 73 2c 20 6d 65 6d 6f 72 79 20 6c 6f 63 61 74 69 |s, memory locati|
00001340 6f 6e 73 20 61 6e 64 0d 72 65 67 69 73 74 65 72 |ons and.register|
00001350 73 20 61 73 73 6f 63 69 61 74 65 64 20 77 69 74 |s associated wit|
00001360 68 20 53 57 52 2e 20 52 61 74 68 65 72 20 74 68 |h SWR. Rather th|
00001370 61 6e 20 65 78 61 6d 69 6e 65 20 74 68 65 6d 20 |an examine them |
00001380 61 6c 6c 20 6e 6f 77 20 49 20 77 69 6c 6c 0d 63 |all now I will.c|
00001390 6f 6e 73 69 64 65 72 20 74 68 65 20 63 61 6c 6c |onsider the call|
000013a0 73 20 61 6e 64 20 6c 6f 63 61 74 69 6f 6e 73 20 |s and locations |
000013b0 61 73 20 74 68 65 79 20 61 72 69 73 65 20 74 68 |as they arise th|
000013c0 72 6f 75 67 68 6f 75 74 20 74 68 65 20 63 6f 75 |roughout the cou|
000013d0 72 73 65 2e 0d 49 6e 20 74 68 69 73 20 6d 6f 64 |rse..In this mod|
000013e0 75 6c 65 20 49 20 77 69 6c 6c 20 6c 6f 6f 6b 20 |ule I will look |
000013f0 61 74 20 74 68 65 20 70 61 67 65 64 20 72 6f 6d |at the paged rom|
00001400 20 73 65 6c 65 63 74 20 72 65 67 69 73 74 65 72 | select register|
00001410 20 61 74 20 26 46 45 33 30 2c 0d 74 68 65 20 70 | at &FE30,.the p|
00001420 61 67 65 64 20 6d 65 6d 6f 72 79 20 73 65 6c 65 |aged memory sele|
00001430 63 74 20 72 65 67 69 73 74 65 72 20 61 74 20 26 |ct register at &|
00001440 46 45 33 34 2c 20 74 68 65 20 4d 4f 53 20 73 75 |FE34, the MOS su|
00001450 62 72 6f 75 74 69 6e 65 20 4f 73 72 64 72 6d 2c |broutine Osrdrm,|
00001460 0d 61 6e 64 20 4f 73 62 79 74 65 73 20 26 37 32 |.and Osbytes &72|
00001470 20 61 6e 64 20 26 41 41 2e 0d 0d 20 20 54 68 65 | and &AA... The|
00001480 72 65 20 61 72 65 20 64 69 66 66 65 72 65 6e 63 |re are differenc|
00001490 65 73 20 69 6e 20 74 68 65 20 77 61 79 20 69 6e |es in the way in|
000014a0 20 77 68 69 63 68 20 74 68 65 20 70 61 67 65 64 | which the paged|
000014b0 20 72 6f 6d 20 73 65 6c 65 63 74 0d 72 65 67 69 | rom select.regi|
000014c0 73 74 65 72 20 61 6e 64 20 74 68 65 20 70 61 67 |ster and the pag|
000014d0 65 64 20 6d 65 6d 6f 72 79 20 73 65 6c 65 63 74 |ed memory select|
000014e0 20 72 65 67 69 73 74 65 72 20 61 72 65 20 75 73 | register are us|
000014f0 65 64 20 69 6e 20 74 68 65 20 42 42 43 20 42 2c |ed in the BBC B,|
00001500 0d 74 68 65 20 42 42 43 20 42 2b 20 61 6e 64 20 |.the BBC B+ and |
00001510 74 68 65 20 4d 61 73 74 65 72 20 63 6f 6d 70 75 |the Master compu|
00001520 74 65 72 73 2e 20 54 68 65 20 72 65 61 73 6f 6e |ters. The reason|
00001530 20 66 6f 72 20 74 68 65 20 64 69 66 66 65 72 65 | for the differe|
00001540 6e 63 65 73 0d 63 61 6e 20 62 65 20 73 65 65 6e |nces.can be seen|
00001550 20 62 79 20 65 78 61 6d 69 6e 69 6e 67 20 74 68 | by examining th|
00001560 65 20 6d 65 6d 6f 72 79 20 6d 61 70 73 20 6f 66 |e memory maps of|
00001570 20 74 68 65 73 65 20 6d 61 63 68 69 6e 65 73 20 | these machines |
00001580 28 66 69 67 75 72 65 73 0d 31 2e 31 2c 20 31 2e |(figures.1.1, 1.|
00001590 32 20 61 6e 64 20 31 2e 33 29 2e 0d 0d 0d 0d 20 |2 and 1.3)..... |
000015a0 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | |
000015b0 20 20 20 20 20 20 20 20 20 20 20 20 20 26 46 46 | &FF|
000015c0 46 46 20 2b 2d 2d 2d 2d 2d 2d 2d 2b 20 26 46 46 |FF +-------+ &FF|
000015d0 46 46 0d 20 20 20 20 20 20 20 20 20 20 20 20 20 |FF. |
000015e0 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | |
000015f0 20 20 20 20 20 20 20 21 20 20 20 20 20 20 20 21 | ! !|
00001600 20 20 0d 20 20 20 20 20 20 20 20 20 20 20 20 20 | . |
00001610 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | |
00001620 20 20 20 20 20 20 20 21 20 20 4d 4f 53 20 20 21 | ! MOS !|
00001630 0d 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 |. |
00001640 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | |
00001650 20 20 20 20 20 21 20 20 20 20 20 20 20 21 20 20 | ! ! |
00001660 20 20 20 20 20 20 20 0d 20 20 20 20 26 42 46 46 | . &BFF|
00001670 46 20 2d 2d 2b 2d 2d 2d 2d 2d 2d 2d 2b 2d 2d 2d |F --+-------+---|
00001680 2d 2d 2d 2d 2b 2d 2d 2d 2d 2d 2d 2d 2b 2d 2d 2d |----+-------+---|
00001690 2d 2d 2d 2d 2b 20 26 43 30 30 30 0d 20 20 20 20 |----+ &C000. |
000016a0 20 20 20 20 20 20 20 20 21 20 52 4f 4d 20 26 43 | ! ROM &C|
000016b0 21 20 52 4f 4d 20 26 44 21 20 52 4f 4d 20 26 45 |! ROM &D! ROM &E|
000016c0 21 20 52 4f 4d 20 26 46 21 0d 20 20 20 20 20 20 |! ROM &F!. |
000016d0 20 20 20 20 20 20 21 20 20 20 20 20 20 20 21 20 | ! ! |
*
000016f0 20 20 20 20 20 20 21 0d 20 20 20 20 20 20 20 20 | !. |
00001700 20 20 20 20 21 20 20 20 20 20 20 20 21 20 20 20 | ! ! |
00001710 20 20 20 20 21 20 20 44 46 53 20 20 21 20 42 41 | ! DFS ! BA|
00001720 53 49 43 20 21 0d 20 20 20 20 26 38 30 30 30 20 |SIC !. &8000 |
00001730 2d 2d 2b 2d 2d 2d 2d 2d 2d 2d 2b 2d 2d 2d 2d 2d |--+-------+-----|
*
00001750 2d 2d 2b 20 26 37 46 46 46 0d 20 20 20 20 55 70 |--+ &7FFF. Up|
00001760 20 74 6f 20 31 36 20 73 69 64 65 77 61 79 73 20 | to 16 sideways |
00001770 72 6f 6d 2f 72 61 6d 20 62 61 6e 6b 73 20 21 20 |rom/ram banks ! |
00001780 20 20 20 20 20 20 21 0d 20 20 20 20 20 20 20 20 | !. |
00001790 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | |
000017a0 20 20 20 20 20 20 20 20 20 20 20 20 21 20 20 55 | ! U|
000017b0 73 65 72 20 21 0d 20 20 20 20 20 20 20 20 20 20 |ser !. |
000017c0 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | |
000017d0 20 20 20 20 20 20 20 20 20 20 21 20 6d 65 6d 6f | ! memo|
000017e0 72 79 21 0d 20 20 20 20 20 20 20 20 20 20 20 20 |ry!. |
000017f0 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | |
00001800 20 20 20 20 20 20 20 20 21 20 20 20 20 20 20 20 | ! |
00001810 21 0d 20 20 20 20 20 20 20 20 20 20 20 20 20 20 |!. |
00001820 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | |
00001830 20 20 20 20 20 20 21 20 20 20 20 20 20 20 21 0d | ! !.|
00001840 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | |
00001850 20 20 20 20 20 20 20 20 20 20 20 20 20 20 26 31 | &1|
00001860 39 30 30 20 2b 2d 2d 2d 2d 2d 2d 2d 2b 20 4f 73 |900 +-------+ Os|
00001870 68 77 6d 20 0d 20 20 20 20 20 20 20 20 20 20 20 |hwm . |
00001880 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | |
00001890 20 20 20 20 20 20 20 20 20 21 20 20 20 20 20 20 | ! |
000018a0 20 21 20 20 20 20 20 20 20 0d 20 20 20 20 20 20 | ! . |
000018b0 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | |
000018c0 20 20 20 20 20 20 20 20 26 30 30 30 30 20 2b 2d | &0000 +-|
000018d0 2d 2d 2d 2d 2d 2d 2b 20 26 30 30 30 30 0d 0d 46 |------+ &0000..F|
000018e0 69 67 75 72 65 20 31 2e 31 20 4d 65 6d 6f 72 79 |igure 1.1 Memory|
000018f0 20 6d 61 70 20 6f 66 20 74 68 65 20 42 42 43 20 | map of the BBC |
00001900 42 0d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d |B.--------------|
00001910 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d |----------------|
00001920 2d 2d 2d 2d 0d 0d 0d 20 20 54 68 65 20 42 42 43 |----... The BBC|
00001930 20 42 20 4d 4f 53 20 73 75 70 70 6f 72 74 73 20 | B MOS supports |
00001940 75 70 20 74 6f 20 73 69 78 74 65 65 6e 20 70 61 |up to sixteen pa|
00001950 67 65 64 20 72 6f 6d 73 20 61 6c 74 68 6f 75 67 |ged roms althoug|
00001960 68 20 61 6e 0d 65 78 70 61 6e 73 69 6f 6e 20 62 |h an.expansion b|
00001970 6f 61 72 64 20 69 73 20 72 65 71 75 69 72 65 64 |oard is required|
00001980 20 69 66 20 6d 6f 72 65 20 74 68 61 6e 20 66 6f | if more than fo|
00001990 75 72 20 72 6f 6d 73 20 61 72 65 20 74 6f 20 62 |ur roms are to b|
000019a0 65 20 75 73 65 64 2e 20 54 68 65 0d 70 61 67 65 |e used. The.page|
000019b0 64 20 72 6f 6d 20 73 65 6c 65 63 74 20 72 65 67 |d rom select reg|
000019c0 69 73 74 65 72 20 61 74 20 26 46 45 33 30 20 69 |ister at &FE30 i|
000019d0 73 20 61 20 34 20 62 69 74 20 77 72 69 74 65 20 |s a 4 bit write |
000019e0 6f 6e 6c 79 20 72 65 67 69 73 74 65 72 0d 77 68 |only register.wh|
000019f0 69 63 68 20 64 65 74 65 72 6d 69 6e 65 73 20 77 |ich determines w|
00001a00 68 69 63 68 20 6f 66 20 74 68 65 20 31 36 20 72 |hich of the 16 r|
00001a10 6f 6d 73 20 69 73 20 73 77 69 74 63 68 65 64 20 |oms is switched |
00001a20 69 6e 74 6f 20 74 68 65 20 6d 61 69 6e 20 6d 65 |into the main me|
00001a30 6d 6f 72 79 0d 6d 61 70 2e 20 49 66 20 79 6f 75 |mory.map. If you|
00001a40 20 77 61 6e 74 20 74 6f 20 72 65 61 64 20 74 68 | want to read th|
00001a50 65 20 63 6f 6e 74 65 6e 74 73 20 6f 66 20 74 68 |e contents of th|
00001a60 69 73 20 72 65 67 69 73 74 65 72 20 79 6f 75 20 |is register you |
00001a70 73 68 6f 75 6c 64 20 72 65 61 64 0d 74 68 65 20 |should read.the |
00001a80 7a 65 72 6f 20 70 61 67 65 20 63 6f 70 79 20 6f |zero page copy o|
00001a90 66 20 69 74 20 61 74 20 26 46 34 2e 20 54 68 65 |f it at &F4. The|
00001aa0 20 6d 6f 73 74 20 73 69 67 6e 69 66 69 63 61 6e | most significan|
00001ab0 74 20 6e 79 62 62 6c 65 20 6f 66 20 74 68 65 0d |t nybble of the.|
00001ac0 70 61 67 65 64 20 72 6f 6d 20 73 65 6c 65 63 74 |paged rom select|
00001ad0 20 72 65 67 69 73 74 65 72 20 69 73 20 6e 6f 74 | register is not|
00001ae0 20 75 73 65 64 20 6f 6e 20 74 68 65 20 42 42 43 | used on the BBC|
00001af0 20 42 2e 0d 0d 0d 0d 20 20 20 20 20 20 20 20 20 | B..... |
00001b00 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | |
00001b10 20 20 20 20 20 26 46 46 46 46 20 2b 2d 2d 2d 2d | &FFFF +----|
00001b20 2d 2d 2d 2b 20 26 46 46 46 46 0d 20 20 20 20 20 |---+ &FFFF. |
00001b30 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | |
00001b40 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 21 | !|
00001b50 20 20 20 20 20 20 20 21 20 20 0d 20 20 20 20 20 | ! . |
00001b60 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | |
00001b70 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 21 | !|
00001b80 20 20 4d 4f 53 20 20 21 0d 20 20 20 20 20 20 20 | MOS !. |
00001b90 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | |
00001ba0 20 20 20 20 20 20 20 20 20 20 20 20 20 21 20 20 | ! |
00001bb0 20 20 20 20 20 21 20 20 20 20 20 20 20 20 20 0d | ! .|
00001bc0 20 20 20 20 26 42 46 46 46 20 2d 2d 2b 2d 2d 2d | &BFFF --+---|
00001bd0 2d 2d 2d 2d 2b 2d 2d 2d 2d 2d 2d 2d 2b 2d 2d 2d |----+-------+---|
00001be0 2d 2d 2d 2d 2b 2d 2d 2d 2d 2d 2d 2d 2b 20 26 43 |----+-------+ &C|
00001bf0 30 30 30 0d 20 20 20 20 20 20 20 20 20 20 20 20 |000. |
00001c00 21 20 52 4f 4d 20 26 43 21 20 52 4f 4d 20 26 44 |! ROM &C! ROM &D|
00001c10 21 20 52 4f 4d 20 26 45 21 20 52 4f 4d 20 26 46 |! ROM &E! ROM &F|
00001c20 2b 2d 2d 2d 2d 2d 2d 2d 2b 20 26 41 46 46 46 0d |+-------+ &AFFF.|
00001c30 20 20 20 20 20 20 20 20 20 20 20 20 21 20 20 20 | ! |
00001c40 20 20 20 20 21 20 20 20 20 20 20 20 21 20 20 20 | ! ! |
00001c50 20 20 20 20 21 20 20 20 20 20 20 20 21 20 50 61 | ! ! Pa|
00001c60 67 65 64 20 21 0d 20 20 20 20 20 20 20 20 20 20 |ged !. |
00001c70 20 20 21 20 20 20 20 20 20 20 21 20 20 20 20 20 | ! ! |
00001c80 20 20 21 20 20 44 46 53 20 20 21 20 42 41 53 49 | ! DFS ! BASI|
00001c90 43 20 21 20 6d 65 6d 6f 72 79 21 20 0d 20 20 20 |C ! memory! . |
00001ca0 20 26 38 30 30 30 20 2d 2d 2b 2d 2d 2d 2d 2d 2d | &8000 --+------|
00001cb0 2d 2b 2d 2d 2d 2d 2d 2d 2d 2b 2d 2d 2d 2d 2d 2d |-+-------+------|
*
00001cd0 2d 2b 20 26 38 30 30 30 0d 20 20 20 20 55 70 20 |-+ &8000. Up |
00001ce0 74 6f 20 31 36 20 73 69 64 65 77 61 79 73 20 72 |to 16 sideways r|
00001cf0 6f 6d 2f 72 61 6d 20 62 61 6e 6b 73 20 21 20 20 |om/ram banks ! |
00001d00 20 20 20 20 20 21 20 20 20 20 20 20 20 21 0d 20 | ! !. |
00001d10 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | |
*
00001d30 20 20 20 21 20 20 55 73 65 72 20 21 20 53 68 61 | ! User ! Sha|
00001d40 64 6f 77 21 0d 20 20 20 20 20 20 20 20 20 20 20 |dow!. |
00001d50 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | |
00001d60 20 20 20 20 20 20 20 20 20 21 20 6d 65 6d 6f 72 | ! memor|
00001d70 79 21 20 20 72 61 6d 20 20 21 0d 20 20 20 20 20 |y! ram !. |
00001d80 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | |
00001d90 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 21 | !|
00001da0 20 20 20 20 20 20 20 21 20 20 20 20 20 20 20 21 | ! !|
00001db0 0d 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 |. |
00001dc0 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | |
00001dd0 20 20 20 20 20 21 20 20 20 20 20 20 20 2b 2d 2d | ! +--|
00001de0 2d 2d 2d 2d 2d 2b 20 26 33 30 30 30 0d 20 20 20 |-----+ &3000. |
00001df0 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | |
00001e00 20 20 20 20 20 20 20 20 20 20 20 26 31 39 30 30 | &1900|
00001e10 20 2b 2d 2d 2d 2d 2d 2d 2d 2b 20 4f 73 68 77 6d | +-------+ Oshwm|
00001e20 20 0d 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | . |
00001e30 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | |
00001e40 20 20 20 20 20 20 21 20 20 20 20 20 20 20 21 20 | ! ! |
00001e50 20 20 20 20 20 20 0d 20 20 20 20 20 20 20 20 20 | . |
00001e60 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | |
00001e70 20 20 20 20 20 26 30 30 30 30 20 2b 2d 2d 2d 2d | &0000 +----|
00001e80 2d 2d 2d 2b 20 26 30 30 30 30 0d 0d 46 69 67 75 |---+ &0000..Figu|
00001e90 72 65 20 31 2e 32 20 4d 65 6d 6f 72 79 20 6d 61 |re 1.2 Memory ma|
00001ea0 70 20 6f 66 20 74 68 65 20 42 42 43 20 42 2b 0d |p of the BBC B+.|
00001eb0 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d |----------------|
*
00001ed0 2d 2d 2d 0d 0d 0d 20 20 54 68 65 20 42 42 43 20 |---... The BBC |
00001ee0 42 2b 20 68 61 73 20 61 20 73 69 6d 69 6c 61 72 |B+ has a similar|
00001ef0 20 6d 65 6d 6f 72 79 20 6d 61 70 20 74 6f 20 74 | memory map to t|
00001f00 68 65 20 42 42 43 20 42 20 62 75 74 20 69 6e 20 |he BBC B but in |
00001f10 61 64 64 69 74 69 6f 6e 20 74 6f 0d 74 68 65 20 |addition to.the |
00001f20 70 61 67 65 64 20 72 6f 6d 73 20 69 74 20 61 6c |paged roms it al|
00001f30 73 6f 20 73 75 70 70 6f 72 74 73 20 70 61 67 65 |so supports page|
00001f40 64 20 6f 72 20 73 68 61 64 6f 77 20 6d 65 6d 6f |d or shadow memo|
00001f50 72 79 2e 20 54 68 65 20 70 61 67 65 64 0d 6d 65 |ry. The paged.me|
00001f60 6d 6f 72 79 20 28 73 68 61 64 6f 77 20 72 61 6d |mory (shadow ram|
00001f70 29 20 73 65 6c 65 63 74 20 72 65 67 69 73 74 65 |) select registe|
00001f80 72 20 61 74 20 26 46 45 33 34 20 69 73 20 75 73 |r at &FE34 is us|
00001f90 65 64 20 74 6f 20 64 65 74 65 72 6d 69 6e 65 0d |ed to determine.|
00001fa0 77 68 65 74 68 65 72 20 6f 72 20 6e 6f 74 20 74 |whether or not t|
00001fb0 68 65 20 73 68 61 64 6f 77 20 72 61 6d 20 69 73 |he shadow ram is|
00001fc0 20 75 73 65 64 20 61 73 20 73 63 72 65 65 6e 20 | used as screen |
00001fd0 6d 65 6d 6f 72 79 2e 20 54 68 69 73 20 72 65 67 |memory. This reg|
00001fe0 69 73 74 65 72 0d 73 68 6f 75 6c 64 20 6f 6e 6c |ister.should onl|
00001ff0 79 20 62 65 20 61 6c 74 65 72 65 64 20 75 73 69 |y be altered usi|
00002000 6e 67 20 4f 73 62 79 74 65 20 26 37 32 20 28 2a |ng Osbyte &72 (*|
00002010 46 58 31 31 34 29 20 6f 72 20 74 68 65 20 63 6f |FX114) or the co|
00002020 6d 6d 61 6e 64 0d 2a 53 48 41 44 4f 57 2e 20 54 |mmand.*SHADOW. T|
00002030 68 65 20 42 42 43 20 42 2b 20 68 61 73 20 61 20 |he BBC B+ has a |
00002040 22 73 70 61 72 65 22 20 31 32 6b 20 6f 66 20 70 |"spare" 12k of p|
00002050 61 67 65 64 20 6d 65 6d 6f 72 79 20 66 72 6f 6d |aged memory from|
00002060 20 26 38 30 30 30 20 74 6f 0d 26 41 46 46 46 2e | &8000 to.&AFFF.|
00002070 20 54 68 69 73 20 63 61 6e 20 62 65 20 73 77 69 | This can be swi|
00002080 74 63 68 65 64 20 69 6e 20 6f 72 20 6f 75 74 20 |tched in or out |
00002090 6f 66 20 74 68 65 20 6d 61 69 6e 20 6d 65 6d 6f |of the main memo|
000020a0 72 79 20 6d 61 70 20 75 73 69 6e 67 20 74 68 65 |ry map using the|
000020b0 0d 6d 6f 73 74 20 73 69 67 6e 69 66 69 63 61 6e |.most significan|
000020c0 74 20 62 69 74 20 6f 66 20 74 68 65 20 70 61 67 |t bit of the pag|
000020d0 65 64 20 72 6f 6d 20 73 65 6c 65 63 74 20 72 65 |ed rom select re|
000020e0 67 69 73 74 65 72 20 61 74 20 26 46 45 33 30 2e |gister at &FE30.|
000020f0 0d 53 65 74 74 69 6e 67 20 74 68 65 20 6d 6f 73 |.Setting the mos|
00002100 74 20 73 69 67 6e 69 66 69 63 61 6e 74 20 62 69 |t significant bi|
00002110 74 20 6f 66 20 74 68 65 20 70 61 67 65 64 20 72 |t of the paged r|
00002120 6f 6d 20 73 65 6c 65 63 74 20 72 65 67 69 73 74 |om select regist|
00002130 65 72 20 68 61 73 0d 6e 6f 20 65 66 66 65 63 74 |er has.no effect|
00002140 20 6f 6e 20 74 68 65 20 42 42 43 20 42 20 62 75 | on the BBC B bu|
00002150 74 20 6f 6e 20 74 68 65 20 42 42 43 20 42 2b 20 |t on the BBC B+ |
00002160 69 74 20 73 77 69 74 63 68 65 73 20 74 68 65 20 |it switches the |
00002170 70 61 67 65 64 20 6d 65 6d 6f 72 79 0d 66 72 6f |paged memory.fro|
00002180 6d 20 26 38 30 30 30 20 74 6f 20 26 41 46 46 46 |m &8000 to &AFFF|
00002190 20 69 6e 74 6f 20 74 68 65 20 6d 61 69 6e 20 6d | into the main m|
000021a0 65 6d 6f 72 79 20 6d 61 70 2e 20 42 42 43 20 54 |emory map. BBC T|
000021b0 65 6c 65 73 6f 66 74 77 61 72 65 20 68 61 73 0d |elesoftware has.|
000021c0 62 72 6f 61 64 63 61 73 74 20 61 20 70 72 6f 67 |broadcast a prog|
000021d0 72 61 6d 20 74 68 61 74 20 75 73 65 73 20 74 68 |ram that uses th|
000021e0 69 73 20 74 65 63 68 6e 69 71 75 65 20 74 6f 20 |is technique to |
000021f0 61 6c 6c 6f 77 20 42 42 43 20 42 2b 20 36 34 6b |allow BBC B+ 64k|
00002200 0d 63 6f 6d 70 75 74 65 72 20 75 73 65 72 73 20 |.computer users |
00002210 74 6f 20 6c 6f 61 64 20 61 6e 64 20 72 75 6e 20 |to load and run |
00002220 38 6b 20 73 65 72 76 69 63 65 20 72 6f 6d 73 20 |8k service roms |
00002230 69 6e 20 74 68 69 73 20 61 72 65 61 20 6f 66 20 |in this area of |
00002240 70 61 67 65 64 0d 6d 65 6d 6f 72 79 2e 0d 0d 20 |paged.memory... |
00002250 20 54 68 65 20 4d 61 73 74 65 72 20 63 6f 6d 70 | The Master comp|
00002260 75 74 65 72 20 75 73 65 73 20 61 20 73 6c 69 67 |uter uses a slig|
00002270 68 74 6c 79 20 64 69 66 66 65 72 65 6e 74 20 6d |htly different m|
00002280 65 6d 6f 72 79 20 6d 61 70 20 74 6f 20 74 68 65 |emory map to the|
00002290 20 42 0d 73 65 72 69 65 73 2e 20 54 68 65 20 22 | B.series. The "|
000022a0 73 70 61 72 65 22 20 31 32 6b 20 6f 66 20 70 61 |spare" 12k of pa|
000022b0 67 65 64 20 6d 65 6d 6f 72 79 20 68 61 73 20 6e |ged memory has n|
000022c0 6f 77 20 62 65 65 6e 20 73 70 6c 69 74 20 69 6e |ow been split in|
000022d0 74 6f 20 74 77 6f 0d 61 72 65 61 73 2c 20 6f 6e |to two.areas, on|
000022e0 65 20 66 72 6f 6d 20 26 38 30 30 30 20 74 6f 20 |e from &8000 to |
000022f0 26 38 46 46 46 20 61 6e 64 20 74 68 65 20 6f 74 |&8FFF and the ot|
00002300 68 65 72 20 66 72 6f 6d 20 26 43 30 30 30 20 74 |her from &C000 t|
00002310 6f 20 26 44 46 46 46 2e 20 54 68 65 0d 70 61 67 |o &DFFF. The.pag|
00002320 65 64 20 72 61 6d 20 66 72 6f 6d 20 26 38 30 30 |ed ram from &800|
00002330 30 20 74 6f 20 26 38 46 46 46 20 69 73 20 75 73 |0 to &8FFF is us|
00002340 65 64 20 62 79 20 74 68 65 20 4d 4f 53 20 61 73 |ed by the MOS as|
00002350 20 61 20 73 6f 66 74 20 6b 65 79 20 62 75 66 66 | a soft key buff|
00002360 65 72 2c 0d 63 68 61 72 61 63 74 65 72 20 66 6f |er,.character fo|
00002370 6e 74 2c 20 61 6e 64 20 56 44 55 20 77 6f 72 6b |nt, and VDU work|
00002380 73 70 61 63 65 2e 20 54 68 65 20 70 61 67 65 64 |space. The paged|
00002390 20 72 61 6d 20 66 72 6f 6d 20 26 43 30 30 30 20 | ram from &C000 |
000023a0 74 6f 20 26 44 43 46 46 0d 69 73 20 61 76 61 69 |to &DCFF.is avai|
000023b0 6c 61 62 6c 65 20 61 73 20 70 61 67 65 64 20 72 |lable as paged r|
000023c0 6f 6d 20 77 6f 72 6b 73 70 61 63 65 20 61 6e 64 |om workspace and|
000023d0 20 74 68 65 20 70 61 67 65 64 20 72 61 6d 20 66 | the paged ram f|
000023e0 72 6f 6d 20 26 44 44 30 30 20 74 6f 0d 26 44 46 |rom &DD00 to.&DF|
000023f0 46 46 20 69 73 20 75 73 65 64 20 61 73 20 4d 4f |FF is used as MO|
00002400 53 20 77 6f 72 6b 73 70 61 63 65 2e 0d 0d 0d 0d |S workspace.....|
00002410 0d 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 |. |
00002420 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 26 | &|
00002430 46 46 46 46 20 2b 2d 2d 2d 2d 2d 2d 2d 2b 20 26 |FFFF +-------+ &|
00002440 46 46 46 46 0d 20 20 20 20 20 20 20 20 20 20 20 |FFFF. |
00002450 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | |
00002460 20 20 20 20 20 20 20 20 20 21 20 20 20 20 20 20 | ! |
00002470 20 21 20 20 0d 20 20 20 20 20 20 20 20 20 20 20 | ! . |
00002480 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | |
00002490 20 20 20 20 20 20 20 20 20 21 20 20 4d 4f 53 20 | ! MOS |
000024a0 20 2b 2d 2d 2d 2d 2d 2d 2d 2b 20 26 44 46 46 46 | +-------+ &DFFF|
000024b0 0d 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 |. |
000024c0 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | |
000024d0 20 20 20 20 20 21 20 20 20 20 20 20 20 21 57 6b | ! !Wk|
000024e0 73 70 61 63 65 21 20 0d 20 20 20 20 26 42 46 46 |space! . &BFF|
000024f0 46 20 2d 2d 2b 2d 2d 2d 2d 2d 2d 2d 2b 2d 2d 2d |F --+-------+---|
00002500 2d 2d 2d 2d 2b 2d 2d 2d 2d 2d 2d 2d 2b 2d 2d 2d |----+-------+---|
00002510 2d 2d 2d 2d 2b 2d 2d 2d 2d 2d 2d 2d 2b 20 26 43 |----+-------+ &C|
00002520 30 30 30 0d 20 20 20 20 20 20 20 20 20 20 20 20 |000. |
00002530 21 20 52 4f 4d 20 26 43 21 20 52 4f 4d 20 26 44 |! ROM &C! ROM &D|
00002540 21 20 52 4f 4d 20 26 45 21 20 52 4f 4d 20 26 46 |! ROM &E! ROM &F|
00002550 21 0d 20 20 20 20 20 20 20 20 20 20 20 20 21 20 |!. ! |
00002560 20 20 20 20 20 20 21 20 20 20 20 20 20 20 21 20 | ! ! |
00002570 20 20 20 20 20 20 21 20 20 20 20 20 20 20 21 0d | ! !.|
00002580 20 20 20 20 20 20 20 20 20 20 20 20 21 20 42 41 | ! BA|
00002590 53 49 43 20 21 20 41 44 46 53 20 20 21 20 56 69 |SIC ! ADFS ! Vi|
000025a0 65 77 20 20 21 20 54 65 72 6d 2e 20 2b 2d 2d 2d |ew ! Term. +---|
000025b0 2d 2d 2d 2d 2b 20 26 38 46 46 46 0d 20 20 20 20 |----+ &8FFF. |
000025c0 26 38 30 30 30 20 2d 2d 2b 2d 2d 2d 2d 2d 2d 2d |&8000 --+-------|
000025d0 2b 2d 2d 2d 2d 2d 2d 2d 2b 2d 2d 2d 2d 2d 2d 2d |+-------+-------|
*
000025f0 2b 20 26 38 30 30 30 0d 20 20 20 20 55 70 20 74 |+ &8000. Up t|
00002600 6f 20 31 36 20 53 69 64 65 77 61 79 73 20 72 6f |o 16 Sideways ro|
00002610 6d 2f 72 61 6d 20 62 61 6e 6b 73 20 21 20 20 20 |m/ram banks ! |
00002620 20 20 20 20 21 20 20 20 20 20 20 20 21 0d 20 20 | ! !. |
00002630 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | |
*
00002650 20 20 21 20 20 55 73 65 72 20 21 20 53 68 61 64 | ! User ! Shad|
00002660 6f 77 21 0d 20 20 20 20 20 20 20 20 20 20 20 20 |ow!. |
00002670 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | |
00002680 20 20 20 20 20 20 20 20 21 20 6d 65 6d 6f 72 79 | ! memory|
00002690 21 20 20 72 61 6d 20 20 21 0d 20 20 20 20 20 20 |! ram !. |
000026a0 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | |
000026b0 20 20 20 20 20 20 20 20 20 20 20 20 20 20 21 20 | ! |
000026c0 20 20 20 20 20 20 21 20 20 20 20 20 20 20 21 0d | ! !.|
000026d0 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | |
*
000026f0 20 20 20 20 21 20 20 20 20 20 20 20 2b 2d 2d 2d | ! +---|
00002700 2d 2d 2d 2d 2b 20 26 33 30 30 30 0d 20 20 20 20 |----+ &3000. |
00002710 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | |
*
00002730 21 20 20 20 20 20 20 20 21 0d 20 20 20 20 20 20 |! !. |
00002740 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | |
00002750 20 20 20 20 20 20 20 20 26 30 45 30 30 20 2b 2d | &0E00 +-|
00002760 2d 2d 2d 2d 2d 2d 2b 20 4f 73 68 77 6d 20 0d 20 |------+ Oshwm . |
00002770 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 | |
00002780 20 20 20 20 20 20 20 20 20 20 20 20 20 26 30 30 | &00|
00002790 30 30 20 2b 2d 2d 2d 2d 2d 2d 2d 2b 20 26 30 30 |00 +-------+ &00|
000027a0 30 30 0d 0d 46 69 67 75 72 65 20 31 2e 33 20 4d |00..Figure 1.3 M|
000027b0 65 6d 6f 72 79 20 6d 61 70 20 6f 66 20 74 68 65 |emory map of the|
000027c0 20 42 42 43 20 4d 61 73 74 65 72 0d 2d 2d 2d 2d | BBC Master.----|
000027d0 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d |----------------|
*
000027f0 2d 2d 2d 0d 0d 0d 20 20 50 61 67 65 64 20 72 6f |---... Paged ro|
00002800 6d 20 77 6f 72 6b 73 70 61 63 65 20 6f 6e 20 74 |m workspace on t|
00002810 68 65 20 42 42 43 20 42 20 61 6e 64 20 42 2b 20 |he BBC B and B+ |
00002820 69 73 20 6a 75 73 74 20 62 65 6c 6f 77 20 74 68 |is just below th|
00002830 65 20 75 73 65 72 0d 6d 65 6d 6f 72 79 2e 20 54 |e user.memory. T|
00002840 68 65 20 42 42 43 20 42 20 44 46 53 20 63 6c 61 |he BBC B DFS cla|
00002850 69 6d 73 20 32 2e 37 35 6b 20 6f 66 20 77 6f 72 |ims 2.75k of wor|
00002860 6b 73 70 61 63 65 20 66 72 6f 6d 20 26 30 45 30 |kspace from &0E0|
00002870 30 20 74 6f 20 26 31 39 30 30 2e 0d 54 68 69 73 |0 to &1900..This|
00002880 20 77 6f 72 6b 73 70 61 63 65 20 63 61 6e 20 62 | workspace can b|
00002890 65 20 69 6e 20 70 61 67 65 64 20 6d 65 6d 6f 72 |e in paged memor|
000028a0 79 20 6f 6e 20 74 68 65 20 4d 61 73 74 65 72 20 |y on the Master |
000028b0 73 65 72 69 65 73 20 61 6c 6c 6f 77 69 6e 67 0d |series allowing.|
000028c0 4f 73 68 77 6d 20 74 6f 20 73 74 61 79 20 61 74 |Oshwm to stay at|
000028d0 20 26 30 45 30 30 20 77 69 74 68 20 61 6c 6c 20 | &0E00 with all |
000028e0 66 69 6c 69 6e 67 20 73 79 73 74 65 6d 73 2e 20 |filing systems. |
000028f0 42 69 74 20 33 20 6f 66 20 74 68 65 20 70 61 67 |Bit 3 of the pag|
00002900 65 64 0d 6d 65 6d 6f 72 79 20 73 65 6c 65 63 74 |ed.memory select|
00002910 20 72 65 67 69 73 74 65 72 20 61 74 20 26 46 45 | register at &FE|
00002920 33 34 20 69 73 20 75 73 65 64 20 74 6f 20 6f 76 |34 is used to ov|
00002930 65 72 6c 61 79 20 74 68 65 20 70 61 67 65 64 20 |erlay the paged |
00002940 72 6f 6d 0d 77 6f 72 6b 73 70 61 63 65 20 6f 6e |rom.workspace on|
00002950 74 6f 20 74 68 65 20 4d 61 73 74 65 72 20 4d 4f |to the Master MO|
00002960 53 20 73 6f 20 74 68 61 74 20 69 74 20 61 70 70 |S so that it app|
00002970 65 61 72 73 20 61 62 6f 76 65 20 74 68 65 20 70 |ears above the p|
00002980 61 67 65 64 20 72 6f 6d 0d 75 73 69 6e 67 20 69 |aged rom.using i|
00002990 74 2e 20 42 69 74 20 33 20 6f 66 20 74 68 65 20 |t. Bit 3 of the |
000029a0 70 61 67 65 64 20 6d 65 6d 6f 72 79 20 73 65 6c |paged memory sel|
000029b0 65 63 74 20 72 65 67 69 73 74 65 72 20 63 61 6e |ect register can|
000029c0 20 62 65 20 74 6f 67 67 6c 65 64 0d 64 69 72 65 | be toggled.dire|
000029d0 63 74 6c 79 20 62 75 74 20 79 6f 75 20 6d 75 73 |ctly but you mus|
000029e0 74 20 6e 6f 74 20 64 69 72 65 63 74 6c 79 20 61 |t not directly a|
000029f0 6c 74 65 72 20 61 6e 79 20 6f 74 68 65 72 20 62 |lter any other b|
00002a00 69 74 20 69 6e 20 74 68 69 73 0d 72 65 67 69 73 |it in this.regis|
00002a10 74 65 72 2e 20 54 68 69 73 20 74 6f 70 69 63 20 |ter. This topic |
00002a20 77 69 6c 6c 20 62 65 20 63 6f 76 65 72 65 64 20 |will be covered |
00002a30 69 6e 20 6d 6f 72 65 20 64 65 74 61 69 6c 20 69 |in more detail i|
00002a40 6e 20 6d 6f 64 75 6c 65 73 20 31 31 20 61 6e 64 |n modules 11 and|
00002a50 0d 31 32 20 77 68 69 63 68 20 64 65 61 6c 20 77 |.12 which deal w|
00002a60 69 74 68 20 70 61 67 65 64 20 72 6f 6d 20 77 6f |ith paged rom wo|
00002a70 72 6b 73 70 61 63 65 2e 0d 0d 20 20 54 68 65 20 |rkspace... The |
00002a80 75 73 65 20 6f 66 20 74 68 65 20 6c 65 61 73 74 |use of the least|
00002a90 20 73 69 67 6e 69 66 69 63 61 6e 74 20 6e 79 62 | significant nyb|
00002aa0 62 6c 65 20 6f 66 20 74 68 65 20 70 61 67 65 64 |ble of the paged|
00002ab0 20 72 6f 6d 20 73 65 6c 65 63 74 0d 72 65 67 69 | rom select.regi|
00002ac0 73 74 65 72 20 61 74 20 69 73 20 63 6f 6d 6d 6f |ster at is commo|
00002ad0 6e 20 74 6f 20 61 6c 6c 20 42 42 43 20 6d 69 63 |n to all BBC mic|
00002ae0 72 6f 73 2e 20 54 68 65 20 6f 70 65 72 61 74 69 |ros. The operati|
00002af0 6e 67 20 73 79 73 74 65 6d 20 75 73 65 73 0d 74 |ng system uses.t|
00002b00 68 69 73 20 72 65 67 69 73 74 65 72 2c 20 61 6e |his register, an|
00002b10 64 20 74 68 65 20 7a 65 72 6f 20 70 61 67 65 20 |d the zero page |
00002b20 63 6f 70 79 20 6f 66 20 69 74 20 61 74 20 26 46 |copy of it at &F|
00002b30 34 2c 20 74 6f 20 6b 65 65 70 20 74 72 61 63 6b |4, to keep track|
00002b40 20 6f 66 0d 77 68 69 63 68 20 70 61 67 65 64 20 | of.which paged |
00002b50 72 6f 6d 20 69 73 20 62 65 69 6e 67 20 75 73 65 |rom is being use|
00002b60 64 20 61 74 20 61 6e 79 20 74 69 6d 65 2e 20 49 |d at any time. I|
00002b70 66 20 79 6f 75 20 77 61 6e 74 20 74 6f 20 61 6c |f you want to al|
00002b80 74 65 72 20 74 68 69 73 0d 72 65 67 69 73 74 65 |ter this.registe|
00002b90 72 20 64 69 72 65 63 74 6c 79 20 79 6f 75 20 63 |r directly you c|
00002ba0 61 6e 20 6f 6e 6c 79 20 64 6f 20 73 6f 20 66 72 |an only do so fr|
00002bb0 6f 6d 20 6d 61 63 68 69 6e 65 20 63 6f 64 65 2e |om machine code.|
00002bc0 20 49 66 20 79 6f 75 20 61 6c 74 65 72 0d 69 74 | If you alter.it|
00002bd0 20 66 72 6f 6d 20 42 41 53 49 43 20 6f 72 20 61 | from BASIC or a|
00002be0 6e 79 20 6f 74 68 65 72 20 6c 61 6e 67 75 61 67 |ny other languag|
00002bf0 65 20 72 6f 6d 20 79 6f 75 20 77 69 6c 6c 20 63 |e rom you will c|
00002c00 61 75 73 65 20 74 68 65 20 63 6f 6d 70 75 74 65 |ause the compute|
00002c10 72 20 74 6f 0d 68 61 6e 67 20 75 70 2e 0d 0d 20 |r to.hang up... |
00002c20 20 54 68 65 20 6f 72 64 65 72 20 69 6e 20 77 68 | The order in wh|
00002c30 69 63 68 20 74 68 65 20 70 61 67 65 64 20 72 6f |ich the paged ro|
00002c40 6d 20 73 65 6c 65 63 74 20 72 65 67 69 73 74 65 |m select registe|
00002c50 72 20 61 6e 64 20 69 74 73 20 63 6f 70 79 20 61 |r and its copy a|
00002c60 74 20 26 46 34 0d 61 72 65 20 61 6c 74 65 72 65 |t &F4.are altere|
00002c70 64 20 69 73 20 69 6d 70 6f 72 74 61 6e 74 2e 20 |d is important. |
00002c80 59 6f 75 20 6d 75 73 74 20 73 74 6f 72 65 20 74 |You must store t|
00002c90 68 65 20 73 61 6d 65 20 6e 75 6d 62 65 72 20 69 |he same number i|
00002ca0 6e 20 62 6f 74 68 0d 6c 6f 63 61 74 69 6f 6e 73 |n both.locations|
00002cb0 20 61 6e 64 20 61 6c 74 65 72 20 26 46 34 20 66 | and alter &F4 f|
00002cc0 69 72 73 74 2e 20 49 6d 6d 65 64 69 61 74 6c 79 |irst. Immediatly|
00002cd0 20 61 66 74 65 72 20 61 6c 74 65 72 69 6e 67 20 | after altering |
00002ce0 26 46 34 20 79 6f 75 20 6d 75 73 74 0d 73 74 6f |&F4 you must.sto|
00002cf0 72 65 20 74 68 65 20 73 61 6d 65 20 76 61 6c 75 |re the same valu|
00002d00 65 20 69 6e 20 26 46 45 33 30 2e 20 46 6f 72 20 |e in &FE30. For |
00002d10 65 78 61 6d 70 6c 65 3a 0d 0d 20 20 4c 44 41 20 |example:.. LDA |
00002d20 23 26 30 41 0d 20 20 53 54 41 20 26 46 34 0d 20 |#&0A. STA &F4. |
00002d30 20 53 54 41 20 26 46 45 33 30 0d 0d 20 20 54 68 | STA &FE30.. Th|
00002d40 69 73 20 63 6f 64 65 20 77 69 6c 6c 20 73 77 69 |is code will swi|
00002d50 74 63 68 20 62 61 6e 6b 20 26 30 41 20 69 6e 74 |tch bank &0A int|
00002d60 6f 20 74 68 65 20 6d 61 69 6e 20 6d 65 6d 6f 72 |o the main memor|
00002d70 79 20 6d 61 70 2e 20 49 66 20 79 6f 75 0d 72 65 |y map. If you.re|
00002d80 76 65 72 73 65 20 74 68 65 20 6f 72 64 65 72 20 |verse the order |
00002d90 6f 66 20 74 68 65 20 6c 61 73 74 20 74 77 6f 20 |of the last two |
00002da0 69 6e 73 74 72 75 63 74 69 6f 6e 73 20 79 6f 75 |instructions you|
00002db0 20 77 69 6c 6c 20 66 69 6e 64 20 74 68 61 74 20 | will find that |
00002dc0 39 39 25 0d 6f 66 20 74 68 65 20 74 69 6d 65 20 |99%.of the time |
00002dd0 65 76 65 72 79 74 68 69 6e 67 20 77 6f 72 6b 73 |everything works|
00002de0 20 70 72 6f 70 65 72 6c 79 20 62 75 74 2c 20 73 | properly but, s|
00002df0 6f 6f 6e 65 72 20 6f 72 20 6c 61 74 65 72 2c 20 |ooner or later, |
00002e00 61 6e 0d 69 6e 74 65 72 75 70 74 20 6f 63 63 75 |an.interupt occu|
00002e10 72 69 6e 67 20 62 65 74 77 65 65 6e 20 74 68 65 |ring between the|
00002e20 20 74 77 6f 20 73 74 6f 72 65 20 69 6e 73 74 72 | two store instr|
00002e30 75 63 74 69 6f 6e 73 20 77 69 6c 6c 20 63 61 75 |uctions will cau|
00002e40 73 65 20 74 6f 0d 63 6f 6d 70 75 74 65 72 20 74 |se to.computer t|
00002e50 6f 20 68 61 6e 67 20 75 70 2e 20 53 77 69 74 63 |o hang up. Switc|
00002e60 68 69 6e 67 20 61 20 70 61 67 65 64 20 72 6f 6d |hing a paged rom|
00002e70 20 69 6e 74 6f 20 74 68 65 20 6d 61 69 6e 20 6d | into the main m|
00002e80 65 6d 6f 72 79 20 6d 61 70 20 69 6e 0d 74 68 69 |emory map in.thi|
00002e90 73 20 77 61 79 20 63 61 6e 20 62 65 20 71 75 69 |s way can be qui|
00002ea0 74 65 20 75 73 65 66 75 6c 20 69 66 20 79 6f 75 |te useful if you|
00002eb0 20 77 61 6e 74 20 74 6f 20 74 72 61 6e 73 66 65 | want to transfe|
00002ec0 72 20 74 68 65 20 63 6f 6e 74 65 6e 74 73 20 6f |r the contents o|
00002ed0 66 20 61 0d 72 6f 6d 20 69 6e 74 6f 20 75 73 65 |f a.rom into use|
00002ee0 72 20 6d 65 6d 6f 72 79 20 6f 72 20 74 72 61 6e |r memory or tran|
00002ef0 73 66 65 72 20 74 68 65 20 63 6f 6e 74 65 6e 74 |sfer the content|
00002f00 73 20 6f 66 20 75 73 65 72 20 6d 65 6d 6f 72 79 |s of user memory|
00002f10 20 69 6e 74 6f 20 61 0d 70 61 72 74 69 63 75 6c | into a.particul|
00002f20 61 72 20 73 69 64 65 77 61 79 73 20 72 61 6d 2e |ar sideways ram.|
00002f30 0d 0d 20 20 54 68 65 72 65 20 69 73 20 61 6e 20 |.. There is an |
00002f40 6f 66 66 69 63 69 61 6c 20 77 61 79 20 74 6f 20 |official way to |
00002f50 72 65 61 64 20 61 20 62 79 74 65 20 6f 66 20 6d |read a byte of m|
00002f60 65 6d 6f 72 79 20 66 72 6f 6d 20 61 6e 79 20 70 |emory from any p|
00002f70 61 67 65 64 0d 72 6f 6d 2e 20 54 68 69 73 20 75 |aged.rom. This u|
00002f80 73 65 73 20 74 68 65 20 6f 70 65 72 61 74 69 6e |ses the operatin|
00002f90 67 20 73 79 73 74 65 6d 20 63 61 6c 6c 20 4f 73 |g system call Os|
00002fa0 72 64 72 6d 20 61 74 20 26 46 46 42 39 20 77 69 |rdrm at &FFB9 wi|
00002fb0 74 68 20 74 68 65 0d 72 65 6c 65 76 61 6e 74 20 |th the.relevant |
00002fc0 70 61 67 65 64 20 72 6f 6d 20 6e 75 6d 62 65 72 |paged rom number|
00002fd0 20 69 6e 20 74 68 65 20 59 20 72 65 67 69 73 74 | in the Y regist|
00002fe0 65 72 20 61 6e 64 20 74 68 65 20 61 64 64 72 65 |er and the addre|
00002ff0 73 73 20 6f 66 20 74 68 65 0d 62 79 74 65 20 69 |ss of the.byte i|
00003000 6e 20 74 68 65 20 70 61 67 65 64 20 72 6f 6d 20 |n the paged rom |
00003010 69 6e 20 6c 6f 63 61 74 69 6f 6e 73 20 26 46 36 |in locations &F6|
00003020 20 61 6e 64 20 26 46 37 20 28 74 68 65 20 70 61 | and &F7 (the pa|
00003030 67 65 64 20 72 6f 6d 0d 70 6f 69 6e 74 65 72 73 |ged rom.pointers|
00003040 29 2e 20 54 68 65 20 76 61 6c 75 65 20 6f 66 20 |). The value of |
00003050 74 68 65 20 62 79 74 65 20 72 65 61 64 20 62 79 |the byte read by|
00003060 20 4f 73 72 64 72 6d 20 69 73 20 72 65 74 75 72 | Osrdrm is retur|
00003070 6e 65 64 20 69 6e 20 74 68 65 0d 61 63 63 75 6d |ned in the.accum|
00003080 75 6c 61 74 6f 72 2e 20 54 68 65 20 58 2c 20 59 |ulator. The X, Y|
00003090 20 61 6e 64 20 73 74 61 74 75 73 20 72 65 67 69 | and status regi|
000030a0 73 74 65 72 73 20 77 69 6c 6c 20 62 65 20 75 6e |sters will be un|
000030b0 64 65 66 69 6e 65 64 20 61 66 74 65 72 20 74 68 |defined after th|
000030c0 65 0d 63 61 6c 6c 2e 0d 0d 20 20 42 6f 74 68 20 |e.call... Both |
000030d0 74 68 65 73 65 20 74 65 63 68 6e 69 71 75 65 73 |these techniques|
000030e0 20 61 72 65 20 64 65 6d 6f 6e 73 74 72 61 74 65 | are demonstrate|
000030f0 64 20 69 6e 20 74 68 65 20 70 72 6f 67 72 61 6d |d in the program|
00003100 20 52 45 41 44 52 4f 4d 2e 20 57 68 65 6e 0d 74 | READROM. When.t|
00003110 68 65 20 70 72 6f 67 72 61 6d 20 69 73 20 72 75 |he program is ru|
00003120 6e 6e 69 6e 67 20 69 74 20 75 73 65 73 20 4f 73 |nning it uses Os|
00003130 72 64 72 6d 20 74 6f 20 72 65 61 64 20 74 68 65 |rdrm to read the|
00003140 20 74 69 74 6c 65 20 73 74 72 69 6e 67 20 69 6e | title string in|
00003150 0d 65 76 65 72 79 20 72 6f 6d 20 73 6f 63 6b 65 |.every rom socke|
00003160 74 20 74 68 61 74 20 68 61 73 20 61 6e 20 61 63 |t that has an ac|
00003170 74 69 76 65 20 72 6f 6d 20 69 6d 61 67 65 20 61 |tive rom image a|
00003180 6e 64 20 74 68 65 6e 20 70 72 6f 6d 70 74 73 20 |nd then prompts |
00003190 74 68 65 0d 75 73 65 72 20 74 6f 20 63 68 6f 6f |the.user to choo|
000031a0 73 65 20 77 68 69 63 68 20 72 6f 6d 20 6e 75 6d |se which rom num|
000031b0 62 65 72 2c 20 66 72 6f 6d 20 30 2d 31 35 2c 20 |ber, from 0-15, |
000031c0 74 6f 20 73 77 69 74 63 68 20 69 6e 74 6f 20 74 |to switch into t|
000031d0 68 65 20 6d 61 69 6e 0d 6d 65 6d 6f 72 79 20 6d |he main.memory m|
000031e0 61 70 2e 20 54 68 65 20 63 68 6f 73 65 6e 20 72 |ap. The chosen r|
000031f0 6f 6d 20 69 73 20 73 77 69 74 63 68 65 64 20 69 |om is switched i|
00003200 6e 20 61 6e 64 20 63 6f 70 69 65 64 20 66 72 6f |n and copied fro|
00003210 6d 20 26 38 30 30 30 20 74 6f 0d 26 33 43 30 30 |m &8000 to.&3C00|
00003220 20 61 6e 64 20 74 68 65 6e 20 73 77 69 74 63 68 | and then switch|
00003230 65 64 20 62 61 63 6b 20 6f 75 74 20 61 67 61 69 |ed back out agai|
00003240 6e 2e 20 54 68 65 20 72 6f 6d 20 69 6d 61 67 65 |n. The rom image|
00003250 20 63 61 6e 20 74 68 65 6e 20 62 65 0d 65 78 61 | can then be.exa|
00003260 6d 69 6e 65 64 20 61 6e 64 2c 20 69 66 20 72 65 |mined and, if re|
00003270 71 75 69 72 65 64 2c 20 73 61 76 65 64 20 74 6f |quired, saved to|
00003280 20 74 68 65 20 63 75 72 72 65 6e 74 6c 79 20 61 | the currently a|
00003290 63 74 69 76 65 20 66 69 6c 69 6e 67 0d 73 79 73 |ctive filing.sys|
000032a0 74 65 6d 2e 20 41 6c 74 68 6f 75 67 68 20 73 6f |tem. Although so|
000032b0 6d 65 20 6f 66 20 74 68 65 20 70 72 6f 67 72 61 |me of the progra|
000032c0 6d 20 69 73 20 69 6e 20 42 41 53 49 43 20 74 68 |m is in BASIC th|
000032d0 65 20 73 77 69 74 63 68 69 6e 67 20 61 6e 64 0d |e switching and.|
000032e0 63 6f 70 79 69 6e 67 20 63 61 6e 20 6f 6e 6c 79 |copying can only|
000032f0 20 62 65 20 64 6f 6e 65 20 69 6e 20 6d 61 63 68 | be done in mach|
00003300 69 6e 65 20 63 6f 64 65 2e 0d 0d 20 20 54 68 65 |ine code... The|
00003310 20 70 72 6f 67 72 61 6d 20 75 73 65 73 20 4f 73 | program uses Os|
00003320 62 79 74 65 20 26 41 41 20 74 6f 20 66 69 6e 64 |byte &AA to find|
00003330 20 74 68 65 20 73 74 61 72 74 20 6f 66 20 74 68 | the start of th|
00003340 65 20 72 6f 6d 20 69 6e 66 6f 72 6d 61 74 69 6f |e rom informatio|
00003350 6e 0d 74 61 62 6c 65 2e 20 54 68 69 73 20 63 61 |n.table. This ca|
00003360 6c 6c 20 72 65 74 75 72 6e 73 20 74 68 65 20 6f |ll returns the o|
00003370 72 69 67 69 6e 20 6f 66 20 61 20 31 36 20 62 79 |rigin of a 16 by|
00003380 74 65 20 74 61 62 6c 65 20 63 6f 6e 74 61 69 6e |te table contain|
00003390 69 6e 67 20 6f 6e 65 0d 62 79 74 65 20 70 65 72 |ing one.byte per|
000033a0 20 70 61 67 65 64 20 72 6f 6d 2e 20 45 61 63 68 | paged rom. Each|
000033b0 20 62 79 74 65 20 63 6f 6e 74 61 69 6e 73 20 74 | byte contains t|
000033c0 68 65 20 72 6f 6d 20 74 79 70 65 20 62 79 74 65 |he rom type byte|
000033d0 20 63 6f 6e 74 61 69 6e 65 64 20 69 6e 0d 6c 6f | contained in.lo|
000033e0 63 61 74 69 6f 6e 20 26 38 30 30 36 20 6f 66 20 |cation &8006 of |
000033f0 74 68 65 20 72 6f 6d 20 6f 72 20 63 6f 6e 74 61 |the rom or conta|
00003400 69 6e 73 20 7a 65 72 6f 20 69 66 20 61 6e 20 61 |ins zero if an a|
00003410 63 74 69 76 65 20 72 6f 6d 20 69 73 20 6e 6f 74 |ctive rom is not|
00003420 0d 70 72 65 73 65 6e 74 2e 20 52 6f 6d 20 74 79 |.present. Rom ty|
00003430 70 65 20 62 79 74 65 73 20 61 72 65 20 61 6e 20 |pe bytes are an |
00003440 69 6d 70 6f 72 74 61 6e 74 20 70 61 72 74 20 6f |important part o|
00003450 66 20 74 68 65 20 72 6f 6d 20 68 65 61 64 65 72 |f the rom header|
00003460 20 61 6e 64 0d 77 69 6c 6c 20 62 65 20 64 65 61 | and.will be dea|
00003470 6c 74 20 77 69 74 68 20 69 6e 20 6d 6f 72 65 20 |lt with in more |
00003480 64 65 74 61 69 6c 20 77 68 65 6e 20 72 6f 6d 20 |detail when rom |
00003490 68 65 61 64 65 72 73 20 61 72 65 20 63 6f 6e 73 |headers are cons|
000034a0 69 64 65 72 65 64 20 69 6e 0d 6d 6f 64 75 6c 65 |idered in.module|
000034b0 20 32 2e 0d 0d 20 20 43 68 61 69 6e 20 74 68 65 | 2... Chain the|
000034c0 20 70 72 6f 67 72 61 6d 20 52 45 41 44 52 4f 4d | program READROM|
000034d0 20 61 6e 64 20 73 61 74 69 73 66 79 20 79 6f 75 | and satisfy you|
000034e0 72 73 65 6c 66 20 74 68 61 74 20 69 74 20 77 6f |rself that it wo|
000034f0 72 6b 73 0d 70 72 6f 70 65 72 6c 79 2e 20 49 74 |rks.properly. It|
00003500 20 6d 75 73 74 20 72 75 6e 20 69 6e 20 74 68 65 | must run in the|
00003510 20 49 2f 4f 20 70 72 6f 63 65 73 73 6f 72 20 61 | I/O processor a|
00003520 6e 64 20 77 69 6c 6c 20 6e 6f 74 20 77 6f 72 6b |nd will not work|
00003530 20 69 6e 20 61 0d 73 65 63 6f 6e 64 20 70 72 6f | in a.second pro|
00003540 63 65 73 73 6f 72 2e 0d 0d 20 20 54 68 65 72 65 |cessor... There|
00003550 20 61 72 65 20 74 77 6f 20 6d 61 63 68 69 6e 65 | are two machine|
00003560 20 63 6f 64 65 20 72 6f 75 74 69 6e 65 73 20 75 | code routines u|
00003570 73 65 64 20 69 6e 20 74 68 65 20 70 72 6f 67 72 |sed in the progr|
00003580 61 6d 2e 20 54 68 65 20 66 69 72 73 74 0d 28 6c |am. The first.(l|
00003590 69 6e 65 73 20 32 30 30 2d 34 33 30 29 20 69 73 |ines 200-430) is|
000035a0 20 63 61 6c 6c 65 64 20 6f 6e 63 65 20 66 6f 72 | called once for|
000035b0 20 65 61 63 68 20 70 6f 73 73 69 62 6c 65 20 72 | each possible r|
000035c0 6f 6d 20 6e 75 6d 62 65 72 20 66 72 6f 6d 20 30 |om number from 0|
000035d0 20 74 6f 0d 31 35 2e 20 49 74 20 6c 6f 6f 6b 73 | to.15. It looks|
000035e0 20 75 70 20 74 68 65 20 61 64 64 72 65 73 73 20 | up the address |
000035f0 6f 66 20 74 68 65 20 73 74 61 72 74 20 6f 66 20 |of the start of |
00003600 74 68 65 20 72 6f 6d 20 69 6e 66 6f 72 6d 61 74 |the rom informat|
00003610 69 6f 6e 20 74 61 62 6c 65 0d 77 69 74 68 20 4f |ion table.with O|
00003620 73 62 79 74 65 20 26 41 41 20 28 6c 69 6e 65 73 |sbyte &AA (lines|
00003630 20 32 31 30 2d 32 34 30 29 20 61 6e 64 20 74 68 | 210-240) and th|
00003640 65 6e 20 75 73 65 73 20 74 68 65 20 6e 75 6d 62 |en uses the numb|
00003650 65 72 20 6f 66 20 74 68 65 20 72 6f 6d 20 61 73 |er of the rom as|
00003660 0d 61 6e 20 6f 66 66 73 65 74 20 69 6e 20 74 68 |.an offset in th|
00003670 65 20 59 20 72 65 67 69 73 74 65 72 20 74 6f 20 |e Y register to |
00003680 73 65 65 20 69 66 20 74 68 65 72 65 20 69 73 20 |see if there is |
00003690 61 20 76 61 6c 69 64 20 72 6f 6d 20 69 6e 20 74 |a valid rom in t|
000036a0 68 65 0d 73 6f 63 6b 65 74 20 62 65 69 6e 67 20 |he.socket being |
000036b0 63 6f 6e 73 69 64 65 72 65 64 20 28 6c 69 6e 65 |considered (line|
000036c0 20 32 38 30 29 2e 20 49 66 20 74 68 65 72 65 20 | 280). If there |
000036d0 69 73 20 61 20 76 61 6c 69 64 20 72 6f 6d 20 69 |is a valid rom i|
000036e0 6d 61 67 65 0d 70 72 65 73 65 6e 74 20 74 68 65 |mage.present the|
000036f0 20 72 6f 75 74 69 6e 65 20 72 65 61 64 73 20 74 | routine reads t|
00003700 68 65 20 74 69 74 6c 65 20 6f 66 20 74 68 65 20 |he title of the |
00003710 72 6f 6d 20 75 73 69 6e 67 20 4f 73 72 64 72 6d |rom using Osrdrm|
00003720 20 61 6e 64 0d 64 69 73 70 6c 61 79 73 20 69 74 | and.displays it|
00003730 20 6f 6e 20 74 68 65 20 73 63 72 65 65 6e 20 28 | on the screen (|
00003740 6c 69 6e 65 73 20 33 34 30 2d 34 33 30 29 2e 20 |lines 340-430). |
00003750 54 68 65 20 72 6f 6d 20 74 69 74 6c 65 20 61 6c |The rom title al|
00003760 77 61 79 73 20 73 74 61 72 74 73 0d 61 74 20 26 |ways starts.at &|
00003770 38 30 30 39 20 69 6e 20 61 20 76 61 6c 69 64 20 |8009 in a valid |
00003780 72 6f 6d 20 69 6d 61 67 65 20 61 6e 64 20 61 6c |rom image and al|
00003790 77 61 79 73 20 65 6e 64 73 20 77 69 74 68 20 61 |ways ends with a|
000037a0 20 62 69 6e 61 72 79 20 7a 65 72 6f 2e 0d 0d 20 | binary zero... |
000037b0 20 54 68 65 20 73 65 63 6f 6e 64 20 6d 61 63 68 | The second mach|
000037c0 69 6e 65 20 63 6f 64 65 20 72 6f 75 74 69 6e 65 |ine code routine|
000037d0 20 69 73 20 69 6e 20 6c 69 6e 65 73 20 34 34 30 | is in lines 440|
000037e0 2d 37 30 30 2e 20 54 68 69 73 20 73 74 6f 72 65 |-700. This store|
000037f0 73 20 74 68 65 0d 63 75 72 72 65 6e 74 20 72 6f |s the.current ro|
00003800 6d 20 6e 75 6d 62 65 72 20 28 6c 69 6e 65 73 20 |m number (lines |
00003810 34 35 30 2d 34 36 30 29 20 62 65 66 6f 72 65 20 |450-460) before |
00003820 73 77 69 74 63 68 69 6e 67 20 74 68 65 20 63 68 |switching the ch|
00003830 6f 73 65 6e 20 72 6f 6d 0d 69 6e 74 6f 20 74 68 |osen rom.into th|
00003840 65 20 6d 61 69 6e 20 6d 65 6d 6f 72 79 20 6d 61 |e main memory ma|
00003850 70 20 28 6c 69 6e 65 73 20 34 37 30 2d 34 39 30 |p (lines 470-490|
00003860 29 2e 20 49 74 20 74 68 65 6e 20 63 6f 70 69 65 |). It then copie|
00003870 73 20 74 68 65 20 63 68 6f 73 65 6e 0d 72 6f 6d |s the chosen.rom|
00003880 20 69 6d 61 67 65 20 69 6e 74 6f 20 75 73 65 72 | image into user|
00003890 20 6d 65 6d 6f 72 79 20 28 6c 69 6e 65 73 20 35 | memory (lines 5|
000038a0 30 30 2d 36 36 30 29 2c 20 61 6e 64 20 66 69 6e |00-660), and fin|
000038b0 61 6c 6c 79 20 73 77 69 74 63 68 65 73 20 74 68 |ally switches th|
000038c0 65 0d 6f 72 69 67 69 6e 61 6c 20 72 6f 6d 20 62 |e.original rom b|
000038d0 61 63 6b 20 69 6e 74 6f 20 74 68 65 20 6d 61 69 |ack into the mai|
000038e0 6e 20 6d 65 6d 6f 72 79 20 6d 61 70 20 28 6c 69 |n memory map (li|
000038f0 6e 65 73 20 36 37 30 2d 36 39 30 29 2e 0d 0d 20 |nes 670-690)... |
00003900 20 54 68 65 20 42 41 53 49 43 20 70 61 72 74 20 | The BASIC part |
00003910 6f 66 20 74 68 65 20 70 72 6f 67 72 61 6d 20 69 |of the program i|
00003920 73 20 6d 61 69 6e 6c 79 20 63 6f 6e 63 65 72 6e |s mainly concern|
00003930 65 64 20 77 69 74 68 20 64 69 73 70 6c 61 79 69 |ed with displayi|
00003940 6e 67 0d 74 68 65 20 63 6f 70 79 20 6f 66 20 74 |ng.the copy of t|
00003950 68 65 20 72 6f 6d 20 69 6d 61 67 65 20 6f 6e 20 |he rom image on |
00003960 74 68 65 20 73 63 72 65 65 6e 20 28 6c 69 6e 65 |the screen (line|
00003970 73 20 38 36 30 2d 39 39 30 29 20 61 6e 64 2c 20 |s 860-990) and, |
00003980 69 66 0d 72 65 71 75 69 72 65 64 2c 20 77 69 74 |if.required, wit|
00003990 68 20 73 61 76 69 6e 67 20 61 20 63 6f 70 79 20 |h saving a copy |
000039a0 6f 66 20 74 68 65 20 72 6f 6d 20 69 6d 61 67 65 |of the rom image|
000039b0 20 6f 6e 74 6f 20 64 69 73 63 20 6f 72 20 74 61 | onto disc or ta|
000039c0 70 65 0d 28 50 52 4f 43 73 61 76 65 2c 20 6c 69 |pe.(PROCsave, li|
000039d0 6e 65 73 20 31 30 30 30 2d 31 31 39 30 29 2e 20 |nes 1000-1190). |
000039e0 42 65 66 6f 72 65 20 69 74 20 6d 61 6b 65 73 20 |Before it makes |
000039f0 61 20 63 6f 70 79 20 6f 66 20 74 68 65 20 72 6f |a copy of the ro|
00003a00 6d 20 69 6d 61 67 65 0d 6f 6e 74 6f 20 64 69 73 |m image.onto dis|
00003a10 63 20 74 68 65 20 70 72 6f 67 72 61 6d 20 63 6f |c the program co|
00003a20 6d 70 61 72 65 73 20 74 68 65 20 66 69 72 73 74 |mpares the first|
00003a30 20 26 31 30 30 20 62 79 74 65 73 20 6f 66 20 74 | &100 bytes of t|
00003a40 68 65 20 69 6d 61 67 65 20 77 69 74 68 0d 26 31 |he image with.&1|
00003a50 30 30 20 62 79 74 65 73 20 38 6b 20 68 69 67 68 |00 bytes 8k high|
00003a60 65 72 20 69 6e 20 6d 65 6d 6f 72 79 20 28 6c 69 |er in memory (li|
00003a70 6e 65 73 20 31 30 39 30 2d 31 31 31 30 29 2e 20 |nes 1090-1110). |
00003a80 49 66 20 65 76 65 72 79 20 70 61 69 72 20 6f 66 |If every pair of|
00003a90 0d 26 31 30 30 20 62 79 74 65 73 20 69 73 20 69 |.&100 bytes is i|
00003aa0 64 65 6e 74 69 63 61 6c 20 74 68 65 20 72 6f 6d |dentical the rom|
00003ab0 20 69 73 20 72 65 63 6f 67 6e 69 73 65 64 20 61 | is recognised a|
00003ac0 73 20 61 6e 20 38 6b 20 69 6d 61 67 65 20 61 6e |s an 8k image an|
00003ad0 64 20 6f 6e 6c 79 0d 74 68 65 20 66 69 72 73 74 |d only.the first|
00003ae0 20 26 32 30 30 30 20 62 79 74 65 73 20 61 72 65 | &2000 bytes are|
00003af0 20 73 61 76 65 64 2e 0d 0d 20 20 54 68 65 20 70 | saved... The p|
00003b00 72 6f 67 72 61 6d 20 52 45 41 44 52 4f 4d 2c 20 |rogram READROM, |
00003b10 61 73 20 77 65 6c 6c 20 61 73 20 69 6c 6c 75 73 |as well as illus|
00003b20 74 72 61 74 69 6e 67 20 74 68 65 20 74 65 63 68 |trating the tech|
00003b30 6e 69 71 75 65 73 0d 64 65 73 63 72 69 62 65 64 |niques.described|
00003b40 20 61 62 6f 76 65 2c 20 77 69 6c 6c 20 62 65 20 | above, will be |
00003b50 75 73 65 66 75 6c 20 69 6e 20 6c 61 74 65 72 20 |useful in later |
00003b60 6d 6f 64 75 6c 65 73 20 77 68 65 6e 20 79 6f 75 |modules when you|
00003b70 20 77 69 6c 6c 20 77 61 6e 74 20 74 6f 0d 65 78 | will want to.ex|
00003b80 61 6d 69 6e 65 20 6f 72 20 73 61 76 65 20 74 68 |amine or save th|
00003b90 65 20 63 6f 6e 74 65 6e 74 73 20 6f 66 20 73 69 |e contents of si|
00003ba0 64 65 77 61 79 73 20 72 61 6d 20 62 61 6e 6b 73 |deways ram banks|
00003bb0 2e 20 54 68 65 20 70 72 6f 67 72 61 6d 20 63 61 |. The program ca|
00003bc0 6e 20 62 65 0d 6d 6f 64 69 66 69 65 64 20 74 6f |n be.modified to|
00003bd0 20 70 72 6f 64 75 63 65 20 61 6e 6f 74 68 65 72 | produce another|
00003be0 20 70 72 6f 67 72 61 6d 20 74 6f 20 6c 6f 61 64 | program to load|
00003bf0 20 72 6f 6d 20 69 6d 61 67 65 73 20 69 6e 74 6f | rom images into|
00003c00 20 61 6e 79 0d 73 69 64 65 77 61 79 73 20 72 61 | any.sideways ra|
00003c10 6d 20 62 61 6e 6b 2c 20 69 6e 63 6c 75 64 69 6e |m bank, includin|
00003c20 67 20 74 68 65 20 70 61 67 65 64 20 6d 65 6d 6f |g the paged memo|
00003c30 72 79 20 62 61 6e 6b 20 6f 66 20 74 68 65 20 42 |ry bank of the B|
00003c40 42 43 20 42 2b 2e 20 54 68 69 73 0d 68 61 73 20 |BC B+. This.has |
00003c50 62 65 65 6e 20 6c 65 66 74 20 61 73 20 61 6e 20 |been left as an |
00003c60 65 78 65 72 63 69 73 65 20 66 6f 72 20 79 6f 75 |exercise for you|
00003c70 20 74 6f 20 63 6f 6d 70 6c 65 74 65 2e 0d 0d 0d | to complete....|
00003c80 0d 20 20 20 31 30 20 52 45 4d 3a 20 52 45 41 44 |. 10 REM: READ|
00003c90 52 4f 4d 0d 20 20 20 32 30 20 4d 4f 44 45 37 0d |ROM. 20 MODE7.|
00003ca0 20 20 20 33 30 20 48 49 4d 45 4d 3d 26 33 43 30 | 30 HIMEM=&3C0|
00003cb0 30 0d 20 20 20 34 30 20 44 49 4d 20 6d 63 6f 64 |0. 40 DIM mcod|
00003cc0 65 20 26 31 30 30 0d 20 20 20 35 30 20 73 65 6c |e &100. 50 sel|
00003cd0 65 63 74 3d 26 46 45 33 30 0d 20 20 20 36 30 20 |ect=&FE30. 60 |
00003ce0 6f 73 72 64 72 6d 3d 26 46 46 42 39 0d 20 20 20 |osrdrm=&FFB9. |
00003cf0 37 30 20 6f 73 61 73 63 69 3d 26 46 46 45 33 0d |70 osasci=&FFE3.|
00003d00 20 20 20 38 30 20 6f 73 62 79 74 65 3d 26 46 46 | 80 osbyte=&FF|
00003d10 46 34 0d 20 20 20 39 30 20 6f 73 63 6c 69 3d 26 |F4. 90 oscli=&|
00003d20 46 46 46 37 0d 20 20 31 30 30 20 63 6f 70 79 3d |FFF7. 100 copy=|
00003d30 26 37 30 0d 20 20 31 31 30 20 74 65 6d 70 3d 26 |&70. 110 temp=&|
00003d40 37 31 0d 20 20 31 32 30 20 72 65 61 64 3d 26 37 |71. 120 read=&7|
00003d50 32 0d 20 20 31 33 30 20 77 72 69 74 65 3d 26 37 |2. 130 write=&7|
00003d60 34 0d 20 20 31 34 30 20 72 6f 6d 6e 75 6d 62 65 |4. 140 romnumbe|
00003d70 72 3d 26 46 34 0d 20 20 31 35 30 20 72 6f 6d 70 |r=&F4. 150 romp|
00003d80 6f 69 6e 74 3d 26 46 36 0d 20 20 31 36 30 20 4f |oint=&F6. 160 O|
00003d90 4e 20 45 52 52 4f 52 20 50 52 49 4e 54 20 3a 20 |N ERROR PRINT : |
00003da0 45 4e 44 0d 20 20 31 37 30 20 46 4f 52 20 70 61 |END. 170 FOR pa|
00003db0 73 73 3d 30 20 54 4f 20 32 20 53 54 45 50 20 32 |ss=0 TO 2 STEP 2|
00003dc0 0d 20 20 31 38 30 20 50 25 3d 6d 63 6f 64 65 0d |. 180 P%=mcode.|
00003dd0 20 20 31 39 30 20 5b 20 20 20 20 20 20 20 4f 50 | 190 [ OP|
00003de0 54 20 70 61 73 73 0d 20 20 32 30 30 20 2e 6e 75 |T pass. 200 .nu|
00003df0 6d 62 65 72 0d 20 20 32 31 30 20 20 20 20 20 20 |mber. 210 |
00003e00 20 20 20 4c 44 41 20 23 26 41 41 0d 20 20 32 32 | LDA #&AA. 22|
00003e10 30 20 20 20 20 20 20 20 20 20 4c 44 58 20 23 30 |0 LDX #0|
00003e20 0d 20 20 32 33 30 20 20 20 20 20 20 20 20 20 4c |. 230 L|
00003e30 44 59 20 23 26 46 46 0d 20 20 32 34 30 20 20 20 |DY #&FF. 240 |
00003e40 20 20 20 20 20 20 4a 53 52 20 6f 73 62 79 74 65 | JSR osbyte|
00003e50 20 20 20 20 5c 20 46 69 6e 64 20 72 6f 6d 20 74 | \ Find rom t|
00003e60 61 62 6c 65 0d 20 20 32 35 30 20 20 20 20 20 20 |able. 250 |
00003e70 20 20 20 53 54 58 20 72 65 61 64 0d 20 20 32 36 | STX read. 26|
00003e80 30 20 20 20 20 20 20 20 20 20 53 54 59 20 72 65 |0 STY re|
00003e90 61 64 2b 31 0d 20 20 32 37 30 20 20 20 20 20 20 |ad+1. 270 |
00003ea0 20 20 20 4c 44 59 20 63 6f 70 79 0d 20 20 32 38 | LDY copy. 28|
00003eb0 30 20 20 20 20 20 20 20 20 20 4c 44 41 20 28 72 |0 LDA (r|
00003ec0 65 61 64 29 2c 59 0d 20 20 32 39 30 20 20 20 20 |ead),Y. 290 |
00003ed0 20 20 20 20 20 42 45 51 20 66 69 6e 69 73 68 0d | BEQ finish.|
00003ee0 20 20 33 30 30 20 20 20 20 20 20 20 20 20 4c 44 | 300 LD|
00003ef0 41 20 23 38 0d 20 20 33 31 30 20 20 20 20 20 20 |A #8. 310 |
00003f00 20 20 20 53 54 41 20 72 6f 6d 70 6f 69 6e 74 0d | STA rompoint.|
00003f10 20 20 33 32 30 20 20 20 20 20 20 20 20 20 4c 44 | 320 LD|
00003f20 41 20 23 26 38 30 0d 20 20 33 33 30 20 20 20 20 |A #&80. 330 |
00003f30 20 20 20 20 20 53 54 41 20 72 6f 6d 70 6f 69 6e | STA rompoin|
00003f40 74 2b 31 0d 20 20 33 34 30 20 2e 72 65 61 64 6e |t+1. 340 .readn|
00003f50 61 6d 65 0d 20 20 33 35 30 20 20 20 20 20 20 20 |ame. 350 |
00003f60 20 20 49 4e 43 20 72 6f 6d 70 6f 69 6e 74 0d 20 | INC rompoint. |
00003f70 20 33 36 30 20 20 20 20 20 20 20 20 20 4c 44 59 | 360 LDY|
00003f80 20 63 6f 70 79 0d 20 20 33 37 30 20 20 20 20 20 | copy. 370 |
00003f90 20 20 20 20 4a 53 52 20 6f 73 72 64 72 6d 0d 20 | JSR osrdrm. |
00003fa0 20 33 38 30 20 20 20 20 20 20 20 20 20 43 4d 50 | 380 CMP|
00003fb0 20 23 41 53 43 28 22 20 22 29 0d 20 20 33 39 30 | #ASC(" "). 390|
00003fc0 20 20 20 20 20 20 20 20 20 42 43 43 20 66 69 6e | BCC fin|
00003fd0 69 73 68 0d 20 20 34 30 30 20 20 20 20 20 20 20 |ish. 400 |
00003fe0 20 20 4a 53 52 20 6f 73 61 73 63 69 0d 20 20 34 | JSR osasci. 4|
00003ff0 31 30 20 20 20 20 20 20 20 20 20 4a 4d 50 20 72 |10 JMP r|
00004000 65 61 64 6e 61 6d 65 0d 20 20 34 32 30 20 2e 66 |eadname. 420 .f|
00004010 69 6e 69 73 68 0d 20 20 34 33 30 20 20 20 20 20 |inish. 430 |
00004020 20 20 20 20 52 54 53 0d 20 20 34 34 30 20 2e 6d | RTS. 440 .m|
00004030 6f 76 65 0d 20 20 34 35 30 20 20 20 20 20 20 20 |ove. 450 |
00004040 20 20 4c 44 41 20 72 6f 6d 6e 75 6d 62 65 72 0d | LDA romnumber.|
00004050 20 20 34 36 30 20 20 20 20 20 20 20 20 20 53 54 | 460 ST|
00004060 41 20 74 65 6d 70 0d 20 20 34 37 30 20 20 20 20 |A temp. 470 |
00004070 20 20 20 20 20 4c 44 41 20 63 6f 70 79 0d 20 20 | LDA copy. |
00004080 34 38 30 20 20 20 20 20 20 20 20 20 53 54 41 20 |480 STA |
00004090 72 6f 6d 6e 75 6d 62 65 72 0d 20 20 34 39 30 20 |romnumber. 490 |
000040a0 20 20 20 20 20 20 20 20 53 54 41 20 73 65 6c 65 | STA sele|
000040b0 63 74 0d 20 20 35 30 30 20 20 20 20 20 20 20 20 |ct. 500 |
000040c0 20 4c 44 41 20 23 26 38 30 0d 20 20 35 31 30 20 | LDA #&80. 510 |
000040d0 20 20 20 20 20 20 20 20 53 54 41 20 72 65 61 64 | STA read|
000040e0 2b 31 0d 20 20 35 32 30 20 20 20 20 20 20 20 20 |+1. 520 |
000040f0 20 4c 44 41 20 23 26 33 43 0d 20 20 35 33 30 20 | LDA #&3C. 530 |
00004100 20 20 20 20 20 20 20 20 53 54 41 20 77 72 69 74 | STA writ|
00004110 65 2b 31 0d 20 20 35 34 30 20 20 20 20 20 20 20 |e+1. 540 |
00004120 20 20 4c 44 59 20 23 30 0d 20 20 35 35 30 20 20 | LDY #0. 550 |
00004130 20 20 20 20 20 20 20 53 54 59 20 72 65 61 64 0d | STY read.|
00004140 20 20 35 36 30 20 20 20 20 20 20 20 20 20 53 54 | 560 ST|
00004150 59 20 77 72 69 74 65 0d 20 20 35 37 30 20 2e 72 |Y write. 570 .r|
00004160 65 6c 6f 63 61 74 65 0d 20 20 35 38 30 20 20 20 |elocate. 580 |
00004170 20 20 20 20 20 20 4c 44 41 20 28 72 65 61 64 29 | LDA (read)|
00004180 2c 59 0d 20 20 35 39 30 20 20 20 20 20 20 20 20 |,Y. 590 |
00004190 20 53 54 41 20 28 77 72 69 74 65 29 2c 59 0d 20 | STA (write),Y. |
000041a0 20 36 30 30 20 20 20 20 20 20 20 20 20 49 4e 59 | 600 INY|
000041b0 0d 20 20 36 31 30 20 20 20 20 20 20 20 20 20 42 |. 610 B|
000041c0 4e 45 20 72 65 6c 6f 63 61 74 65 0d 20 20 36 32 |NE relocate. 62|
000041d0 30 20 20 20 20 20 20 20 20 20 49 4e 43 20 72 65 |0 INC re|
000041e0 61 64 2b 31 0d 20 20 36 33 30 20 20 20 20 20 20 |ad+1. 630 |
000041f0 20 20 20 49 4e 43 20 77 72 69 74 65 2b 31 0d 20 | INC write+1. |
00004200 20 36 34 30 20 20 20 20 20 20 20 20 20 4c 44 41 | 640 LDA|
00004210 20 72 65 61 64 2b 31 0d 20 20 36 35 30 20 20 20 | read+1. 650 |
00004220 20 20 20 20 20 20 43 4d 50 20 23 26 43 30 0d 20 | CMP #&C0. |
00004230 20 36 36 30 20 20 20 20 20 20 20 20 20 42 4e 45 | 660 BNE|
00004240 20 72 65 6c 6f 63 61 74 65 0d 20 20 36 37 30 20 | relocate. 670 |
00004250 20 20 20 20 20 20 20 20 4c 44 41 20 74 65 6d 70 | LDA temp|
00004260 0d 20 20 36 38 30 20 20 20 20 20 20 20 20 20 53 |. 680 S|
00004270 54 41 20 72 6f 6d 6e 75 6d 62 65 72 0d 20 20 36 |TA romnumber. 6|
00004280 39 30 20 20 20 20 20 20 20 20 20 53 54 41 20 73 |90 STA s|
00004290 65 6c 65 63 74 0d 20 20 37 30 30 20 20 20 20 20 |elect. 700 |
000042a0 20 20 20 20 52 54 53 0d 20 20 37 31 30 20 5d 0d | RTS. 710 ].|
000042b0 20 20 37 32 30 20 4e 45 58 54 0d 20 20 37 33 30 | 720 NEXT. 730|
000042c0 20 46 4f 52 20 73 6f 63 6b 65 74 3d 30 20 54 4f | FOR socket=0 TO|
000042d0 20 31 35 0d 20 20 37 34 30 20 3f 63 6f 70 79 3d | 15. 740 ?copy=|
000042e0 73 6f 63 6b 65 74 0d 20 20 37 35 30 20 49 46 20 |socket. 750 IF |
000042f0 73 6f 63 6b 65 74 3c 31 30 20 50 52 49 4e 54 3b |socket<10 PRINT;|
00004300 22 20 22 3b 0d 20 20 37 36 30 20 50 52 49 4e 54 |" ";. 760 PRINT|
00004310 3b 73 6f 63 6b 65 74 3b 22 20 22 3b 0d 20 20 37 |;socket;" ";. 7|
00004320 37 30 20 43 41 4c 4c 20 6e 75 6d 62 65 72 0d 20 |70 CALL number. |
00004330 20 37 38 30 20 50 52 49 4e 54 0d 20 20 37 39 30 | 780 PRINT. 790|
00004340 20 4e 45 58 54 0d 20 20 38 30 30 20 56 44 55 31 | NEXT. 800 VDU1|
00004350 34 0d 20 20 38 31 30 20 52 45 50 45 41 54 0d 20 |4. 810 REPEAT. |
00004360 20 38 32 30 20 49 4e 50 55 54 27 22 57 68 69 63 | 820 INPUT'"Whic|
00004370 68 20 52 4f 4d 20 26 28 30 2d 31 35 29 20 22 73 |h ROM &(0-15) "s|
00004380 6f 63 6b 65 74 0d 20 20 38 33 30 20 55 4e 54 49 |ocket. 830 UNTI|
00004390 4c 20 73 6f 63 6b 65 74 20 3e 3d 20 30 20 41 4e |L socket >= 0 AN|
000043a0 44 20 73 6f 63 6b 65 74 20 3c 20 31 36 0d 20 20 |D socket < 16. |
000043b0 38 34 30 20 3f 63 6f 70 79 3d 73 6f 63 6b 65 74 |840 ?copy=socket|
000043c0 0d 20 20 38 35 30 20 43 41 4c 4c 20 6d 6f 76 65 |. 850 CALL move|
000043d0 0d 20 20 38 36 30 20 50 52 49 4e 54 27 22 3c 53 |. 860 PRINT'"<S|
000043e0 48 49 46 54 3e 20 74 6f 20 73 63 72 6f 6c 6c 2c |HIFT> to scroll,|
000043f0 20 3c 45 53 43 41 50 45 3e 20 74 6f 20 65 78 69 | <ESCAPE> to exi|
00004400 74 22 0d 20 20 38 37 30 20 4f 4e 20 45 52 52 4f |t". 870 ON ERRO|
00004410 52 20 50 52 4f 43 73 61 76 65 0d 20 20 38 38 30 |R PROCsave. 880|
00004420 20 46 4f 52 20 62 6c 6f 63 6b 3d 26 33 43 30 30 | FOR block=&3C00|
00004430 20 54 4f 20 26 37 42 46 46 20 53 54 45 50 20 38 | TO &7BFF STEP 8|
00004440 0d 20 20 38 39 30 20 50 52 49 4e 54 27 3b 7e 62 |. 890 PRINT';~b|
00004450 6c 6f 63 6b 2b 26 34 34 30 30 3b 22 20 20 22 3b |lock+&4400;" ";|
00004460 0d 20 20 39 30 30 20 46 4f 52 20 6d 65 6d 6f 72 |. 900 FOR memor|
00004470 79 3d 30 20 54 4f 20 37 0d 20 20 39 31 30 20 62 |y=0 TO 7. 910 b|
00004480 79 74 65 3d 62 6c 6f 63 6b 3f 6d 65 6d 6f 72 79 |yte=block?memory|
00004490 0d 20 20 39 32 30 20 49 46 20 62 79 74 65 3c 31 |. 920 IF byte<1|
000044a0 36 20 56 44 55 34 38 0d 20 20 39 33 30 20 50 52 |6 VDU48. 930 PR|
000044b0 49 4e 54 3b 7e 62 79 74 65 3b 22 20 22 3b 0d 20 |INT;~byte;" ";. |
000044c0 20 39 34 30 20 4e 45 58 54 0d 20 20 39 35 30 20 | 940 NEXT. 950 |
000044d0 46 4f 52 20 6d 65 6d 6f 72 79 3d 30 20 54 4f 20 |FOR memory=0 TO |
000044e0 37 0d 20 20 39 36 30 20 62 79 74 65 3d 6d 65 6d |7. 960 byte=mem|
000044f0 6f 72 79 3f 62 6c 6f 63 6b 0d 20 20 39 37 30 20 |ory?block. 970 |
00004500 49 46 20 62 79 74 65 3e 33 31 20 41 4e 44 20 62 |IF byte>31 AND b|
00004510 79 74 65 3c 31 32 37 20 56 44 55 62 79 74 65 20 |yte<127 VDUbyte |
00004520 45 4c 53 45 20 56 44 55 34 36 0d 20 20 39 38 30 |ELSE VDU46. 980|
00004530 20 4e 45 58 54 0d 20 20 39 39 30 20 4e 45 58 54 | NEXT. 990 NEXT|
00004540 0d 20 31 30 30 30 20 50 52 4f 43 73 61 76 65 0d |. 1000 PROCsave.|
00004550 20 31 30 31 30 20 45 4e 44 0d 20 31 30 32 30 20 | 1010 END. 1020 |
00004560 44 45 46 50 52 4f 43 73 61 76 65 0d 20 31 30 33 |DEFPROCsave. 103|
00004570 30 20 4f 4e 20 45 52 52 4f 52 20 50 52 49 4e 54 |0 ON ERROR PRINT|
00004580 20 3a 20 45 4e 44 0d 20 31 30 34 30 20 56 44 55 | : END. 1040 VDU|
00004590 31 35 0d 20 31 30 35 30 20 49 4e 50 55 54 27 27 |15. 1050 INPUT''|
000045a0 22 53 61 76 65 20 52 4f 4d 3f 20 28 59 2f 4e 29 |"Save ROM? (Y/N)|
000045b0 20 22 79 65 73 24 0d 20 31 30 36 30 20 52 45 50 | "yes$. 1060 REP|
000045c0 45 41 54 0d 20 31 30 37 30 20 49 46 20 79 65 73 |EAT. 1070 IF yes|
000045d0 24 3d 22 59 22 20 49 4e 50 55 54 22 46 69 6c 65 |$="Y" INPUT"File|
000045e0 6e 61 6d 65 3f 20 3a 20 22 66 69 6c 65 6e 61 6d |name? : "filenam|
000045f0 65 24 20 45 4c 53 45 20 49 4e 50 55 54 22 41 6e |e$ ELSE INPUT"An|
00004600 0d 20 20 20 20 20 20 6f 74 68 65 72 3f 20 28 59 |. other? (Y|
00004610 2f 4e 29 20 22 79 65 73 24 20 3a 20 49 46 20 79 |/N) "yes$ : IF y|
00004620 65 73 24 3c 3e 22 59 22 20 45 4e 44 20 45 4c 53 |es$<>"Y" END ELS|
00004630 45 20 52 55 4e 0d 20 31 30 38 30 20 73 69 7a 65 |E RUN. 1080 size|
00004640 3d 46 41 4c 53 45 0d 20 31 30 39 30 20 46 4f 52 |=FALSE. 1090 FOR|
00004650 20 62 6c 6f 63 6b 3d 26 33 43 30 30 20 54 4f 20 | block=&3C00 TO |
00004660 26 33 44 30 30 0d 20 31 31 30 30 20 49 46 20 3f |&3D00. 1100 IF ?|
00004670 62 6c 6f 63 6b 20 3c 3e 20 3f 28 62 6c 6f 63 6b |block <> ?(block|
00004680 2b 26 32 30 30 30 29 20 73 69 7a 65 3d 20 54 52 |+&2000) size= TR|
00004690 55 45 0d 20 31 31 31 30 20 4e 45 58 54 0d 20 31 |UE. 1110 NEXT. 1|
000046a0 31 32 30 20 49 46 20 73 69 7a 65 3d 54 52 55 45 |120 IF size=TRUE|
000046b0 20 73 69 7a 65 3d 26 34 30 30 30 20 45 4c 53 45 | size=&4000 ELSE|
000046c0 20 73 69 7a 65 3d 26 32 30 30 30 0d 20 31 31 33 | size=&2000. 113|
000046d0 30 20 24 6d 63 6f 64 65 3d 22 53 41 56 45 20 22 |0 $mcode="SAVE "|
000046e0 2b 66 69 6c 65 6e 61 6d 65 24 2b 22 20 33 43 30 |+filename$+" 3C0|
000046f0 30 2b 22 2b 53 54 52 24 7e 28 73 69 7a 65 29 2b |0+"+STR$~(size)+|
00004700 22 20 46 46 46 46 38 30 0d 20 20 20 20 20 20 30 |" FFFF80. 0|
00004710 30 20 46 46 46 46 38 30 30 30 22 0d 20 31 31 34 |0 FFFF8000". 114|
00004720 30 20 58 25 3d 6d 63 6f 64 65 20 4d 4f 44 20 32 |0 X%=mcode MOD 2|
00004730 35 36 0d 20 31 31 35 30 20 59 25 3d 6d 63 6f 64 |56. 1150 Y%=mcod|
00004740 65 20 44 49 56 20 32 35 36 0d 20 31 31 36 30 20 |e DIV 256. 1160 |
00004750 43 41 4c 4c 20 6f 73 63 6c 69 0d 20 31 31 37 30 |CALL oscli. 1170|
00004760 20 79 65 73 24 3d 22 22 0d 20 31 31 38 30 20 55 | yes$="". 1180 U|
00004770 4e 54 49 4c 20 46 41 4c 53 45 0d 20 31 31 39 30 |NTIL FALSE. 1190|
00004780 20 45 4e 44 50 52 4f 43 0d | ENDPROC.|
00004789 
23_10_87/T\SWR01.m0
23_10_87/T\SWR01.m1
23_10_87/T\SWR01.m2
23_10_87/T\SWR01.m4
23_10_87/T\SWR01.m5
.