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18-09-88/T\SWR11
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 » telesoftware9.adl |
| Filename: | 18-09-88/T\SWR11 |
| Read OK: | ✔ |
| File size: | 4E46 bytes |
| Load address: | 0000 |
| Exec address: | FFFFFFFF |
Duplicates
There is 1 duplicate copy of this file in the archive:
- CEEFAX disks » telesoftware4.adl » 10-01-88/T\SWR11
- CEEFAX disks » telesoftware9.adl » 18-09-88/T\SWR11
File contents
Mastering Sideways ROM & RAM - Module 11 - Private workspace
------------------------------------------------------------
It is often necessary for SWR programs to use ram workspace to store
various values and addresses. The ram within the SWR bank can only be
used for this purpose if it is not write protected and if the values
stored do not need to be accessed by other paged roms. If you intend
to write software for roms rather than sideways ram you must use ram
outside the 16k allocated to the paged roms. If you intend to write a
program which, for example, uses an Osword in the DFS then the Osword
parameter block must be in an area of memory accessable to both your
rom image and the DFS.
It is usually possible to find an area of memory which can be used
as workspace by your SWR programs. If you use a disc based BBC B you
might consider using pages &09 and &0A. These pages are usually
defined as cassette or RS423 output and input buffers but, when they
are not used for their designated purpose, they may be available to
your programs. The really big problem with using these two pages as
workspace is that you will not be the first person to have had the
idea. There are dozens of roms which use this area of memory as
workspace. If your SWR programs use it as well you have to be aware
that this area of ram will not necessarily be available for exclusive
use by your program and any data you store in it could become
corrupted by other roms or by the Acorn speech system.
Whatever area of memory you choose to use as workspace could become
corrupted by other roms unless your program claims and uses private
workspace. Private workspace starts at &1700 in BBC B computers with
the Acorn DFS and at &E00 in the BBC B without a DFS. The Master
computer makes private workspace available in paged memory overlaid on
the MOS as well as from &E00 in main memory.
In this module I will explain and demonstrate how to claim and use
private workspace in main memory. At the end of the module I will
explain how to modify these techniques to use the alternative paged
memory private workspace available in the Master computer.
In order to claim private workspace your SWR interpreter has to
intercept the private workspace service call. To demonstrate the
private workspace service call load the object code generated by the
program TRACE into SWR and press the Break key (Ctrl+Break on the
Master). A list of service calls similar to the one in figure 11.1
will be printed on the screen. Unless you use a BBC B with an Acorn
6502 Second Processor, Acorn DNFS and sideways ram in socket &0F your
trace will be different from the one in figure 11.1, but in all BBC
computers you will find service call 2, the private workspace claim,
somewhere in the list.
A=19 X=0F Y=FF SPOOL/EXEC file closure
A=0F X=0F Y=FF Vectors claimed
A=FF X=0F Y=FF Tube system main init.
A=01 X=0F Y=0E Abs. workspace claim
A=02 X=0F Y=17 Private workspace claim
A=FE X=0F Y=FF Tube system post init.
A=11 X=0F Y=1F Font implode/explode
Acorn TUBE 6502 64K
A=03 X=0F Y=08 Auto-boot
Acorn DFS
A=10 X=0F Y=EE SPOOL/EXEC file closure
A=0F X=0F Y=30 Vectors claimed
A=0A X=0F Y=D4 Claim static workspace
BASIC
>
Figure 11.1 Service call trace after Break
-------------------------------------------
In figure 11.1 you can see that the private workspace claim, service
call 2, is made with Y=&17. Private workspace starts at page &17 in
the BBC B with the Acorn DFS. If the trace is run from a lower
priority rom than the DFS rom then service call 2 will be made with
Y=&19 indicating that the DFS has claimed pages &17 and &18 as private
workspace. If the trace is run on a BBC B without a DFS then service
call 2 is made with Y=&0E indicating that private workspace is
available from &E00. The Master also makes service call 2 with Y=&0E
indicating that, if private workspace is claimed in main memory rather
than in paged memory, it also starts at &E00.
Service call 2 is issued to all the paged roms, starting with rom
&0F. It gives the roms the opportunity to claim their own private
workspace. Private workspace is allocated in pages of 256 bytes and is
exclusive to the rom claiming it. Service call 2 is made to each rom
with its rom number in the X register and the first page number of the
workspace available to it in the Y register. A rom can claim private
workspace by saving the contents of the Y register (ie. the most
significant byte of the address of the start of private workspace) in
the paged rom workspace table from &DF0 to &DFF (one byte per rom for
roms &00 to &0F respectively). It must then increment the Y register
once for each page of private workspace required. The Y register must
never be decremented when service call 2 has been intercepted.
The example coding in figure 11.2 could be used to claim one page of
private workspace.
.service
PHA \ push accumulator on stack
CMP #2 \ is it service call 2?
BNE nottwo \ branch if not 2
TYA \ prepare to store start of workspace
STA &DF0,X \ store start address in workspace table
INY \ claim 1 page of workspace
PLA \ restore accumulator
RTS \ return to MOS
.nottwo
Figure 11.2 Claiming private workspace
---------------------------------------
For obvious reasons page &0D of the I/O processor memory should
never be corrupted by using it to run programs.
Whenever a rom needs to use its private workspace it should look up
the most significant byte of the start address of the workspace in the
paged rom workspace table and access the workspace with indirect
addressing. The rom must not refer to the workspace directly because
its start address will depend on the amount of workspace claimed by
higher priority roms.
If a rom claims private workspace in main memory the value of the
Oshwm and PAGE will be raised. If, for example, your program claims 2
pages of private workspace then Oshwm and PAGE will be raised, on a
BBC B with DFS, from &1900 to &1B00. In this example, the private
workspace could start at either &1700 or &1900 depending on the
priority of your rom with respect to the DFS rom.
Your program will work properly from all rom sockets if it accesses
the private workspace indirectly after looking up the most significant
byte of the start address of private workspace in the paged rom
workspace table. This technique is illustrated in figure 11.3 which
shows how your SWR program can use post-indexed indirect addressing to
read the contents of the first byte of its private workspace.
LDX &F4 \ load X with rom number
LDA &DF0,X \ find most sig. byte of workspace address
STA &71 \ store it for indirect addressing
LDA #0 \ workspace always starts at a page boundary
STA &70 \ store least sig. byte of workspace address
TAY \ Y = 0
LDA (&70),Y \ Read first byte of private workspace
Figure 11.3 Reading private workspace
--------------------------------------
The techniques illustrated in figures 11.2 and 11.3 have been used
in the program PRIVATE. This program claims one page of private
workspace to use for an Osword parameter block.
Osword &7D, one of the DFS Oswords, is used to demonstrate how your
SWR programs can use Osword routines in other paged roms. In order to
use Osword calls in this way the parameter block must be accessed by
both roms, it cannot be within the paged ram bank used by the SWR
program. Private workspace in main memory is claimed by the program
PRIVATE but it is made available to the DFS by specifying its address
in the X and Y registers before calling Osword &7D. The private
workspace will not be available to the DFS, or any other rom, unless
the program which claimed the workspace makes it available in this
way.
Osword &7D reads the catalogue for the current default disc drive.
From this it extracts the number of times that disc has been written.
This is known as the disc cycles. The number of cycles is available as
a binary coded decimal number in a one byte parameter block specified
by the X and Y registers on entry to Osword &7D.
To use the program PRIVATE load the object code it generates into
SWR and press the Break key. Type PRINT ~ PAGE and press Return. You
will see that PAGE has been raised from &1900 to &1A00 (BBC B with
Acorn DFS). Type *CYCLES and press Return. The program will read the
current default disc drive and print the number of cycles.
The program uses the unrecognised * command interpreter (lines
410-680) and error routine (lines 1080-1230) introduced in earlier
modules of the course.
One page of private workspace is claimed in lines 330 to 400. The
start of the workspace is stored in the paged rom workspace table
(line 370) and the Y register is incremented once (line 380) to
indicate that the minimum one page of private workspace is required.
Only one byte of the one page is used by the program but workspace is
only available in units of 256 bytes.
When the unrecognised * command interpreter recognises the command
*CYCLES control is passed to the label ".found" (line 690). The
program stores the contents of the two zero page bytes it uses by
pushing them on the stack (lines 700-730) and then uses Osargs to see
if the DFS is active (lines 740-790). If the DFS is not active control
is passed to the error routine (lines 1080-1230) which, after
restoring the zero page bytes, halts the program and prints an error
message.
If the DFS is active the most significant byte of the address of the
start of private workspace is read from the paged rom workspace table
(lines 800-810) and stored in the most significant of the two zero
page bytes (line 820). These two zero page bytes are used later in the
program to read the contents of the parameter block.
The accumulator is transfered to the Y register (line 830) to make
the most significant byte of the parameter block address available to
Osword. The X register is loaded with zero (line 840) to make the
least significant byte of the parameter block address available to
Osword and X is stored in the least significant byte of the two zero
page bytes (line 850).
Osword &7D is called (lines 860-870) and the result is read from the
parameter block in the first byte of the private workspace (lines
880-890). The result is printed (line 900 and lines 1240-1390) with a
suitable message (lines 910-970). The zero page memory locations are
restored (lines 990-1020), the stack is balanced (lines 1030-1050) and
control is returned to the MOS after reseting the accumulator to zero
to indicate that the command has been recognised (lines 1060-1070).
10 REM: PRIVATE
20 MODE7
30 HIMEM=&3C00
40 DIM save 50
50 diff=&8000-HIMEM
60 address=&70
70 comvec=&F2
80 errstack=&100
90 romnumber=&F4
100 workspace=&DF0
110 gsread=&FFC5
120 osargs=&FFDA
130 osasci=&FFE3
140 osword=&FFF1
150 oscli=&FFF7
160 FOR pass = 0 TO 2 STEP 2
170 P%=HIMEM
180 [ OPT pass
190 BRK
200 BRK
210 BRK
220 JMP service+diff
230 OPT FNequb(&82)
240 OPT FNequb((copyright+diff) MOD 256)
250 BRK
260 .title
270 OPT FNequs("CYCLES")
280 .copyright
290 BRK
300 OPT FNequs("(C) Gordon Horsington 1987")
310 BRK
320 .service
330 PHA
340 CMP #2
350 BNE tryfour
360 TYA
370 STA workspace,X
380 INY
390 PLA
400 RTS
410 .tryfour
420 CMP #4
430 BEQ unrecognised
440 PLA
450 RTS
460 .unrecognised
470 TXA
480 PHA
490 TYA
500 PHA
510 LDX #&FF
520 .comloop
530 INX
540 LDA title+diff,X
550 BEQ found
560 LDA (comvec),Y
570 INY
580 CMP #ASC(".")
590 BEQ found
600 AND #&DF
610 CMP title+diff,X
620 BEQ comloop
630 PLA
640 TAY
650 PLA
660 TAX
670 PLA
680 RTS
690 .found
700 LDA address
710 PHA
720 LDA address+1
730 PHA
740 LDA #0
750 TAX
760 TAY
770 JSR osargs
780 CMP #4 \ Is DFS active?
790 BNE error
800 LDX romnumber
810 LDA workspace,X \ MSB of workspace
820 STA address+1
830 TAY \ MSB for Osword
840 LDX #0 \ LSB of workspace
850 STX address
860 LDA #&7D
870 JSR osword \ Read disc cycles
880 LDY #0
890 LDA (address),Y \ Read result
900 JSR hexbyte+diff
910 LDX #&FF
920 .printloop
930 INX
940 LDA message+diff,X
950 BEQ quit
960 JSR osasci
970 JMP printloop+diff
980 .quit
990 PLA
1000 STA address+1
1010 PLA
1020 STA address
1030 PLA
1040 PLA
1050 PLA
1060 LDA #0
1070 RTS
1080 .error
1090 LDA #(wrong+diff) MOD 256
1100 STA address
1110 LDA #(wrong+diff) DIV 256
1120 STA address+1
1130 LDY #&FF
1140 .errorloop
1150 INY
1160 LDA (address),Y
1170 STA errstack,Y
1180 BPL errorloop
1190 PLA
1200 STA address+1
1210 PLA
1220 STA address
1230 JMP errstack
1240 .hexbyte
1250 PHA
1260 LSR A
1270 LSR A
1280 LSR A
1290 LSR A
1300 JSR nybble+diff
1310 PLA
1320 .nybble
1330 AND #&0F
1340 SED
1350 CLC
1360 ADC #&90
1370 ADC #&40
1380 CLD
1390 JMP osasci
1400 .message
1410 OPT FNequs(" Disc cycles")
1420 OPT FNequb(&0D)
1430 BRK
1440 .wrong
1450 BRK
1460 BRK
1470 OPT FNequs("DFS not active")
1480 BRK
1490 OPT FNequb(&FF)
1500 .lastbyte
1510 ]
1520 NEXT
1530 INPUT'"Save filename = "filename$
1540 IF filename$="" END
1550 $save="SAVE "+filename$+" "+STR$~(HIMEM)+" "+STR$~(las
tbyte)+" FFFF8000 FFFF8000"
1560 X%=save MOD 256
1570 Y%=save DIV 256
1580 *OPT1,2
1590 CALL oscli
1600 *OPT1,0
1610 END
1620 DEFFNequb(byte)
1630 ?P%=byte
1640 P%=P%+1
1650 =pass
1660 DEFFNequw(word)
1670 ?P%=word MOD 256
1680 P%?1=word DIV 256
1690 P%=P%+2
1700 =pass
1710 DEFFNequd(double)
1720 !P%=double
1730 P%=P%+4
1740 =pass
1750 DEFFNequs(string$)
1760 $P%=string$
1770 P%=P%+LEN(string$)
1780 =pass
The techniques illustrated in figures 11.2 and 11.3 and demonstrated
in the program PRIVATE need to be modified to use the alternative
paged memory private workspace available in the Master series of
computers.
In Module 1 of the course I explained how setting bit 3 of the paged
memory select register at &FE34 can be used to overlay the paged
memory from &C000 to &DFFF onto the MOS so that it appears above the
currently selected paged rom. The paged memory private workspace is
available in this area of paged memory.
The Master uses service call &24 to give the roms the opportunity to
request paged private workspace followed by service call &22 to claim
the requested paged private workspace. The coding in figure 11.2 and
11.3 needs to be modified as shown in figures 11.4 and 11.5 if your
Master SWR program needs to use paged private workspace.
.service
CMP #&24 \ is it service call &24?
BNE try22 \ branch if not &24
INY \ request 1 page of workspace
RTS \ and return
.try22
CMP #&22 \ is it service call &22?
BNE not22 \ branch if not &22
PHA \ push accumulator on stack
TYA \ prepare to store start of workspace
STA &DF0,X \ store start of workspace
PLA \ restore accumulator
RTS \ return to MOS
.not22
Figure 11.4 Claiming paged private workspace on the Master.
------------------------------------------------------------
Claiming paged memory private workspace is a bit more involved than
claiming private workspace in user memory. Your Master SWR program has
to intercept service calls &24 and &22 instead of service call 2.
Service calls &24 and &22 are not issued on the BBC B.
Intercepting service calls &24 and &22 is illustrated in figure
11.4. If your SWR program uses paged private workspace it must use
service call &22 to claim only the number of pages requested with
service call &24. The amount of claimed paged private workspace must
agree with the amount of requested paged private workspace.
A Master SWR program must not use both service call 2 and service
calls &24 and &22 to claim private workspace. You should also be aware
that, if you use service calls &24 and &22 to request and claim more
paged private workspace than is available in the paged memory, private
workspace will be claimed from user memory starting at &E00. This has
the effect of raising Oshwm and PAGE even when paged private workspace
is requested and claimed.
Using paged memory private workspace in the Master is a bit more
complicated than claiming it. Before attempting to read or write the
contents of the paged private workspace, the SWR program must first
set bit 3 of the paged memory select register at &FE34 to switch the
paged memory into the main memory map. To set bit 3 of &FE34 load the
accumulator with &08 (0000 1000 binary), OR the accumulator with the
contents of &FE34 and store the accumulator in &FE34.
To switch the paged private workspace out of the main memory map it
is necessary to clear bit 3 of the paged memory select register. To
clear bit 3 of &FE34 load the accumulator with &F7 (1111 0111 binary),
AND the accumulator with the contents of &FE34 and store the
accumulator in &FE34. If you use the subroutines illustrated in figure
11.5 the paged memory can be switched in and out of the main memory
map without altering any of the other bits in the paged memory select
register.
LDX &F4 \ load X with rom number
LDA &DF0,X \ find most sig. byte of workspace address
STA &71 \ store it for indirect addressing
LDA #0 \ workspace always starts at a page boundary
STA &70 \ store least sig. byte of workspace address
JSR pagein \ switch paged workspace in
LDY #0
LDA (address),Y \ Read first byte of private workspace
JSR pageout \ switch paged workspace out
.
.
.
.pagein
PHA
LDA #8 \ 0000 1000 binary
ORA &FE34
STA &FE34 \ set bit 3 of &FE34
PLA \ restore accumulator
RTS
.pageout
PHA
LDA #&F7 \ 1111 0111 binary
AND &FE34
STA &FE34 \ clear bit 3 of &FE34
PLA \ restore accumulator
RTS
Figure 11.5 Reading paged private workspace on the Master.
-----------------------------------------------------------
Figure 11.5 illustrates how the two subroutines, pagein and pageout,
should be used to switch the paged memory in and out of the main
memory map when reading the contents of the paged private workspace in
the Master series computers.
After switching the paged memory into the main memory map you must
be very careful about using MOS subroutines because the bottom 7.25k
of the MOS has been replaced with the paged memory. You would be wise
not to use the MOS at all until it has been restored by calling
pageout.
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 31 31 20 2d 20 50 72 69 76 61 |odule 11 - Priva|
00000030 74 65 20 77 6f 72 6b 73 70 61 63 65 0d 2d 2d 2d |te workspace.---|
00000040 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d |----------------|
*
00000070 2d 2d 2d 2d 2d 2d 2d 2d 2d 0d 0d 20 20 49 74 20 |---------.. It |
00000080 69 73 20 6f 66 74 65 6e 20 6e 65 63 65 73 73 61 |is often necessa|
00000090 72 79 20 66 6f 72 20 53 57 52 20 70 72 6f 67 72 |ry for SWR progr|
000000a0 61 6d 73 20 74 6f 20 75 73 65 20 72 61 6d 20 77 |ams to use ram w|
000000b0 6f 72 6b 73 70 61 63 65 20 74 6f 20 73 74 6f 72 |orkspace to stor|
000000c0 65 0d 76 61 72 69 6f 75 73 20 76 61 6c 75 65 73 |e.various values|
000000d0 20 61 6e 64 20 61 64 64 72 65 73 73 65 73 2e 20 | and addresses. |
000000e0 54 68 65 20 72 61 6d 20 77 69 74 68 69 6e 20 74 |The ram within t|
000000f0 68 65 20 53 57 52 20 62 61 6e 6b 20 63 61 6e 20 |he SWR bank can |
00000100 6f 6e 6c 79 20 62 65 0d 75 73 65 64 20 66 6f 72 |only be.used for|
00000110 20 74 68 69 73 20 70 75 72 70 6f 73 65 20 69 66 | this purpose if|
00000120 20 69 74 20 69 73 20 6e 6f 74 20 77 72 69 74 65 | it is not write|
00000130 20 70 72 6f 74 65 63 74 65 64 20 61 6e 64 20 69 | protected and i|
00000140 66 20 74 68 65 20 76 61 6c 75 65 73 0d 73 74 6f |f the values.sto|
00000150 72 65 64 20 64 6f 20 6e 6f 74 20 6e 65 65 64 20 |red do not need |
00000160 74 6f 20 62 65 20 61 63 63 65 73 73 65 64 20 62 |to be accessed b|
00000170 79 20 6f 74 68 65 72 20 70 61 67 65 64 20 72 6f |y other paged ro|
00000180 6d 73 2e 20 49 66 20 79 6f 75 20 69 6e 74 65 6e |ms. If you inten|
00000190 64 0d 74 6f 20 77 72 69 74 65 20 73 6f 66 74 77 |d.to write softw|
000001a0 61 72 65 20 66 6f 72 20 72 6f 6d 73 20 72 61 74 |are for roms rat|
000001b0 68 65 72 20 74 68 61 6e 20 73 69 64 65 77 61 79 |her than sideway|
000001c0 73 20 72 61 6d 20 79 6f 75 20 6d 75 73 74 20 75 |s ram you must u|
000001d0 73 65 20 72 61 6d 0d 6f 75 74 73 69 64 65 20 74 |se ram.outside t|
000001e0 68 65 20 31 36 6b 20 61 6c 6c 6f 63 61 74 65 64 |he 16k allocated|
000001f0 20 74 6f 20 74 68 65 20 70 61 67 65 64 20 72 6f | to the paged ro|
00000200 6d 73 2e 20 49 66 20 79 6f 75 20 69 6e 74 65 6e |ms. If you inten|
00000210 64 20 74 6f 20 77 72 69 74 65 20 61 0d 70 72 6f |d to write a.pro|
00000220 67 72 61 6d 20 77 68 69 63 68 2c 20 66 6f 72 20 |gram which, for |
00000230 65 78 61 6d 70 6c 65 2c 20 75 73 65 73 20 61 6e |example, uses an|
00000240 20 4f 73 77 6f 72 64 20 69 6e 20 74 68 65 20 44 | Osword in the D|
00000250 46 53 20 74 68 65 6e 20 74 68 65 20 4f 73 77 6f |FS then the Oswo|
00000260 72 64 0d 70 61 72 61 6d 65 74 65 72 20 62 6c 6f |rd.parameter blo|
00000270 63 6b 20 6d 75 73 74 20 62 65 20 69 6e 20 61 6e |ck must be in an|
00000280 20 61 72 65 61 20 6f 66 20 6d 65 6d 6f 72 79 20 | area of memory |
00000290 61 63 63 65 73 73 61 62 6c 65 20 74 6f 20 62 6f |accessable to bo|
000002a0 74 68 20 79 6f 75 72 0d 72 6f 6d 20 69 6d 61 67 |th your.rom imag|
000002b0 65 20 61 6e 64 20 74 68 65 20 44 46 53 2e 0d 0d |e and the DFS...|
000002c0 20 20 49 74 20 69 73 20 75 73 75 61 6c 6c 79 20 | It is usually |
000002d0 70 6f 73 73 69 62 6c 65 20 74 6f 20 66 69 6e 64 |possible to find|
000002e0 20 61 6e 20 61 72 65 61 20 6f 66 20 6d 65 6d 6f | an area of memo|
000002f0 72 79 20 77 68 69 63 68 20 63 61 6e 20 62 65 20 |ry which can be |
00000300 75 73 65 64 0d 61 73 20 77 6f 72 6b 73 70 61 63 |used.as workspac|
00000310 65 20 62 79 20 79 6f 75 72 20 53 57 52 20 70 72 |e by your SWR pr|
00000320 6f 67 72 61 6d 73 2e 20 49 66 20 79 6f 75 20 75 |ograms. If you u|
00000330 73 65 20 61 20 64 69 73 63 20 62 61 73 65 64 20 |se a disc based |
00000340 42 42 43 20 42 20 79 6f 75 0d 6d 69 67 68 74 20 |BBC B you.might |
00000350 63 6f 6e 73 69 64 65 72 20 75 73 69 6e 67 20 70 |consider using p|
00000360 61 67 65 73 20 26 30 39 20 61 6e 64 20 26 30 41 |ages &09 and &0A|
00000370 2e 20 54 68 65 73 65 20 70 61 67 65 73 20 61 72 |. These pages ar|
00000380 65 20 75 73 75 61 6c 6c 79 0d 64 65 66 69 6e 65 |e usually.define|
00000390 64 20 61 73 20 63 61 73 73 65 74 74 65 20 6f 72 |d as cassette or|
000003a0 20 52 53 34 32 33 20 6f 75 74 70 75 74 20 61 6e | RS423 output an|
000003b0 64 20 69 6e 70 75 74 20 62 75 66 66 65 72 73 20 |d input buffers |
000003c0 62 75 74 2c 20 77 68 65 6e 20 74 68 65 79 0d 61 |but, when they.a|
000003d0 72 65 20 6e 6f 74 20 75 73 65 64 20 66 6f 72 20 |re not used for |
000003e0 74 68 65 69 72 20 64 65 73 69 67 6e 61 74 65 64 |their designated|
000003f0 20 70 75 72 70 6f 73 65 2c 20 74 68 65 79 20 6d | purpose, they m|
00000400 61 79 20 62 65 20 61 76 61 69 6c 61 62 6c 65 20 |ay be available |
00000410 74 6f 0d 79 6f 75 72 20 70 72 6f 67 72 61 6d 73 |to.your programs|
00000420 2e 20 54 68 65 20 72 65 61 6c 6c 79 20 62 69 67 |. The really big|
00000430 20 70 72 6f 62 6c 65 6d 20 77 69 74 68 20 75 73 | problem with us|
00000440 69 6e 67 20 74 68 65 73 65 20 74 77 6f 20 70 61 |ing these two pa|
00000450 67 65 73 20 61 73 0d 77 6f 72 6b 73 70 61 63 65 |ges as.workspace|
00000460 20 69 73 20 74 68 61 74 20 79 6f 75 20 77 69 6c | is that you wil|
00000470 6c 20 6e 6f 74 20 62 65 20 74 68 65 20 66 69 72 |l not be the fir|
00000480 73 74 20 70 65 72 73 6f 6e 20 74 6f 20 68 61 76 |st person to hav|
00000490 65 20 68 61 64 20 74 68 65 0d 69 64 65 61 2e 20 |e had the.idea. |
000004a0 54 68 65 72 65 20 61 72 65 20 64 6f 7a 65 6e 73 |There are dozens|
000004b0 20 6f 66 20 72 6f 6d 73 20 77 68 69 63 68 20 75 | of roms which u|
000004c0 73 65 20 74 68 69 73 20 61 72 65 61 20 6f 66 20 |se this area of |
000004d0 6d 65 6d 6f 72 79 20 61 73 0d 77 6f 72 6b 73 70 |memory as.worksp|
000004e0 61 63 65 2e 20 49 66 20 79 6f 75 72 20 53 57 52 |ace. If your SWR|
000004f0 20 70 72 6f 67 72 61 6d 73 20 75 73 65 20 69 74 | programs use it|
00000500 20 61 73 20 77 65 6c 6c 20 79 6f 75 20 68 61 76 | as well you hav|
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00004750 6c 61 74 6f 72 20 69 6e 20 26 46 45 33 34 2e 20 |lator in &FE34. |
00004760 49 66 20 79 6f 75 20 75 73 65 20 74 68 65 20 73 |If you use the s|
00004770 75 62 72 6f 75 74 69 6e 65 73 20 69 6c 6c 75 73 |ubroutines illus|
00004780 74 72 61 74 65 64 20 69 6e 20 66 69 67 75 72 65 |trated in figure|
00004790 0d 31 31 2e 35 20 74 68 65 20 70 61 67 65 64 20 |.11.5 the paged |
000047a0 6d 65 6d 6f 72 79 20 63 61 6e 20 62 65 20 73 77 |memory can be sw|
000047b0 69 74 63 68 65 64 20 69 6e 20 61 6e 64 20 6f 75 |itched in and ou|
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000047d0 6d 6f 72 79 0d 6d 61 70 20 77 69 74 68 6f 75 74 |mory.map without|
000047e0 20 61 6c 74 65 72 69 6e 67 20 61 6e 79 20 6f 66 | altering any of|
000047f0 20 74 68 65 20 6f 74 68 65 72 20 62 69 74 73 20 | the other bits |
00004800 69 6e 20 74 68 65 20 70 61 67 65 64 20 6d 65 6d |in the paged mem|
00004810 6f 72 79 20 73 65 6c 65 63 74 0d 72 65 67 69 73 |ory select.regis|
00004820 74 65 72 2e 0d 0d 0d 0d 0d 20 20 20 20 20 20 20 |ter...... |
00004830 20 20 4c 44 58 20 26 46 34 20 20 20 20 20 20 20 | LDX &F4 |
00004840 20 20 5c 20 6c 6f 61 64 20 58 20 77 69 74 68 20 | \ load X with |
00004850 72 6f 6d 20 6e 75 6d 62 65 72 0d 20 20 20 20 20 |rom number. |
00004860 20 20 20 20 4c 44 41 20 26 44 46 30 2c 58 20 20 | LDA &DF0,X |
00004870 20 20 20 20 5c 20 66 69 6e 64 20 6d 6f 73 74 20 | \ find most |
00004880 73 69 67 2e 20 62 79 74 65 20 6f 66 20 77 6f 72 |sig. byte of wor|
00004890 6b 73 70 61 63 65 20 61 64 64 72 65 73 73 0d 20 |kspace address. |
000048a0 20 20 20 20 20 20 20 20 53 54 41 20 26 37 31 20 | STA &71 |
000048b0 20 20 20 20 20 20 20 20 5c 20 73 74 6f 72 65 20 | \ store |
000048c0 69 74 20 66 6f 72 20 69 6e 64 69 72 65 63 74 20 |it for indirect |
000048d0 61 64 64 72 65 73 73 69 6e 67 0d 20 20 20 20 20 |addressing. |
000048e0 20 20 20 20 4c 44 41 20 23 30 20 20 20 20 20 20 | LDA #0 |
000048f0 20 20 20 20 5c 20 77 6f 72 6b 73 70 61 63 65 20 | \ workspace |
00004900 61 6c 77 61 79 73 20 73 74 61 72 74 73 20 61 74 |always starts at|
00004910 20 61 20 70 61 67 65 20 62 6f 75 6e 64 61 72 79 | a page boundary|
00004920 0d 20 20 20 20 20 20 20 20 20 53 54 41 20 26 37 |. STA &7|
00004930 30 20 20 20 20 20 20 20 20 20 5c 20 73 74 6f 72 |0 \ stor|
00004940 65 20 6c 65 61 73 74 20 73 69 67 2e 20 62 79 74 |e least sig. byt|
00004950 65 20 6f 66 20 77 6f 72 6b 73 70 61 63 65 20 61 |e of workspace a|
00004960 64 64 72 65 73 73 0d 20 20 20 20 20 20 20 20 20 |ddress. |
00004970 4a 53 52 20 70 61 67 65 69 6e 20 20 20 20 20 20 |JSR pagein |
00004980 5c 20 73 77 69 74 63 68 20 70 61 67 65 64 20 77 |\ switch paged w|
00004990 6f 72 6b 73 70 61 63 65 20 69 6e 0d 20 20 20 20 |orkspace in. |
000049a0 20 20 20 20 20 4c 44 59 20 23 30 0d 20 20 20 20 | LDY #0. |
000049b0 20 20 20 20 20 4c 44 41 20 28 61 64 64 72 65 73 | LDA (addres|
000049c0 73 29 2c 59 20 5c 20 52 65 61 64 20 66 69 72 73 |s),Y \ Read firs|
000049d0 74 20 62 79 74 65 20 6f 66 20 70 72 69 76 61 74 |t byte of privat|
000049e0 65 20 77 6f 72 6b 73 70 61 63 65 0d 20 20 20 20 |e workspace. |
000049f0 20 20 20 20 20 4a 53 52 20 70 61 67 65 6f 75 74 | JSR pageout|
00004a00 20 20 20 20 20 5c 20 73 77 69 74 63 68 20 70 61 | \ switch pa|
00004a10 67 65 64 20 77 6f 72 6b 73 70 61 63 65 20 6f 75 |ged workspace ou|
00004a20 74 0d 20 20 20 20 20 20 20 20 20 20 2e 0d 20 20 |t. .. |
00004a30 20 20 20 20 20 20 20 20 2e 0d 20 20 20 20 20 20 | .. |
00004a40 20 20 20 20 2e 0d 2e 70 61 67 65 69 6e 0d 20 20 | ...pagein. |
00004a50 20 20 20 20 20 20 20 50 48 41 0d 20 20 20 20 20 | PHA. |
00004a60 20 20 20 20 4c 44 41 20 23 38 20 20 20 20 20 20 | LDA #8 |
00004a70 20 20 20 20 5c 20 30 30 30 30 20 31 30 30 30 20 | \ 0000 1000 |
00004a80 62 69 6e 61 72 79 0d 20 20 20 20 20 20 20 20 20 |binary. |
00004a90 4f 52 41 20 26 46 45 33 34 0d 20 20 20 20 20 20 |ORA &FE34. |
00004aa0 20 20 20 53 54 41 20 26 46 45 33 34 20 20 20 20 | STA &FE34 |
00004ab0 20 20 20 5c 20 73 65 74 20 62 69 74 20 33 20 6f | \ set bit 3 o|
00004ac0 66 20 26 46 45 33 34 0d 20 20 20 20 20 20 20 20 |f &FE34. |
00004ad0 20 50 4c 41 20 20 20 20 20 20 20 20 20 20 20 20 | PLA |
00004ae0 20 5c 20 72 65 73 74 6f 72 65 20 61 63 63 75 6d | \ restore accum|
00004af0 75 6c 61 74 6f 72 0d 20 20 20 20 20 20 20 20 20 |ulator. |
00004b00 52 54 53 0d 2e 70 61 67 65 6f 75 74 0d 20 20 20 |RTS..pageout. |
00004b10 20 20 20 20 20 20 50 48 41 0d 20 20 20 20 20 20 | PHA. |
00004b20 20 20 20 4c 44 41 20 23 26 46 37 20 20 20 20 20 | LDA #&F7 |
00004b30 20 20 20 5c 20 31 31 31 31 20 30 31 31 31 20 62 | \ 1111 0111 b|
00004b40 69 6e 61 72 79 0d 20 20 20 20 20 20 20 20 20 41 |inary. A|
00004b50 4e 44 20 26 46 45 33 34 0d 20 20 20 20 20 20 20 |ND &FE34. |
00004b60 20 20 53 54 41 20 26 46 45 33 34 20 20 20 20 20 | STA &FE34 |
00004b70 20 20 5c 20 63 6c 65 61 72 20 62 69 74 20 33 20 | \ clear bit 3 |
00004b80 6f 66 20 26 46 45 33 34 0d 20 20 20 20 20 20 20 |of &FE34. |
00004b90 20 20 50 4c 41 20 20 20 20 20 20 20 20 20 20 20 | PLA |
00004ba0 20 20 5c 20 72 65 73 74 6f 72 65 20 61 63 63 75 | \ restore accu|
00004bb0 6d 75 6c 61 74 6f 72 0d 20 20 20 20 20 20 20 20 |mulator. |
00004bc0 20 52 54 53 0d 0d 0d 46 69 67 75 72 65 20 31 31 | RTS...Figure 11|
00004bd0 2e 35 20 20 52 65 61 64 69 6e 67 20 70 61 67 65 |.5 Reading page|
00004be0 64 20 70 72 69 76 61 74 65 20 77 6f 72 6b 73 70 |d private worksp|
00004bf0 61 63 65 20 6f 6e 20 74 68 65 20 4d 61 73 74 65 |ace on the Maste|
00004c00 72 2e 0d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d |r..-------------|
00004c10 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d |----------------|
*
00004c30 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 2d 0d 0d |--------------..|
00004c40 20 20 46 69 67 75 72 65 20 31 31 2e 35 20 69 6c | Figure 11.5 il|
00004c50 6c 75 73 74 72 61 74 65 73 20 68 6f 77 20 74 68 |lustrates how th|
00004c60 65 20 74 77 6f 20 73 75 62 72 6f 75 74 69 6e 65 |e two subroutine|
00004c70 73 2c 20 70 61 67 65 69 6e 20 61 6e 64 20 70 61 |s, pagein and pa|
00004c80 67 65 6f 75 74 2c 0d 73 68 6f 75 6c 64 20 62 65 |geout,.should be|
00004c90 20 75 73 65 64 20 74 6f 20 73 77 69 74 63 68 20 | used to switch |
00004ca0 74 68 65 20 70 61 67 65 64 20 6d 65 6d 6f 72 79 |the paged memory|
00004cb0 20 69 6e 20 61 6e 64 20 6f 75 74 20 6f 66 20 74 | in and out of t|
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00004cd0 61 70 20 77 68 65 6e 20 72 65 61 64 69 6e 67 20 |ap when reading |
00004ce0 74 68 65 20 63 6f 6e 74 65 6e 74 73 20 6f 66 20 |the contents of |
00004cf0 74 68 65 20 70 61 67 65 64 20 70 72 69 76 61 74 |the paged privat|
00004d00 65 20 77 6f 72 6b 73 70 61 63 65 20 69 6e 0d 74 |e workspace in.t|
00004d10 68 65 20 4d 61 73 74 65 72 20 73 65 72 69 65 73 |he Master series|
00004d20 20 63 6f 6d 70 75 74 65 72 73 2e 0d 0d 20 20 41 | computers... A|
00004d30 66 74 65 72 20 73 77 69 74 63 68 69 6e 67 20 74 |fter switching t|
00004d40 68 65 20 70 61 67 65 64 20 6d 65 6d 6f 72 79 20 |he paged memory |
00004d50 69 6e 74 6f 20 74 68 65 20 6d 61 69 6e 20 6d 65 |into the main me|
00004d60 6d 6f 72 79 20 6d 61 70 20 79 6f 75 20 6d 75 73 |mory map you mus|
00004d70 74 0d 62 65 20 76 65 72 79 20 63 61 72 65 66 75 |t.be very carefu|
00004d80 6c 20 61 62 6f 75 74 20 75 73 69 6e 67 20 4d 4f |l about using MO|
00004d90 53 20 73 75 62 72 6f 75 74 69 6e 65 73 20 62 65 |S subroutines be|
00004da0 63 61 75 73 65 20 74 68 65 20 62 6f 74 74 6f 6d |cause the bottom|
00004db0 20 37 2e 32 35 6b 0d 6f 66 20 74 68 65 20 4d 4f | 7.25k.of the MO|
00004dc0 53 20 68 61 73 20 62 65 65 6e 20 72 65 70 6c 61 |S has been repla|
00004dd0 63 65 64 20 77 69 74 68 20 74 68 65 20 70 61 67 |ced with the pag|
00004de0 65 64 20 6d 65 6d 6f 72 79 2e 20 59 6f 75 20 77 |ed memory. You w|
00004df0 6f 75 6c 64 20 62 65 20 77 69 73 65 0d 6e 6f 74 |ould be wise.not|
00004e00 20 74 6f 20 75 73 65 20 74 68 65 20 4d 4f 53 20 | to use the MOS |
00004e10 61 74 20 61 6c 6c 20 75 6e 74 69 6c 20 69 74 20 |at all until it |
00004e20 68 61 73 20 62 65 65 6e 20 72 65 73 74 6f 72 65 |has been restore|
00004e30 64 20 62 79 20 63 61 6c 6c 69 6e 67 0d 70 61 67 |d by calling.pag|
00004e40 65 6f 75 74 2e 0d |eout..|
00004e46 
18-09-88/T\SWR11.m0
18-09-88/T\SWR11.m1
18-09-88/T\SWR11.m2
18-09-88/T\SWR11.m4
18-09-88/T\SWR11.m5
.