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17_10_87/B\SWR00
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: | 17_10_87/B\SWR00 |
| Read OK: | ✔ |
| File size: | 3C4D bytes |
| Load address: | 0000 |
| Exec address: | 0000 |
Duplicates
There is 1 duplicate copy of this file in the archive:
- CEEFAX disks » telesoftware3.adl » 17_10_87/B\SWR00
- CEEFAX disks » telesoftware7.adl » 24-06-88/T\SWR00
File contents
Mastering Sideways ROM & RAM - Module 00 - Preface
--------------------------------------------------
This course has been designed to provide BBC Microcomputer users
with sufficient knowledge and confidence to write software for
sideways ram (SWR) and to convert their own existing programs, in any
BBC Micro supported language, to run from the Rom Filing System (RFS).
A total of 31 BASIC 1 programs will be used to illustrate the
course. Most of these programs will be used to generate the object
code to be loaded into SWR.
The example programs can all be saved onto one side of a 100k disc.
All the programs are completely independant of their line numbers
although the numbers will be used when describing the techniques
covered in the examples. Because the programs are written in BASIC 1
they will run on all BBC model B computers as well as on the Master
and Compact computers without any modifications. Most of the programs
will also run on the Acorn Electron, which uses BASIC 2.
The programs used to illustrate the course.
-------------------------------------------
Program name: Used in modules:
ABSOL 12 Absolute workspace
ALLRFS 23 RFS
AUTORFS 22 RFS rom cartridges
BOOTRFS 19 Booting the RFS
BUFFER 14 Unrecognised interupts
CURSOR 05 Reading arguments
DEMO 18-24 All RFS modules
ENABLE 04 Enabling * commands
ENABTST 04 Demonstrate *ENABLE
ERROR 08 Errors in service code
FILES 13 Trapping errors
HELP 16 Extended help
INTLACE 12 Service code 1
LOCK 10 Program to convert to SWR
MODONE 24 Modular programming
MODTWO 24 Modular programming
NEWCOM 03 Simple * command interpreter
NOBASIC 17 Language rom design
OSBYTE 06 Unrecognised Osbyte
OSWDEMO 07 Osword demonstration
OSWORD 07 Unrecognised Osword
PEEK 09 Reading numerical arguments
PRIVATE 11 Private workspace
READROM All Examine sideways ram
RFSERV 20 RFS * commands
RFSGEN 18-24 All RFS modules
RFSHEAD 18 Simple RFS header
RFSLANG 21 RFS * commands
SOUNDS 15 Multiple command interpreter
TRACE 02-24 Service call trace
VECTOR 10 Extended rom vectors
The programs used to illustrate the course have not been designed to
use the extra memory or facilities available on the Master computer
but notes on suitable modifications have been included where
appropriate. In some cases it is necessary to press Ctrl+Break on the
Master computer when it is only necessary to press Break on the BBC B.
It is desirable, but not essential, to use a disc based system for the
RFS modules in the course. Tape only users will be given all the
information they need to use the programs.
The course modules
------------------
00. Preface. This module.
No programs.
01. Module 1 will introduce the sideways rom and ram system. The
program READROM will be used to illustrate how paged memory banks are
switched using the paged rom select register at &FE30 and its copy at
&F4. The operating system routine Osrdrm will also be used by READROM
to read individual bytes from the sideways roms.
Program: READROM
02. Module 2 will introduce the header which must be used by every rom
image and the service calls issued to every active rom. The program
TRACE will be used to illustrate how service calls are issued to the
sideways roms and to explain how service calls can be trapped in SWR
software. A summary of which service calls will be dealt with in the
course will be included in this module.
Programs: TRACE, READROM
03. A simple one-command interpreter for unrecognised * commands will
be demonstrated in module 3. The conversion of an Assembly language
sound effects program, ZAP, into a sideways ram program NEWCOM will be
explained. The new sideways ram program will replace the user memory
program by providing a new * command *ZAP to make the same sound
effect.
Programs: NEWCOM, TRACE
04. The Disc Filing System uses the command *ENABLE to protect
"dangerous" routines from accidental use. The DFS *ENABLE command can
be used from within your own sideways ram programs. This technique
will be explained and demonstrated in module 4 but it can only be
guaranteed to work in your sideways ram programs with Acorn DFS 0.9
and 1.20.
Programs: ENABLE, ENABTST
05. Arguments can follow the * command used to call a sideways ram
utility. The operating system provides two subroutines, Gsinit and
Gsread, which can be used to initialise and read an argument. Reading
arguments with Gsinit and Gsread will be explained and demonstrated in
module 5.
Program: CURSOR
06. The operating system can be used to convert the ASCII
representation of the numbers 0 to 255 into binary by defining a new
Osbyte call. This will be demonstrated with a new Osbyte call number
&64 (*FX 100). *FX100,x,y will be used to convert the x and y
parameters into binary and to store them in reserved zero page memory
locations ready to be accessed by a new routine.
Programs: OSBYTE, TRACE
07. The new Osbyte call defined in module 6 is, like all Osbyte calls,
limited to reading and writing two numerical parameters. A new Osword
can read and write as many parameters as your new routines need. This
will be demonstrated with a new Osword &64 which will read four
parameters to perform the equivalent of a 'PRINT @' routine.
Programs: OSWORD, OSWDEMO, TRACE
08. When the user of a SWR utility types an out of range or unexpected
argument it should be recognised as an error and the SWR utility
should halt any BASIC program and report an error message. This will
be demonstrated with a new command *CHECK (0-6) which will create an
error if an appropriate filing system has not been selected or if an
argument is out of range or omitted.
Program: ERROR
09. Arguments which follow a * command can only be read as an ASCII
string. If the string represents a number it has to be converted into
binary and stored in user memory before it can be used as a number.
Reading hexadecimal numerical arguments, checking their range and
validity, and converting them from an ASCII string into a binary
number will be explained and demonstrated in module 9.
Program: PEEK
10. The BBC Micro vectors can be altered to point to new routines in
either user memory or in sideways ram. When sideways ram or rom is
used for the new routines it is necessary to use extended rom vectors.
The use of extended rom vectors will be explained and demonstrated
with the conversion of a user memory cassette file locking routine
into sideways ram format.
Programs: VECTOR, LOCK
11. It is often necessary for sideways ram programs to use an area of
user memory as workspace. If the data stored in the workspace must not
be corrupted by other programs it is necessary to use private
workspace. Claiming private workspace will be explained and
demonstrated with an example program which reads the number of disc
cycles on the disc in the default drive.
Programs: PRIVATE, TRACE
12. Absolute workspace will only be of interest to the more
experienced user but a skeleton interpreter will be presented. The
absolute workspace service call (service call 1) is sent to every
active rom when the computer is switched on and when the Break key is
pressed. If all the registers are preserved service call 1 (or service
call &FE on the Master computer) can be used to provide a variety of
functions. This "illegal" use of service call 1 will be demonstrated
with a program which keeps the video interlace switched off.
Programs: ABSOL, INTLACE, TRACE
13. Errors created in other sideways roms can be trapped and acted
upon within your own sideways ram programs. Module 13 demonstrates how
the "Disc full" and "Cat full" errors generated by the DFS can be
trapped and used to prompt for a disc change. This is not a simple
task and uses most of the techniques described earlier in the course.
Programs: FILES, TRACE
14. When an interupt is generated by hardware in the computer system
and that interupt is not recognised by the MOS, it is first offered to
the paged roms and then to the user via the IRQ2 vector. Dealing with
unrecognised interupts will be dealt with in module 14 and illustrated
with a 15.75k SWR parallel printer buffer.
Program: BUFFER
15. All the earlier modules of the course that have used an
unrecognised * command interpreter have used a simple one-command
interpreter. A multiple command interpreter will be introduced,
explained and demonstrated in module 15. The multiple command
interpreter will accept commands shortened with a dot and prefixed
with an optional character.
Program: SOUNDS
16. When a multiple command interpreter is used in a SWR utility rom
it is easy to forget the syntax of all the new commands. It is often
useful for a SWR program to respond to the *HELP command by explaining
the syntax of its new commands. The multiple command interpreter
introduced in module 15 will be developed in module 16 to provide an
extended help service.
Programs: HELP, TRACE
17. All the rom images created in the earlier modules of the course
will be service rom images. Language roms are introduced in module 17
with the example language NOBASIC. Language rom design will be used
again when dealing with the RFS but it is simple enough to understand
and should be of interest in its own right.
Program: NOBASIC
18. The Rom Filing System is available on all BBC Microcomputers with
MOS 1.0, or later. In order to store files in the RFS they have to be
formatted with a block structure very similar to that used by the Tape
Filing System. The RFS will be introduced in module 18 with a simple
RFS interpreter and formatting program.
Programs: RFSHEAD, RFSGEN, DEMO, TRACE
19. The Disc Filing system can be booted with Ctrl+D+Break, the Tape
Filing system with Ctrl+Space+Break and the Network Filing System with
Ctrl+N+Break. You might expect the Rom Filing System to boot with
Ctrl+R+Break but it does not work. An interpreter which will boot the
RFS with Ctrl+R+Break will be demonstrated and explained in module 19.
Programs: BOOTRFS, RFSGEN, DEMO
20. Existing programs, in almost any BBC Microcomputer supported
language, can be run from the RFS with star commands without modifying
the existing program. This can be done with either a service or a
language rom design. Module 20 deals with the service rom design and
demonstrates how a BASIC program stored in the RFS can be run in user
memory with the new command *DEMO.
Programs: RFSGEN, RFSERV, DEMO
21. The language rom design can be used to run programs from the RFS
with a new * command. The language rom can be used in the highest
priority rom socket and selected as the default language when the
computer is switched on and when Ctrl+Break is pressed. This will be
demonstrated with a new language called RFS. The only function of this
language is to run a BASIC program in user memory.
Programs: RFSGEN, RFSLANG, DEMO
22. Rom cartridges should load and run a program from the cartridge
when the Break key is pressed. The RFS language rom design introduced
in module 21 can be modified to produce the format needed for rom
cartridges which will run BASIC and machine code programs in this way.
This technique uses an illegal interception of service call &FE and it
is not Tube compatible.
Programs: AUTORFS, RFSGEN, DEMO
23. All but one of the RFS roms in a computer should use the simple
interpreter introduced in module 18. Module 23 demonstrates a more
complex RFS header that only needs to be used in one of the RFS roms.
It includes extended help, auto-boot and running programs with a new *
command. Detailed instructions are included for novice BASIC
programmers.
Programs: ALLRFS, RFSGEN, RFSHEAD, DEMO
24. All the source code programs demonstrating the SWR techniques will
have HIMEM set to &3C00. This allows up to 16k of object code to be
held in memory in mode 7. The DFS sets PAGE to &1900 on the BBC B
leaving only 8.75k for the source code. Because of this it is
sometimes necessary to use modular programs with forward referencing
to overcome the memory limitations of the BBC Micro. These techniques
will be demonstrated in module 24.
Programs: MODONE, MODTWO, RFSGEN, DEMO
25. Index.
No programs.
When writing this course it was necessary to make some assumptions
about the readers who will use it to help them write their own
sideways ram software. The sideways rom/ram system has been widely
described and discussed in so many BBC Micro publications that it
seemed unnecessary to describe the basic concept in any detail. If you
don't know what sideways rom/ram is you are unlikely to want to, or to
be able to, write software to run in it.
I have assumed that you have programmed your BBC Micro in both BASIC
and Assembly language. If you do not understand programming in 6502
Assembly language using the BBC assembler you can expect to have some
difficulty with most of the course modules except perhaps modules 18
to 24 which deal with the RFS. Module 23 was written specifically for
BASIC programmers with absolutely no understanding of Assembly
language. If you have worked through a course in machine code
programming, such as the Telesoftware Osbits course, you should be
able to complete this course without any problems.
It seemed reasonable to assume that the readers with BBC B+ 128k and
Master series computers will have looked at the manuals provided with
their machines and already know how to load and use software in this
area of memory. Readers with BBC B and BBC B+ 64k micros will need to
make some modifications to the hardware of their machine and I will
give some advice on choosing a suitable upgrade. Instructions on
loading software into the sideways ram it provides will be supplied by
the manufacturer of the upgrade.
All the example programs have been written in BASIC 1 which lacks
the pseudo-opcodes to implement equate functions. These pseudo-opcodes
have been implemented in all the programs using BASIC functions. The
functions are called using, for example, OPT FNequb(&0D) as the
equivalent of the BASIC 2 EQUB &0D. The BASIC 1 assembler will not
accept a colon as part of a expression and so, for example, an
expression such as CMP #ASC(":") which is acceptable to BASIC 2 is
replaced with CMP #ASC("9")+1 which assembles identically and is
accepted by BASIC 1.
BASIC 1 does not implement remote assembly and so all references to
absolute addresses have had the difference between the address at
which they run (&8000) and the address at which they are assembled
(&3C00) added to that address. All references to absolute addresses,
for example subroutine in JSR subroutine, have been replaced with the
remote equivalent JSR subroutine+diff. The constant diff has been
assigned the value of &8000-&3C00 in all the programs that use it.
All the programs used to illustrate the course could be used by a
non-programmer to build a sideways ram library without understanding
why the programs work but the real objective of the course is to teach
programmers how to create their own software and not how to use the
examples provided.
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*
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00000440 0d 50 72 6f 67 72 61 6d 20 6e 61 6d 65 3a 20 20 |.Program name: |
00000450 20 20 20 55 73 65 64 20 69 6e 20 6d 6f 64 75 6c | Used in modul|
00000460 65 73 3a 0d 0d 41 42 53 4f 4c 20 20 20 20 20 20 |es:..ABSOL |
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00000680 20 20 20 20 20 20 20 20 20 20 20 20 20 20 31 30 | 10|
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000006b0 44 4f 4e 45 20 20 20 20 20 20 20 20 20 20 20 20 |DONE |
000006c0 32 34 20 20 20 20 4d 6f 64 75 6c 61 72 20 70 72 |24 Modular pr|
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000006e0 20 20 20 20 20 20 20 20 20 20 20 20 32 34 20 20 | 24 |
000006f0 20 20 4d 6f 64 75 6c 61 72 20 70 72 6f 67 72 61 | Modular progra|
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00000740 49 43 20 20 20 20 20 20 20 20 20 20 20 31 37 20 |IC 17 |
00000750 20 20 20 4c 61 6e 67 75 61 67 65 20 72 6f 6d 20 | Language rom |
00000760 64 65 73 69 67 6e 0d 4f 53 42 59 54 45 20 20 20 |design.OSBYTE |
00000770 20 20 20 20 20 20 20 20 20 30 36 20 20 20 20 55 | 06 U|
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000007a0 20 20 20 20 20 30 37 20 20 20 20 4f 73 77 6f 72 | 07 Oswor|
000007b0 64 20 64 65 6d 6f 6e 73 74 72 61 74 69 6f 6e 0d |d demonstration.|
000007c0 4f 53 57 4f 52 44 20 20 20 20 20 20 20 20 20 20 |OSWORD |
000007d0 20 20 30 37 20 20 20 20 55 6e 72 65 63 6f 67 6e | 07 Unrecogn|
000007e0 69 73 65 64 20 4f 73 77 6f 72 64 0d 50 45 45 4b |ised Osword.PEEK|
000007f0 20 20 20 20 20 20 20 20 20 20 20 20 20 20 30 39 | 09|
00000800 20 20 20 20 52 65 61 64 69 6e 67 20 6e 75 6d 65 | Reading nume|
00000810 72 69 63 61 6c 20 61 72 67 75 6d 65 6e 74 73 0d |rical arguments.|
00000820 50 52 49 56 41 54 45 20 20 20 20 20 20 20 20 20 |PRIVATE |
00000830 20 20 31 31 20 20 20 20 50 72 69 76 61 74 65 20 | 11 Private |
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00000850 4d 20 20 20 20 20 20 20 20 20 20 20 41 6c 6c 20 |M All |
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00002450 6d 73 3a 20 48 45 4c 50 2c 20 54 52 41 43 45 0d |ms: HELP, TRACE.|
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000024c0 20 4c 61 6e 67 75 61 67 65 20 72 6f 6d 73 20 61 | Language roms a|
000024d0 72 65 20 69 6e 74 72 6f 64 75 63 65 64 20 69 6e |re introduced in|
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000027f0 74 72 6c 2b 52 2b 42 72 65 61 6b 20 62 75 74 20 |trl+R+Break but |
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00003c4d 
17_10_87/B\SWR00.m0
17_10_87/B\SWR00.m1
17_10_87/B\SWR00.m2
17_10_87/B\SWR00.m4
17_10_87/B\SWR00.m5
.