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24-06-88/T\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 » telesoftware7.adl
Filename: 24-06-88/T\SWR00
Read OK:
File size: 3C4D bytes
Load address: 0000
Exec address: FFFFFFFF
Duplicates

There is 1 duplicate copy of this file in the archive:

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.
00000000  4d 61 73 74 65 72 69 6e  67 20 53 69 64 65 77 61  |Mastering Sidewa|
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00000020  6f 64 75 6c 65 20 30 30  20 2d 20 50 72 65 66 61  |odule 00 - Prefa|
00000030  63 65 0d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |ce.-------------|
00000040  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----------------|
*
00000060  2d 2d 2d 2d 2d 0d 0d 20  20 54 68 69 73 20 63 6f  |-----..  This co|
00000070  75 72 73 65 20 68 61 73  20 62 65 65 6e 20 64 65  |urse has been de|
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000000a0  74 65 72 20 75 73 65 72  73 0d 77 69 74 68 20 73  |ter users.with s|
000000b0  75 66 66 69 63 69 65 6e  74 20 6b 6e 6f 77 6c 65  |ufficient knowle|
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000000d0  63 65 20 74 6f 20 77 72  69 74 65 20 73 6f 66 74  |ce to write soft|
000000e0  77 61 72 65 20 66 6f 72  0d 73 69 64 65 77 61 79  |ware for.sideway|
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00000110  20 6f 77 6e 20 65 78 69  73 74 69 6e 67 20 70 72  | own existing pr|
00000120  6f 67 72 61 6d 73 2c 20  69 6e 20 61 6e 79 0d 42  |ograms, in any.B|
00000130  42 43 20 4d 69 63 72 6f  20 73 75 70 70 6f 72 74  |BC Micro support|
00000140  65 64 20 6c 61 6e 67 75  61 67 65 2c 20 74 6f 20  |ed language, to |
00000150  72 75 6e 20 66 72 6f 6d  20 74 68 65 20 52 6f 6d  |run from the Rom|
00000160  20 46 69 6c 69 6e 67 20  53 79 73 74 65 6d 20 28  | Filing System (|
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000001f0  68 65 20 6f 62 6a 65 63  74 0d 63 6f 64 65 20 74  |he object.code t|
00000200  6f 20 62 65 20 6c 6f 61  64 65 64 20 69 6e 74 6f  |o be loaded into|
00000210  20 53 57 52 2e 0d 0d 20  54 68 65 20 65 78 61 6d  | SWR... The exam|
00000220  70 6c 65 20 70 72 6f 67  72 61 6d 73 20 63 61 6e  |ple programs can|
00000230  20 61 6c 6c 20 62 65 20  73 61 76 65 64 20 6f 6e  | all be saved on|
00000240  74 6f 20 6f 6e 65 20 73  69 64 65 20 6f 66 20 61  |to one side of a|
00000250  20 31 30 30 6b 20 64 69  73 63 2e 0d 41 6c 6c 20  | 100k disc..All |
00000260  74 68 65 20 70 72 6f 67  72 61 6d 73 20 61 72 65  |the programs are|
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00000370  61 63 74 20 63 6f 6d 70  75 74 65 72 73 20 77 69  |act computers wi|
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000003b0  6c 6c 20 61 6c 73 6f 20  72 75 6e 20 6f 6e 20 74  |ll also run on t|
000003c0  68 65 20 41 63 6f 72 6e  20 45 6c 65 63 74 72 6f  |he Acorn Electro|
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00000410  73 65 2e 0d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |se..------------|
00000420  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----------------|
00000430  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 0d  |---------------.|
00000440  0d 50 72 6f 67 72 61 6d  20 6e 61 6d 65 3a 20 20  |.Program name:  |
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00000530  52 53 4f 52 20 20 20 20  20 20 20 20 20 20 20 20  |RSOR            |
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00000560  20 20 20 20 20 20 20 20  20 20 31 38 2d 32 34 20  |          18-24 |
00000570  41 6c 6c 20 52 46 53 20  6d 6f 64 75 6c 65 73 0d  |All RFS modules.|
00000580  45 4e 41 42 4c 45 20 20  20 20 20 20 20 20 20 20  |ENABLE          |
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000005b0  54 53 54 20 20 20 20 20  20 20 20 20 20 20 30 34  |TST           04|
000005c0  20 20 20 20 44 65 6d 6f  6e 73 74 72 61 74 65 20  |    Demonstrate |
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00000610  20 20 20 20 20 20 20 20  20 31 33 20 20 20 20 54  |         13    T|
00000620  72 61 70 70 69 6e 67 20  65 72 72 6f 72 73 0d 48  |rapping errors.H|
00000630  45 4c 50 20 20 20 20 20  20 20 20 20 20 20 20 20  |ELP             |
00000640  20 31 36 20 20 20 20 45  78 74 65 6e 64 65 64 20  | 16    Extended |
00000650  68 65 6c 70 0d 49 4e 54  4c 41 43 45 20 20 20 20  |help.INTLACE    |
00000660  20 20 20 20 20 20 20 31  32 20 20 20 20 53 65 72  |       12    Ser|
00000670  76 69 63 65 20 63 6f 64  65 20 31 0d 4c 4f 43 4b  |vice code 1.LOCK|
00000680  20 20 20 20 20 20 20 20  20 20 20 20 20 20 31 30  |              10|
00000690  20 20 20 20 50 72 6f 67  72 61 6d 20 74 6f 20 63  |    Program to c|
000006a0  6f 6e 76 65 72 74 20 74  6f 20 53 57 52 0d 4d 4f  |onvert to SWR.MO|
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|
000006d0  6f 67 72 61 6d 6d 69 6e  67 0d 4d 4f 44 54 57 4f  |ogramming.MODTWO|
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|
00000700  6d 6d 69 6e 67 0d 4e 45  57 43 4f 4d 20 20 20 20  |mming.NEWCOM    |
00000710  20 20 20 20 20 20 20 20  30 33 20 20 20 20 53 69  |        03    Si|
00000720  6d 70 6c 65 20 2a 20 63  6f 6d 6d 61 6e 64 20 69  |mple * command i|
00000730  6e 74 65 72 70 72 65 74  65 72 0d 4e 4f 42 41 53  |nterpreter.NOBAS|
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   |
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