Z80 on a BBC B

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KayjayUK
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Z80 on a BBC B

Postby KayjayUK » Tue Oct 17, 2017 5:32 am

Hi everyone, I'm new on Stardot and a new returnee to the Beeb since retiring.

I originally cut my computer teeth on a Nascom 1 and 2 in the 70's when they came out and consequently got hooked on Z80 assembler. I then went on to buy a Beeb B when they were released in the 80's and went through the whole learning curve again, programming in assembler using Romas, a wonderful cross assembler on ROM from W.E.

Now my question is this, I would like to use my Beeb as a Z80 machine, writing software in Z80 assembler, hopefully with Romas rather than BeebBasic and of course running the software once written on the Beeb. Is this possible ? Obviously I will need a Z80 copro, probably Torch as the cheese wedges don't appear very often for sale .... Gawd I wish I hadn't sold my cheese wedge but at the time I desperately needed funds something that is no longer a problem since retiring.

So, can anyone offer me any advice on how to go about this or even if it's possible to just use the Beeb as a dedicated Z80 machine.

Thanks guys....Keith
From little Acorns great Beebs grow!

duikkie
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Re: Z80 on a BBC B

Postby duikkie » Tue Oct 17, 2017 5:40 am

meta assembler ?

KayjayUK wrote:Hi everyone, I'm new on Stardot and a new returnee to the Beeb since retiring.

I originally cut my computer teeth on a Nascom 1 and 2 in the 70's when they came out and consequently got hooked on Z80 assembler. I then went on to buy a Beeb B when they were released in the 80's and went through the whole learning curve again, programming in assembler using Romas, a wonderful cross assembler on ROM from W.E.

Now my question is this, I would like to use my Beeb as a Z80 machine, writing software in Z80 assembler, hopefully with Romas rather than BeebBasic and of course running the software once written on the Beeb. Is this possible ? Obviously I will need a Z80 copro, probably Torch as the cheese wedges don't appear very often for sale .... Gawd I wish I hadn't sold my cheese wedge but at the time I desperately needed funds something that is no longer a problem since retiring.

So, can anyone offer me any advice on how to go about this or even if it's possible to just use the Beeb as a dedicated Z80 machine.

Thanks guys....Keith

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jonb
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Re: Z80 on a BBC B

Postby jonb » Tue Oct 17, 2017 5:51 am

Hi KayJay and welcome to StartDot!

To answer your question... the BBC is a 6502 machine, as I am sure you know. If you want to use it for Z80 coding you will need a Z80 co-processor.

Probably the easiest/cheapest way to achieve this is to get one of Hoglet's matchbox co-processors. It is discussed at great length here: http://www.stardot.org.uk/forums/viewto ... =44&t=8852

It's a tiny board that plugs directly into the Tube connector on the underside of the Beeb. Very neat, no unsightly cables. You can set it up as a Z80 co-processor and run Z80 BBC Basic on it along with many other programs and utilities (which I assume exist - I don't have much actual experience of using it, even though I have one) including Acorn CP/M. It can also act as a 6502 or 6809 co-processor.

I would be very surprised if WE ROMAS could assemble Z80 code. Sounds like a sideways ROM for native 6502 assembly - so I expect you will be looking for a Z80 assembler. There should be one built into Z80 BBC basic, but if you really get into it you will probably be better off using a PC to edit and assemble, then run it on the BBC (on the Z80 co-processor).

This is what I use:
  • Notepad++ (text editor)
  • 64 bit version of TASM (assembler) as I run 64 bit Windows 10
  • TeraTerm (terminal emulator / serial transfer program) to get the assembled program onto the target machine (for me, usually a CP/M machine running Kermit) via serial.

Cheers
JonB

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danielj
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Re: Z80 on a BBC B

Postby danielj » Tue Oct 17, 2017 6:19 am

Welcome!
Matchbox copros aren't available anymore, so unless you can find someone willing to part with one, that door is unfortunately closed :(

Instead you have a few options:
Cheesewedge Z80 (expensive)
Torch Communicator (£40-50ish, come up on ebay from time to time).
Pi-Zero copro (needs a level shifter from Kjell, probably the cheapest and most flexible option but is a software emulation rather than hardware, some people don't like that)
De-0 nano (relatively expensive) with tube silencer and Z80 FPGA Design from John Kortink: http://www.zeridajh.org/hardware/softz8 ... /index.htm

d.

KayjayUK
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Re: Z80 on a BBC B

Postby KayjayUK » Tue Oct 17, 2017 6:29 am

Edit - I was typing this post while the one above appeared. Anyway, it's answered my question on byying one !

Thanks for the info Jon.

Romas will assemble Z80, it has a disc supplied with it containig routines to enable assembling of several different processors, I have successfully written and assembled Z80 on it back in the 80's and then transferred it to a dedicated device, a car ignition ecu I built for a friend grass track racer.

The matchbox looks brilliant, I assume that the code is now stable or at least the Z80 side of it, I would like to be able to run Romas if I can but if not maybe there is another assembler other than using the pseudo assemblers in the Basic rom. I don't know why but I have an aversion to BASIC, it's like programming for toddlers to me :-)

Anyway, thanks for the info, I'm very grateful to you. How do I get hold of one of the matchbox boards?

Keith
From little Acorns great Beebs grow!

KayjayUK
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Re: Z80 on a BBC B

Postby KayjayUK » Tue Oct 17, 2017 6:40 am

Ok, so I'm back to my original thoughts of obtaining a Torch.

Would I be able to use Romas which is written in 6502 whilst accessing the Torch? What I mean is can I use Romas to edit and assemble my Z80 code on the Torch given that it is written in 6502 and resident in the Beebs rom sockets.

Sorry if these questions sounds infantile, I've no experience of this whatsoever so I'm totally blind on the subject.

Cheers ...Keith
From little Acorns great Beebs grow!

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BigEd
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Re: Z80 on a BBC B

Postby BigEd » Tue Oct 17, 2017 6:43 am

(These days I'd recommend the pi-based solution for cost, availability, and convenience in updating:
https://github.com/hoglet67/PiTubeDirec ... er-options
It's true that there's no physical Z80 chip in there. But it's a piece of hardware you plug into your Beeb and it runs exactly like a Z80.)

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danielj
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Re: Z80 on a BBC B

Postby danielj » Tue Oct 17, 2017 6:44 am

Not in the slightest! The whole point of this forum is to share knowledge :)

d.

RobC
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Re: Z80 on a BBC B

Postby RobC » Tue Oct 17, 2017 7:06 am

I'd also vote for a Pi co-pro.

Not only is it the cheapest option but, alongside access to super-fast Z80 and 6502 co-pros, you get a 6809, ARM, 32016, 80286 and the 1GHz (!) native Pi ARM. And you can switch between them all with a *FX command.

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1024MAK
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Re: Z80 on a BBC B

Postby 1024MAK » Tue Oct 17, 2017 7:15 am

The Torch is slightly different as it does not do things in the same way as the Acorn second processor systems.

With the Acorn second processor systems, when the OS in the BBC Micro detects the ROM in the BBC, that ROM then checks for a second processor, it can then "transfer" control to the second processor. The BBC then becomes an IO system. It waits for commands from the second processor, acts on them, and returns / transfers data across the Tube (which interconnects them). This is of course a very much simplified description.

A 6502 coded ROM in the Beeb would be recognised as 6502 code and would not be transferred to a Z80 second processor. And of course as it is not Z80, it would not run anyway.

If Acorns system is not used, then it is possible to do your own thing. Elite does this.
There is no reason why it can't be the other way round, with the Beeb being the master and the second processor being a slave.
Then the assembler could run on the Beeb. Your own ROM could then transfer the Z80 code to the Z80 second processor and run it.

Mark
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vanpeebles
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Re: Z80 on a BBC B

Postby vanpeebles » Tue Oct 17, 2017 7:23 am

I have a Torch disk unit and rom I'd be happy to sell. The torch z80 card is missing but they are available new on ebay.

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Lardo Boffin
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Re: Z80 on a BBC B

Postby Lardo Boffin » Tue Oct 17, 2017 8:06 am

With reference to the Z80 BBC BASIC it is used merely as a shell to hold the assembly in this context - there are a couple of lines of BASIC and the everything else is Z80. When you run the program it assembles the Z80 machine code and you can run that. The Acorn system does also offer a CPM assembler.

Below are a couple of quick photos from the Z80 BBC BASIC reference book:-


931100E1-B56C-4856-ACA9-0E13C6D6525D.jpeg



8E0DC59B-FC6C-4EE5-BE05-D14F58233D49.jpeg


A54A0B98-3F7F-4669-B756-AAC41481F409.jpeg


I would imagine all of these books are scanned and online? Well worth a quick look to see what Acornsoft offered with their Z80.
BBC model B 32k issue 4, 16k sideways RAM, Watford 12 ROM board, Retroclinic Datacentre + HDD, matchbox co-proc, Viglen twin 40/80 5.25" discs, acorn cassette
BBC model B 32k issue 7, turboMMC, Opus Challenger 3 512k, Pi 3 coproc, Acorn 6502 coproc

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jonb
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Re: Z80 on a BBC B

Postby jonb » Tue Oct 17, 2017 8:24 am

danielj wrote:Not in the slightest! The whole point of this forum is to share knowledge :)

d.


Hear, hear!

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Lardo Boffin
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Re: Z80 on a BBC B

Postby Lardo Boffin » Tue Oct 17, 2017 8:37 am

Here is a link to the Acorn Z80 discs thanks to JGH

http://mdfs.net/Software/Tube/Z80/

Edit and a link to a couple of the manuals

http://www.primrosebank.net/computers/b ... anuals.htm
BBC model B 32k issue 4, 16k sideways RAM, Watford 12 ROM board, Retroclinic Datacentre + HDD, matchbox co-proc, Viglen twin 40/80 5.25" discs, acorn cassette
BBC model B 32k issue 7, turboMMC, Opus Challenger 3 512k, Pi 3 coproc, Acorn 6502 coproc

KayjayUK
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Re: Z80 on a BBC B

Postby KayjayUK » Tue Oct 17, 2017 8:43 am

vanpeebles wrote:I have a Torch disk unit and rom I'd be happy to sell. The torch z80 card is missing but they are available new on ebay.

Is the disk unit necessary for the Z80 card ? Aren't they just another make of standard drives? Obviously the rom is but I ask because I already have drives. If they aren't needed by the Torch then I can get an image online and blow a rom.

Thanks anyway, incidentally, what are the drives 40/80 DS or other? I may still be interested. Let me know this info and I'll pm you if I want to go further.

Thanks again, I appreciate your input.

Keith
From little Acorns great Beebs grow!

KayjayUK
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Re: Z80 on a BBC B

Postby KayjayUK » Tue Oct 17, 2017 8:45 am

1024MAK wrote:The Torch is slightly different as it does not do things in the same way as the Acorn second processor systems.

With the Acorn second processor systems, when the OS in the BBC Micro detects the ROM in the BBC, that ROM then checks for a second processor, it can then "transfer" control to the second processor. The BBC then becomes an IO system. It waits for commands from the second processor, acts on them, and returns / transfers data across the Tube (which interconnects them). This is of course a very much simplified description.

A 6502 coded ROM in the Beeb would be recognised as 6502 code and would not be transferred to a Z80 second processor. And of course as it is not Z80, it would not run anyway.

If Acorns system is not used, then it is possible to do your own thing. Elite does this.
There is no reason why it can't be the other way round, with the Beeb being the master and the second processor being a slave.
Then the assembler could run on the Beeb. You own ROM could then transfer the Z80 code to the Z80 second processor and run it.

Mark


Now this sounds like what I'm looking for, make the beeb the master and I'm winning ! Thanks Mark, you're a star.

Keith
From little Acorns great Beebs grow!

KayjayUK
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Re: Z80 on a BBC B

Postby KayjayUK » Tue Oct 17, 2017 8:46 am

Lardo Boffin wrote:Here is a link to the Acorn Z80 discs thanks to JGH

http://mdfs.net/Software/Tube/Z80/

Edit and a link to a couple of the manuals

http://www.primrosebank.net/computers/b ... anuals.htm



Thanks Lardo, I will peruse the info.

Keith
From little Acorns great Beebs grow!

KayjayUK
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Re: Z80 on a BBC B

Postby KayjayUK » Tue Oct 17, 2017 8:52 am

Wow !!! You guys are amazing, I cannot thank you all enough. Each one of you has suggested a different solution each which has positives. I just need to think deeply about how to implement this. At the moment I'm liking Marks suggestion of the Torch card and putting the beeb in control of the copro but even so the others all look amazing too!

Thank you to each and every one of you, you are truly enthusiasts who are prepared to offer all their long learnt knowledge. Superb ! I'm overawed, can you tell :D

Keith
From little Acorns great Beebs grow!

KayjayUK
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Re: Z80 on a BBC B

Postby KayjayUK » Tue Oct 17, 2017 8:56 am

1024MAK wrote:The Torch is slightly different as it does not do things in the same way as the Acorn second processor systems.

With the Acorn second processor systems, when the OS in the BBC Micro detects the ROM in the BBC, that ROM then checks for a second processor, it can then "transfer" control to the second processor. The BBC then becomes an IO system. It waits for commands from the second processor, acts on them, and returns / transfers data across the Tube (which interconnects them). This is of course a very much simplified description.

A 6502 coded ROM in the Beeb would be recognised as 6502 code and would not be transferred to a Z80 second processor. And of course as it is not Z80, it would not run anyway.

If Acorns system is not used, then it is possible to do your own thing. Elite does this.
There is no reason why it can't be the other way round, with the Beeb being the master and the second processor being a slave.
Then the assembler could run on the Beeb. You own ROM could then transfer the Z80 code to the Z80 second processor and run it.

Mark


Another thought Mark, does it have to be the cheese wedge to makethebeeb the master or is that facility available on the Torch too ?

Keith
From little Acorns great Beebs grow!

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vanpeebles
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Re: Z80 on a BBC B

Postby vanpeebles » Tue Oct 17, 2017 9:02 am

I think they are just normal drives but part of the torch z80 set up. They are not switchable either :(

Image

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danielj
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Re: Z80 on a BBC B

Postby danielj » Tue Oct 17, 2017 9:09 am

Hi Keith - you don't need the Torch disk pack to run the communicator - it's just a double disk drive. You can use whatever's convenient! But you will obviously need a disc solution of some description :)

d.

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Lardo Boffin
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Re: Z80 on a BBC B

Postby Lardo Boffin » Tue Oct 17, 2017 9:22 am

I’m pretty sure for the Acorn Z80 you need a double disc setup which is 80 track double sided. These four Beeb discs then equate to two CPM discs.
BBC model B 32k issue 4, 16k sideways RAM, Watford 12 ROM board, Retroclinic Datacentre + HDD, matchbox co-proc, Viglen twin 40/80 5.25" discs, acorn cassette
BBC model B 32k issue 7, turboMMC, Opus Challenger 3 512k, Pi 3 coproc, Acorn 6502 coproc

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jonb
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Re: Z80 on a BBC B

Postby jonb » Tue Oct 17, 2017 9:25 am

..and would you like to document your findings here, Keith?

I ask because I would like to run Acorn CP/M on my co-pro but am not sure how to do it (most likely because I've not tried yet!). I did ask a while back if the Turbo MMC could be used as a HDD for the CP/M system - that'd be very useful - or as a floppy.. so if you found a way that'd be pretty brill!

Cheers
JonB

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Lardo Boffin
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Re: Z80 on a BBC B

Postby Lardo Boffin » Tue Oct 17, 2017 10:17 am

This is all of the manuals for the acornsoft z80.

81515C28-AF5A-4F55-9148-4F088CE09CFD.jpeg


It looks like most of them have not been scanned. Certainly I could only find a couple after some googleing.

To make use of the Z80 properly I suspect that the CPM2.2 with GSX graphics needs scanning. It’s a big book...

Any volunteers? Am happy to send it to someone to do but I have no time myself for the next few months.
BBC model B 32k issue 4, 16k sideways RAM, Watford 12 ROM board, Retroclinic Datacentre + HDD, matchbox co-proc, Viglen twin 40/80 5.25" discs, acorn cassette
BBC model B 32k issue 7, turboMMC, Opus Challenger 3 512k, Pi 3 coproc, Acorn 6502 coproc

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Lardo Boffin
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Re: Z80 on a BBC B

Postby Lardo Boffin » Tue Oct 17, 2017 10:19 am

With the User Guide for scale!

65D7B450-A835-42F1-BBEA-6DC7C4CBB7BC.jpeg
BBC model B 32k issue 4, 16k sideways RAM, Watford 12 ROM board, Retroclinic Datacentre + HDD, matchbox co-proc, Viglen twin 40/80 5.25" discs, acorn cassette
BBC model B 32k issue 7, turboMMC, Opus Challenger 3 512k, Pi 3 coproc, Acorn 6502 coproc

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Lardo Boffin
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Re: Z80 on a BBC B

Postby Lardo Boffin » Tue Oct 17, 2017 10:37 am

jonb wrote:..and would you like to document your findings here, Keith?

I ask because I would like to run Acorn CP/M on my co-pro but am not sure how to do it (most likely because I've not tried yet!). I did ask a while back if the Turbo MMC could be used as a HDD for the CP/M system - that'd be very useful - or as a floppy.. so if you found a way that'd be pretty brill!

Cheers
JonB


Hi Jon

I had the Z80 stuff set up on my TurboMMC (currently that beeb is being mothballed as we are trying to move house) so attached is the latest backup I can find of the MMB file - I had a separate SD card for 6502 and Z80. It has the CPM discs split into the appropriate drive numbers used as floppies. Its been a long while since I looked at any of it though...
Attachments
BEEB20161021.zip
Z80 MMB
(2.28 MiB) Downloaded 7 times
BBC model B 32k issue 4, 16k sideways RAM, Watford 12 ROM board, Retroclinic Datacentre + HDD, matchbox co-proc, Viglen twin 40/80 5.25" discs, acorn cassette
BBC model B 32k issue 7, turboMMC, Opus Challenger 3 512k, Pi 3 coproc, Acorn 6502 coproc

KayjayUK
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Re: Z80 on a BBC B

Postby KayjayUK » Tue Oct 17, 2017 11:05 am

jonb wrote:..and would you like to document your findings here, Keith?

I ask because I would like to run Acorn CP/M on my co-pro but am not sure how to do it (most likely because I've not tried yet!). I did ask a while back if the Turbo MMC could be used as a HDD for the CP/M system - that'd be very useful - or as a floppy.. so if you found a way that'd be pretty brill!

Cheers
JonB


I will certainly try, it's the least I can do after so much help.

Keith
From little Acorns great Beebs grow!

KayjayUK
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Re: Z80 on a BBC B

Postby KayjayUK » Tue Oct 17, 2017 11:09 am

jonb wrote:..and would you like to document your findings here, Keith?

I ask because I would like to run Acorn CP/M on my co-pro but am not sure how to do it (most likely because I've not tried yet!). I did ask a while back if the Turbo MMC could be used as a HDD for the CP/M system - that'd be very useful - or as a floppy.. so if you found a way that'd be pretty brill!

Cheers
JonB



Can you use the Datacentre? I has 2 drives on it doesn't ? I'm still waiting for mine to arrive, think it'll be tomorrow.

Keith
From little Acorns great Beebs grow!

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Lardo Boffin
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Re: Z80 on a BBC B

Postby Lardo Boffin » Tue Oct 17, 2017 11:11 am

I had problems using mine I think but they may have been resolved since. I will try to track down the appropriate thread but may take a while!
Awesome bit of kit though.

Edit - I had troubles copying files from the datacentre drives to the optional HDD as below: -

viewtopic.php?f=3&t=11875&hilit=cpm

So if you don't have the CF HDD you should be OK! If you do you may have to stick with using the datacentre drives only and remembering to back up your work before switching off...
Last edited by Lardo Boffin on Tue Oct 17, 2017 12:10 pm, edited 1 time in total.
BBC model B 32k issue 4, 16k sideways RAM, Watford 12 ROM board, Retroclinic Datacentre + HDD, matchbox co-proc, Viglen twin 40/80 5.25" discs, acorn cassette
BBC model B 32k issue 7, turboMMC, Opus Challenger 3 512k, Pi 3 coproc, Acorn 6502 coproc

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1024MAK
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Re: Z80 on a BBC B

Postby 1024MAK » Tue Oct 17, 2017 12:09 pm

KayjayUK wrote:
1024MAK wrote:The Torch is slightly different as it does not do things in the same way as the Acorn second processor systems.

With the Acorn second processor systems, when the OS in the BBC Micro detects the ROM in the BBC, that ROM then checks for a second processor, it can then "transfer" control to the second processor. The BBC then becomes an IO system. It waits for commands from the second processor, acts on them, and returns / transfers data across the Tube (which interconnects them). This is of course a very much simplified description.

A 6502 coded ROM in the Beeb would be recognised as 6502 code and would not be transferred to a Z80 second processor. And of course as it is not Z80, it would not run anyway.

If Acorns system is not used, then it is possible to do your own thing. Elite does this.
There is no reason why it can't be the other way round, with the Beeb being the master and the second processor being a slave.
Then the assembler could run on the Beeb. You own ROM could then transfer the Z80 code to the Z80 second processor and run it.

Mark


Another thought Mark, does it have to be the cheese wedge to makethebeeb the master or is that facility available on the Torch too ?

Keith

Keep in mind that what I described is something that would be possible if someone wrote the code to do it. As far as I know, such a system has not been found in the wild.

The main reason for the Z80 second processors (both Torch and Acorn) was to enable the Beeb to run CP/M applications. Of course, the 'easy' way is to write the code on the Beeb with the second processor disabled. Then save it to disk. Reboot the Beeb with the second processor enabled, then load the code onto the second processor and run it. But both systems need to be able to understand the same disk filing system.

Are there any members who have tried this?

The hardware part of the Acorn Tube interface, that is a part of every Acorn second processor, uses a special chip (a custom ULA) to enable the Beeb CPU to be able to communicate with the second processor CPU. This chip has various registers some of which are FIFO, some being multiple bytes deep.

The Torch system instead uses a 6522 VIA connected 'back-to-back' to a 8255 PIO. By this I mean that the general purpose I/O pins on the 6522 VIA are connected to the general purpose I/O pins on the 8255 PIO. So the 6502 in the Beeb can write to the 6522. Then the Z80 on board can read the same data byte from the 8255. And of course, the reverse works as well. At power-up and at reset, the Z80 runs a simple program from ROM, this copies itself into RAM. It then switches out the ROM leaving just the 64k bytes of RAM accessible to the Z80. Now that it is running in RAM, the program waits for a data transfer from the Beeb.

Because of the different hardware, the software on the ROM in the Beeb and on the Torch second processor are different to the Acorn system, but the principles are similar. The Torch system as intended runs CP/N, which is version of CP/M. But there is no reason why someone who knows 6502 and Z80 code can't write and use their own system.

A picture of the Torch Z80 second processor board is here:
Image
http://blog.tynemouthsoftware.co.uk/2013/10/z80-cpm-single-board-computer.html

This page describes the Torch system

Mark
For a "Complete BBC Games Archive" visit www.bbcmicro.co.uk NOW!
BeebWiki‬ - for answers to many questions...


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