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Old 23rd Aug 2011, 8:59 am   #1
Alf Fisher
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Default Maplin Z80 SBC

Hi everyone,
Back in the early 90s, Maplin produced a single board Z80 based computer GB86. Does anyone have a copy of the monitor code or any similar monitor that will fit in a 2716 EPROM? I think it was originally written by Graham Dixey who also wrote a whole series on programming the Z80.
Any help appreciated and thanks for your time.

Alf
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Old 23rd Aug 2011, 12:44 pm   #2
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Default Re: Maplin Z80 SBC

It's a long time ago now but, from memory, 8080 code would be compatible at the machine-code level and therefore might widen your choice. The name Scelbi seems to be nagging at me though I haven't Googled it.

I also remember some Tiny Basics that ought to fit in a 2716.

Do you know the memory map and I/O map of the target hardware?
Graham
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Old 24th Aug 2011, 8:41 pm   #3
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Default Re: Maplin Z80 SBC

OK, here:

http://www.hartetechnologies.com/manuals/Scelbi/

Graham
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Old 28th Aug 2011, 8:00 pm   #4
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Default Re: Maplin Z80 SBC

Hi Graham,
I have dredged my way through the www and found the Scelbi docs after you mentioned it in your first reply but I've been away on a long weekend and just got back so haven't done anything with it as yet. I know the details of the address & I/O maps.
I thought a good first step would be to write some code to check the hardware works. Alas nobody seems to have heard of the Maplin boards so far.
Regards,
Alf
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Old 29th Aug 2011, 10:35 am   #5
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Default Re: Maplin Z80 SBC

Hi Alf,
This could save you a lot of typing:

I've just found the 8080 board that I did my computer science project on. It has its monitor program on two 8708s (= 1 x 2716 !) so apart from modifying some addresses it ought to run on your Z80.

I could lend (by post) the chips to you and hunt for the documentation...

Ideally of course I'd off-load the contents and email that but I can't think of a straightforward way to do that just now.

Graham
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Old 30th Aug 2011, 10:33 am   #6
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Default Re: Maplin Z80 SBC

HI: Alf,this may also help,in the conversion.
This conversion table is from the Nascom -1 Z80 based computer.Gezza
Attached Files
File Type: pdf 8080 to z80 p1.pdf (428.6 KB, 410 views)
File Type: pdf 8080 to z80 p2.pdf (478.2 KB, 267 views)
File Type: pdf 8080 to z80.pdf (215.6 KB, 236 views)
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Old 2nd Sep 2011, 5:44 pm   #7
Alf Fisher
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Default Re: Maplin Z80 SBC

Hi Gezza,
Thanks for your posting with the pdfs. I am collecting quite a lot of Z80 based articles etc and have found a number of operating systems on the web such as ZAP and BBug. You mention Nascom and I find there is still a large following for these good old bits of kit. I used to have a Nascom in the early 80s so when I found the NASBUG4 monitor, I decided to use a modified version of that.
Since my last posting, I wrote a simple bit of code to test and prove the board hardware. Its just as well I did as there was a problem and I had to replace the reset electrolytic. The circuit shows 100uF but when I built it some time ago, I thought that was a bit large so I put in a 10uF and now there is a 1uF. I also put a larger value and physically bigger (220uF) to replace the tiny little 100uF that was there on the 5volt line. Then I concluded the program was looping and waiting for something that was never going to happen. I then changed to code to test the correct bit in the USART status register, and it worked. All I need now is to complete the programming exercise for my application. Many thanks for your input and help.

Regards,
Alf
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Old 2nd Sep 2011, 8:03 pm   #8
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Default Re: Maplin Z80 SBC

HI.Alf.
You seem to have got it now. I have not looked at a Nascom since about 1981 ,I built my own and then gave it to a friend who I think still has a few of them,unfortunatly I have lost his address ,would like to know how he is doing these day's.Have looked at some Nascom sites but still not there.
We used to have clubs in them day's and I was the first to get 2400 baud rate on the Nascom with a few components ,the only problem was no one else could use my software but I could still use theirs and that made everyone excited in 1979. Don't know what happened to the circuit data unless I gave it to him.
Anyway BOT. I forgot it all now and was intrieged that some body else was interested in the Nascom .I also have a circuit for a 33 and 390 Teleprinter to go on parallel input-output use.
I did think that someone on here wanted something of that sort but can not find him so if he see's this thread he may well come back ,and I will try and put it on the forum.
So here is my question to you Alf do you have any of the following books,
1-MostekZ80 MK3881 Parallel I/O Controller
1-MK 3880 Central Processing Unit
1-Z80 Programming Manual
1-NASBUG-4 Monitor Software Manual inc Circuit.
1-NASCOM-1 Programming Manual.Gezza
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Old 3rd Sep 2011, 6:58 pm   #9
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Default Re: Maplin Z80 SBC

Quote:
Originally Posted by Alf Fisher View Post
Hi everyone,
Back in the early 90s, Maplin produced a single board Z80 based computer GB86. Does anyone have a copy of the monitor code or any similar monitor that will fit in a 2716 EPROM? I think it was originally written by Graham Dixey who also wrote a whole series on programming the Z80.
Any help appreciated and thanks for your time.

Alf
Alf,

Would that be a Maplin GB86T CPU board fitted with an 8279 Keypad/Display interface chip and connected to a GD40T Hex keypad and display board? If so, I think I can help you out. Drop me a PM.

If you just have the basic GB86T board you'll have to write your own code - I still have the documentation that came with it including details of the edge connector, which was almost, but maddeningly not exactly the same as the Sinclair Spectrum edge connector.

Mine is mounted on a backplate and connected to an IOM-MPF-1P peripheral expansion module originally designed for the 'Micro-Professor' Z80 teaching system, so my monitor eprom has some extra code in it to receive an intel hex upload to the machine via the 8251 UART on the IOM board.

Otherwise, it's the same as the original monitor eprom. I should also have my original (unmodified) eprom around somewhere but, s*ds law, I can't lay my hands on it at the moment.

Drop me a PM.

Graham.
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Old 6th Sep 2011, 6:25 pm   #10
Alf Fisher
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Default Re: Maplin Z80 SBC

Hi Gezza,
Oh yes, those days were fun!
To answer your questions, I think I have all the books you mentioned. I didnt buy my Nascom new but it was from an ex-colleague and about a year old at the time.
Regards,
Alf
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Old 6th Sep 2011, 6:30 pm   #11
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Default Re: Maplin Z80 SBC

Graham,
I've sent you a PM but I am interested in finding out about the Maplin code. I have the 2 articles covering the CPU board and the serial interface with a 8251. If you can locate the code, I would appreciate it.

Best Regards,
Alf
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Old 6th Sep 2011, 7:12 pm   #12
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Default Re: Maplin Z80 SBC

Quote:
Originally Posted by Alf Fisher View Post
Graham,
I've sent you a PM but I am interested in finding out about the Maplin code. I have the 2 articles covering the CPU board and the serial interface with a 8251. If you can locate the code, I would appreciate it.

Best Regards,
Alf
Also responded to you in PM, but for the interest / enlightenment of others the code I have is from the original 'M12' eprom which provided the basic hex-entry monitor utilising the optional on-board 8279 keypad/display IC (U8), plus the additional GD40T hex keypad / 7 segment display board. The GD40T keypad/display board was the original version which used proper key switches for the keypad.

Later on, Maplin produced a (presumably) less expensive version of the display/keypad board which used a membrane keypad instead. I don't know what their part number for that version was.

The weakness of the GB86T/GD40T combination was that it had no other I/O capability on board at all, just 4 decoded chip select lines to start you off with interfacing to your own homebrew I/O via the edge connector.

The 8251 UART board you mention was eventually produced some time later, and I suspect (although I don't know for sure) that it would have been supported by code routines contained within another eprom written to accompany it - either way, the code that I have here was produced before the 8251 add on board existed, and so it does not contain any supporting routines for that board.

Last edited by SiriusHardware; 6th Sep 2011 at 7:19 pm.
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Old 6th Sep 2011, 8:43 pm   #13
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Default Re: Maplin Z80 SBC

Can't seem to re-edit my post above, so here's some additional info I've trawled up from some Maplin catalogues of that era:

In 1992 the price of the CPU board kit LK67X, (built on PCB GB86T), was 33.45 pounds.

By 1992 the 'new' version of the keypad / display kit (Maplin LT15R) with the membrane keypad was the one being offered, built on (Maplin GH21X) PCB. The circuit diagram of the keypad/display evidently had not changed because the eprom to make the keypad and CPU card work together was still the 'M12' type (Maplin UH87U)

After that, the next catalogue I have is March-Aug 99 and by then the add-on serial interface (Maplin LU01B built on GJ25C PCB) had made an appearance. This was marketed as a proper development system and, as predicted, used an updated version of the eprom termed 'MS12' (DT03D). Unfortunately I don't have this eprom.

The combination of Z80CPU board kit LK67X fitted with MS12 eprom and connected to the serial interface board kit (LU01B) was then used with windows PC software (DT04E) to create a complete PC based Z80 development system.
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Old 8th Sep 2011, 6:16 pm   #14
Alf Fisher
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Default Re: Maplin Z80 SBC

Hi Graham,
You are right in saying the EPROM for use with the serial board was MS12 and, in the article I have, it had what I assume is the temporary number of 95037.
As Gezza123 suggested, I will probably end up writing my own but if the M12 only has the limited functionality you quoted, it would be a massive job to disasm it.

Alf
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Old 8th Sep 2011, 9:02 pm   #15
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Default Re: Maplin Z80 SBC

Quote:
Originally Posted by Alf Fisher View Post
Hi Graham,
You are right in saying the EPROM for use with the serial board was MS12 and, in the article I have, it had what I assume is the temporary number of 95037.
As Gezza123 suggested, I will probably end up writing my own but if the M12 only has the limited functionality you quoted, it would be a massive job to disasm it.

Alf
OK Alf, check your email some time.
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Old 26th Oct 2011, 3:57 pm   #16
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Default Re: Maplin Z80 SBC

I built this card by using vero-wire. The keyboard is switches glued together in a balsa case. Still have it upstairs in a box, maybe it is time it is switched on again. My husband things it is a work of art.

Have moved on to the 6502 now as my main processor. I think this is what they call progress.
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Old 28th Oct 2011, 9:03 pm   #17
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Default Re: Maplin Z80 SBC

Quote:
Originally Posted by Cheekyfox View Post
I built this card by using vero-wire. The keyboard is switches glued together in a balsa case. Still have it upstairs in a box, maybe it is time it is switched on again. My husband things it is a work of art.

Have moved on to the 6502 now as my main processor. I think this is what they call progress.
You can't say something like that and not show us a picture. (Of the machine, obviously, not you).
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Old 1st Nov 2011, 5:32 pm   #18
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Default Re: Maplin Z80 SBC

When I get home this weekend I will get it out and photograph the bits...

Andie
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Old 30th Jan 2012, 5:38 pm   #19
Alf Fisher
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Default Re: Maplin Z80 SBC

Hi Andie,
Looking forward to seeing your work of art.
A download of the EPROM contents would also be interesting if you can manage it. Is the EPROM coded M12 or MS12?

Alf
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Old 17th Jan 2013, 11:29 pm   #20
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Default Re: Maplin Z80 SBC

This one? I recreated the source code somewhere as well.
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