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Old 14th May 2024, 11:31 pm   #21
Mark1960
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Default Re: Acorn System 1

Where an 8154 is used for a fixed purpose on the Acorn for the keyboard interface it might be possible to replace with standard TTL. This would depend on having a good understanding of the Acorn monitor and the features of the 8154 that are used.
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Old 15th May 2024, 2:49 am   #22
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Default Re: Acorn System 1

Yes, the INS8154 (if you ignore the little-used on the Acorn System at least 128Byte SRAM) is a fairly-basic PIA with two 8bit I/O ports that each have their own Data Direction Register and a Read/Write Data registers.

So you could build one out of a variety of logic IC's, but it might end-up being quite large so may be better using some GAL's etc. (CPLD's / FPGA's will now all be 3.3V max I/O, so would need extra bidirectional-capable voltage-translators.

However, as some other PIA's (/ VIA's, like the 6522) have the same registers and address arrangement, then it is much-easier to just use those with a bit of pin-remapping.

And I see that was what was done on this updated Acorn System-1 design: https://hobbyelectronics.net/2023/01...tem-1-replica/


There was also a discussion on here a few years ago, about recreating a INS8154 (Probably more for a MK14, where it seems it was mainly usually only used to give a bit more RAM): https://www.vintage-radio.net/forum/....php?p=1331685

Also some discussions on Stardot - the main dedicated site for anything Acorn related: https://stardot.org.uk/forums/viewtopic.php?t=16619


BTW, It seems Acorn later iff-loaded all the System support to Control Universal, who had been a distributor of these / had made their own System-compatible Eurocards with alternative processors. With this website having webpages showing their products from their catalogue: http://www.vintagecomputer.net/fjkra...section_03.htm
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Old 15th May 2024, 5:51 am   #23
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Default Re: Acorn System 1

Quote:
Originally Posted by ortek_service View Post
Yes, the INS8154 (if you ignore the little-used on the Acorn System at least 128Byte SRAM) is a fairly-basic PIA with two 8bit I/O ports that each have their own Data Direction Register and a Read/Write Data registers.
For the keyboard interface the data direction control is probably not used, so that could allow some simplification.

If the bit addressable output or input function is used this could possibly be implemented with 74ls259 or 74ls251. It only really gets complicated if both byte and bit addressable functions need to be supported.

The bit addressable functions are probably not such a big advantage with the 6502, but are very usefull with the 8060.
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Old 15th May 2024, 8:21 am   #24
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Quote:
(Probably more for a MK14, where it seems it was mainly usually only used to give a bit more RAM)
I respectfully disagree, the (optional) 8154 on the MK14 greatly increases the machine's 'play value' by adding the 16 extra lines of I/O. I used it a lot back in the day, as it made the MK14 into what might be considered a 1970s forerunner of the Arduino. The extra 128 bytes of RAM was also pretty vital on a machine which was so short of RAM that the VDU, if fitted, consumed all of the standard and optional extra 2111 RAM.

I would have thought the second 8154 on the System 1 was also fairly essential because, unlike the SC/MP which at least has a bare handful of hardware inputs and outputs on-chip, the 6502 does not - so as far as I can see, output on the basic System 1 without the second 8154 is limited only to the display. (Of course you can connect any number of interesting and less rare peripheral ICs via the expansion bus on the edge).
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Old 15th May 2024, 12:04 pm   #25
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Default Re: Acorn System 1

Well I was thinking about released programs for it - like the many games recently put on here.

If you did want to do some hardware interfacing, and writing your own software, then you could always add your own alternatively more-available PIA (or just some addressable latches / input buffers) to the SC/MP Bus.


On the Acorn System, you can also still add any PIO etc onto the System expansion Bus, so don't really need to have the 2nd 8154 to provide the I/O on-board (Although it does make the System 1 a bit more self-contained that way).
You could also add a different PIO with a pin-adaptor onto the original 6502 CPU board that had a socket for that. add register compatibility may not be so much of an issue, if writing your own software t interface to that (There probably wasn't much released that did use this and you'd probably really want a System 2 at least to be doing more involved programming & control).

The use of the 8154 by Acorn was quite short-lived, as on their System 'v.i.b. (Versatile) Universal Interface' expansion card they used both the 6522 and the 8255.
But as the'd committed to the 8154 for both System 1 Keypad/Display and S2/3/4 full Keyboard on the 6502 CPU card and system you make unfortunately requires at least one of these - or an equivalent circuit, which is why many have used the (more-fitting for the 6502 family) 6522 (as used in the Beeb), with suitable pin-out adapting.

So the 8154 probably really suits using with the SC/MP better - to keep everything in the same manufacturer's family.

Last edited by ortek_service; 15th May 2024 at 12:21 pm.
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Old 15th May 2024, 12:47 pm   #26
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Default Re: Acorn System 1

I'm not sure, but I think some of the games released by realtime / CS2 have the option to use 8154 I/O port pins to trigger a custom sound module, so in that sense at least there is recent / current software which does use the 8154 I/O ports.

The only demonstrated use of the 8154 in the MK14 manual was to drive an 8-bit parallel DAC for the 'Function Generator' program but I used it for all sorts of other custom purposes, for example to generate CB PLL codes to make it easier to compile and test the contents of channel code converter EPROMs - at the time the only way I could get an EPROM programmed was to send it off somewhere with a hand written hex listing so I had to be sure that every code in the table was correct beforehand.

I expect that the 2nd 8154 on the System 1 found similar uses by other hardware tinkerers.
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Old 15th May 2024, 1:26 pm   #27
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Default Re: Acorn System 1

I should have said that the (optional) DM74S571 PROM programmer for the MK14 also required the presence of the INS8154. The Nat Semi (DM prefix) version of the PROM is virtually unobtainable now so that isn't going to find much use these days. I don't think I have ever come across anyone who did have the MK14 PROM programmer.
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Old 15th May 2024, 6:43 pm   #28
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Default Re: Acorn System 1

I think coolsnaz2 said he had one.

https://www.vintage-radio.net/forum/...8&postcount=47
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Old 15th May 2024, 7:39 pm   #29
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Default Re: Acorn System 1

Good spot!

As far as I know the Acorn system 'x' also eventually acquired a DM74S571 programmer card which Chris Oddy made a replica of, and then also made an 'alternative' replica specifically to programme the more available but awkward to program Tesla MH74S571. I don't know what minimum level of Acorn system (1? 2? 3? 4? etc) you'd need to support either of those PROM programmer cards.
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Old 15th May 2024, 9:43 pm   #30
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Default Re: Acorn System 1

I've just tried the emulator linked to in #14 on this Win10 64-bit machine - the download is just an acornEmulator.exe file and a license.txt file. When run, it creates a additional .ini file. These files all checked out for me with Windows Defender but as always, you should take your own precautions when downloading and running executable code.

It appears to work well, in so far as I can navigate to different addresses within the RAM range and go back and forth entering code. I haven't tried to run anything yet but it looks promising. The GUI looks nice and the emulator lets you use the equivalent PC keyboard keys for entry as well as by clicking on the buttons on the authentic looking on-screen keypad.
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Old 15th May 2024, 10:22 pm   #31
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Default Re: Acorn System 1

Quote:
Originally Posted by SiriusHardware View Post
I've just tried the emulator linked to in #14 on this Win10 64-bit machine - the download is just an acornEmulator.exe file and a license.txt file. When run, it creates a additional .ini file. These files all checked out for me with Windows Defender but as always, you should take your own precautions when downloading and running executable code.

It appears to work well, in so far as I can navigate to different addresses within the RAM range and go back and forth entering code. I haven't tried to run anything yet but it looks promising. The GUI looks nice and the emulator lets you use the equivalent PC keyboard keys for entry as well as by clicking on the buttons on the authentic looking on-screen keypad.
Just for a laugh quickly tried it on my Ubuntu 22.04 and it runs fine just clicking on the EXE. Not done much but, will have a play - nice find.
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Old 16th May 2024, 12:48 am   #32
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Default Re: Acorn System 1

Um.. since when does Linux run Windows executables? Do you have WINE installed, or something like that?
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Old 16th May 2024, 1:59 am   #33
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Default Re: Acorn System 1

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Originally Posted by SiriusHardware View Post
>>
As far as I know the Acorn system 'x' also eventually acquired a DM74S571 programmer card which Chris Oddy made a replica of, and then also made an 'alternative' replica specifically to programme the more available but awkward to program Tesla MH74S571.
I don't know what minimum level of Acorn system (1? 2? 3? 4? etc) you'd need to support either of those PROM programmer cards.

Well hardware-wise the Acorn System PROM-Programmer should work with any System 1/2/3/4 as these all have the same 6502 CPU card.
And the Acorn PROM-Programmer has its own on-board 8255 PIO, directly on the CPU's address / data bus, not using the 6502 CPU Card's 2nd 8154 PIA, as the two I/O ports on that only go to the DIN41612 'B' row connections - which were never originally connected between the DIN 41612 connectors on the Acorn's original backplane PCB's.
This webpage Chris has done illustrates very-well what the 'B'-row on each of the Acorn System Cards was used for: http://www.theoddys.com/acorn/the_ac...backplane.html
- It's interesting to see that there are NRDS & NWDS signals on this (which originated with the SC/MP), rather than just the 6502's R/~W and Chris mentions elsewhere that there was apparently originally a 'System-75' (but no photos of one?) using the SC/MP, before Acorn switched to the 6502 CPU.


Chris's version of the Backplanes do also connected the B-rows, to avoid the original intention of having to hard-wire the 'B' row between certain connectors that meant some cards could only be used in one dedicated slot for it.
However, that does mean you have to be careful to disable any conflicting 'B'-row connections on some cards. And so Chris says he doesn't actually ever fit the 2nd 8154. So that's probably why he dropped it on the System 1 Trainer single-board version (and probably also to save space and cost) - as was also done on this version: https://hobbyelectronics.net/2023/01...tem-1-replica/

On the original Acorn PROM-Programmer you did have to put +26V (EPROM's) / +12V (Bipolar PROM's) on certain 'B'-row pins.
But Chris didn't like having the +12V on the backplane, as the pin is right next to a +5V supply pin (although at least these connectors shouldn't be able to short adjacent pins together when inserting compared to Card-edge connectors with Sinclair notoriously putting +9V & +5V next to each other on the ZX Computers!) - although there's the possibility of a solder-short on a just-assembled board, if not careful.
So he made provision to provide these extra supplies directly to the card, without going via the System bus, on his replica versions.

However, the original 'System-1' wasn't really physically designed to be used with expansion-cards, that have the same Plug-type of DIN41612 connector, so a backplane of sockets is need. And you'd then need some improvisation to physically-support a vertical-running backplane PCB and cards above the horizontally-flat System-1 boards with the same issue with Chris's System 1 trainer version. But you could always remove the original System 1's top PCB / cut-off the front part of Chris's System 1 trainer, fit the 6502 CPU part into a small-rack and then reconnect the Keypad-Display board part with a long-enough ribbon-cable to the 6502 CPU in the rack.

The other more major issue is the original PROM-Programmer software needs text-commands typing so needs a proper ASCII-Encoded QWERTY-keyboard?) + VDU. And the > 1KB software would have been on Cassette (For System 2) / Disk (For System 3/4) so 4KB 'DOS' (+BASIC) or 2KB 'COS' firmware may be required.
Whereas I think the System-1 only originally had 512Bytes 'Monitor' firmware in the PROM's (which did support cassette loading / saving) but to use the original PROM-Programming software you needed to 'upgrade' to 'COS' (which presumably then needs a full ASCII-encoded QWERTY Keyboard + VDU card as it doesn't support the Keypad/LED-Display)
The System 1's 1KB RAM (2KB on Chris's Trainer version) is maybe enough to load a simpler PROM programmer routine & buffer the data to go into the PROM (assuming COS etc will let you load / save a PROM binary image file).
- But not enough for the larger (E/OTP)-PROM's, the hardware supports.

This webpage has quite a bit of info / links for the original Acorn PROM Programmer: http://www.theoddys.com/acorn/acorn_...mer_board.html

Last edited by ortek_service; 16th May 2024 at 2:09 am.
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Old 16th May 2024, 10:42 am   #34
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Default Re: Acorn System 1

Quote:
Originally Posted by SiriusHardware View Post
I've just had a look through the user manual here, for the first time:-

https://hobbyelectronics.net/wp-cont...UserManual.pdf

I have to say that if this was my first encounter with any programmable 'thing' that manual would have looked quite daunting - the MK14 manual is often criticised for being quite a poor guide for the absolute beginner, and so it is, but the System 1 manual is slightly worse IMO.
>>
>>
Well I suppose virtually everyone buying these back then would have been a beginner, as it would have most-likely been their first "computer".

But it was maybe mostly Electronics enthusiasts who bought these who were prepared to do quite a bit of experimentation and self-learning, rather than expecting much of a training course in the fairly-short 80page Acorn System User Manual - that unlike the SoC 11page manual, had the construction & hardware details in a separate 31page Technical Manual:

http://www.theoddys.com/acorn/acorn_...l%20Manual.pdf

I think there was only one version of the Acorn System 1 User manual, unlike the MK14 having an updated manual. But there was an extra 4 page errata sheet: http://www.theoddys.com/acorn/acorn_...1%20Errata.pdf
And there is an alternative scan of the User Manual split into 80 individual pages, here: http://www.theoddys.com/acorn/acorn_...s%20Manual.pdf

However, Acorn oddly wrote the entire manual in Capital letters! (Maybe they did use an early computer + printer that didn't have lower-case, but I would have thought Typewriters would still have had to be used back then / Manual typesetting would have been required - especially to include the diagrams - as most Computers weren't really capable of doing much in the way of word-processing back then). And this might have resulted in less total content.

Acorn did choose to dive straight into trying to teach you about computing numbering systems, whereas SoC approach was a bit more gradual, having that part much further-on and starting (after the construction) with the operation of the MK14.

Trying to teach you assembly-language programming from scratch in only a few pages dedicated to that is quite an ask.
So things for beginners were rather easier later on, with both the Sinclair ZX-series and the BBC computer coming with much more extensive ring-bound manuals and guiding you more gentle into much-easier to learn BASIC programming.
Compared with it being said that many MK14's were re-sold shortly after buying them, by people who hadn't got on too well with using these, so not sure what happened with Acorn System 1's (maybe much less were sold?)

Although much later on, both only gave you a 'Welcome guide' manual, and you had to buy more-extensive manuals.

However, I'm not sure if some of the early ones like the Acorn System actually came with the User Manual or whether you had to pay a bit extra to buy it separately.



Quote:
Originally Posted by SiriusHardware View Post
>>
>>
The use of not just one, but two nearly unobtainable INS8154 I/O RAM ICs and two equally exotic PROMs must make these replicas pretty expensive to put together nowadays.
Well at least Acorn used still fairly cheaply available more-common 2114 RAM's, rather than the 2111's on the MK14 that can cost you more for a set of 4 than the SC/MP or an 8154. And you always got 1KB as standard, so 4x that of the minimal MK14 / twice that of the MK!4 with all four 2111's fitted.
And the 6502 CPU is also much cheaper to obtain than the (always comparatively-expensive) SC/MP-II

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Old 16th May 2024, 6:14 pm   #35
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Um.. since when does Linux run Windows executables? Do you have WINE installed, or something like that?
Yes its been a very good standard install on many distros for quite some time - very capable now to run most older software and a lot of modern executables, .net in the form of mono is also there!

For example I run the Windows executable for my Xgpro v7.30 programmer as it is very convenient and works well.
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Old 16th May 2024, 8:57 pm   #36
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Default Re: Acorn System 1

Hi All

Just catching up with the forum having been in the US for the last 3 weeks !

As Owen says I have a replica System 1 CPU board but haven't made a keyboard PCB though I recently had somebody ask if I could make one ? I could do a version with the tactile switches used on the 'Trainer' but I think this chap wanted something that looked more original ?

My 8154 stocks are now pretty low hence no more 'Trainer' kits (I think I have sold 30+ ?). The System 5 CPU (a 2MHz 6502) uses a 6522 in place of the 8154 and this is software compatible with the system 2/3 COS and DOS OS's i.e. with an ASCII keyboard. I'm not sure the same would apply with a System 1 display and hex keypad ? might need some mods to the System 1 'Monitor' code ?

Chris

PS I hope to soon have a stock of the AY-3-4592 keyboard chips that are used on the System 2/3/4 ASCII keyboard (and they'll be considerably cheaper than Little Diode !)
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Old 17th May 2024, 12:22 am   #37
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Default Re: Acorn System 1

Hi Chris, welcome back - I wonder if those keyboard chips are something you've sent back to yourself on a slow boat - I've never been to the USA but there are any number of parts that I would probably try to order while staying with relatives that I could get them sent to.

I've had a go at programming on the the emulator - the aim was just to display and maintain the word 'Acorn' on the display and I did manage that but the JMP FF04 exit used in all the manual programs seems to write garbage, possibly a representation of the content of the accumulator or something like that, to the rightmost display cells. (Attached, a screen grab from the running emulator).

Still, I'm not too unhappy with it as I have never written anything for this system before and I last wrote 6502 code in the early eighties. I'm not sure if this will work on a real machine because I would normally expect to have to go into a continuous loop to maintain the multiplexed display - I suspect the emulated display holds and continues to display the last thing written to it in the way that the real thing wouldn't.

I'm too old and too lazy to try to code directly in Hex nowadays so I used SBASM3 to write it and then just typed it in manually. One good feature of the emulator is a binary file save / binary file load function, so you can quickly save any dubious code before trying to run it just in case it runs wild and dismantles itself.
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Old 17th May 2024, 12:38 am   #38
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Hi Chris,

Welcome back! - I hope you managed to get some bargains out there (even if not any vintage IC's).

I imagine you'd really want to use something like the Cherry switches you'd looked at / found a reasonably-priced source for on a proper Qwerty keyboard, where you might want to do quite a bit of typing.

I think the 6522 should probably work OK software-wise on the System-1, as they had used it on this updated version of it: https://hobbyelectronics.net/2023/01...tem-1-replica/

But not sure if max output currents are high-enough, being as Acorn directly drive the display from the 8154's ports (keyboard interface / keypad matrix lines) lines and don't use the 7408's that the MK14 had (Although even those don't really source that much, compared to their sink current). However, the modern 7-segment displays we've been using on the Trevor Hamlett adaptor boards are quite high efficiency and don't need much drive current for a good brightness.

Good news on the AY-3-4592,s, although IIRC it does need an extra (12V?) supply voltage compared to some other single-rail versions. But it does make it easier to keep it a bit more original / not having to use a different matrix arrangement (although that may not matter too much, if having to make the entire keyboard assembly from individual switches and not using a ready-matrixed one).
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Old 17th May 2024, 10:55 am   #39
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Welcome back Chris, and thanks for providing the PCBs etc and the initial help you gave me via your ebay shop. I really enjoyed putting the replica together and my initial messing about with it.

I will further update this thread as I have a chance to play with the unit more.
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Old 18th May 2024, 2:43 pm   #40
Alan Bain
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Default Re: Acorn System 1

Here are a few pictures of my original System I for entertainment value. After many years in storage the CPU socket became unreliable (eventually found using an anachronistic HP16500 logic analyser -- which has in common with the system I the fact that it doesn't have nearly enough keys on the keyboard, it dates from the HP one knob era) and I replaced the socket with a turned pin one. I remember working through the exercises in the all upper case user manual.

Alan
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