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Old 21st Nov 2022, 12:58 am   #1
ortek_service
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Default Newbear 77-68 CPU board - rediscovery

Whilst going through my collection of mainly Nascom boards (after recently joining the Nascom-computers groups.io forum, I found out about at RCF-2022), to see what I had, I rediscovered a (same 8"x8" size, also with a long 78/80pin SIL 0.1" pitch edge connector board - So similar to most Nascom expansion boards) board, marked '7768 CPU'

When I first got this (Free from Drayton Manor Rally, back in 1995 in the days that loads of unsold computer etc. stuff was just left behind by many traders at the end of the day), I didn't know exactly what it was - Well it was a few years before I had access to the Internet / there wasn't originally much info out there on things like this. And it was only after seeing some / finding-out about the Newbear 77-68 system for the first time at the RCF, that I realised exactly what it was and I actually had an original Newbear 77-68 PCB!

The attached picture(s) (others in zip file, to avoid extra-compression) are as I first got it, but it doesn't look like there's too much missing, to complete it - Only a couple of 2112 RAM's (The top has broken-off the only one in the two red-sockets), and a 7404 Hex inverter for the (5MHz) Xtal oscillator. The (optional) 81LS97 (= even less common 74LS797) Data-bus Buffers were never fitted (the DIL20 holes for these are hiding under the grey ribbon cable on mine).

Although the original constructor used very-thin insulated wire for all the top-side links, and some thick insulated wire in parallel in a few places on the underside which doesn't look too neat. And some pins on the edge-connector socket have got broken-off (Not sure how available these 80w - numbered 0? to 79 with pin7 left blank for a key-way - On Nascom but not on this one).

I found there was a helpful Wikipedia page on it: https://en.wikipedia.org/wiki/Newbear_77-68

But I couldn't find the referenced publication: 77 - 68: the Construction of a - Simple Computer - Using a 6800 Microprocessor. Bear Microcomputer Systems (1977)., ASIN: B001P844K8 (Amazon stock number?)

And following the link to the 'A Mighty Micromite' article in the (first issue) PCW magazine, to the Cambridge CfCH computer museum webpage at:
http://www.computinghistory.org.uk/d...8-First-Issue/
there are full-details of the contents (Includes MK14 & Nascom, so the Microbear had been around a bit by then), but the link to this specific article doesn't work. However, the full magazine can be found at: https://worldradiohistory.com/UK/Per...No.1-S-OCR.pdf

The Mighty Micromite article on the 77-68 is 3-pages inc. circuit & parts list (Where they note you may be able to build this CPU+RAM only board for < £50, if you've already got many parts - but you could buy a complete MK14 kit in the same issue for £44!) .
And there's also a 2 page advert / pricelist from the Newbear Computer Store in there - as well as one from Bywood (but no SCRUMPI, only Computer etc. IC's)

I've also attached the relevant Newbear article & Advert extracted pages from this, for ease of access.

I wonder how many on here ever had one of these, that I somehow missed seeing / knowing about all these years (I have one of the older SWTH 6800 systems, I saw at the RCF / have seen feature in various computer books)?
Or even had the extra ROM / RAM cards to be able to run BASIC etc. on it ?
- I've not seen any detailed info on these on the 'net so far (but it appeared a couple of people at the RCF with 77-68 boards may well have still have the original info etc on other parts of this system).

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Old 21st Nov 2022, 10:00 am   #2
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Default Re: Newbear 77-68 CPU board - rediscovery

A lucky (old) find - thanks for taking the time to write up the detailed history and for rounding up all the attached information.

Good job you didn't throw it away before you realised what it was.
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Old 21st Nov 2022, 4:28 pm   #3
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Default Re: Newbear 77-68 CPU board - rediscovery

I followed the 7768 and Tim Moore at the time via the ACC newsletters, the 7768 was fully detailed in there with expansion cards such as ram, vdu, cassette etc, all hand drawn. I'm still very active with 6800 systems, one of many ongoing projects is a SWTPC 6800 repro, and a couple more 6800 projects on Yooch PHILG2864
Dave Williams and his brother (John?) (devilish designs?) were demonstrating the 7768 at the Cambridge do last week, he had it controlling a model railway. Or rather a video of it controlling a model railway Opposite the SWTPC 6800. It can be seen in Kim's video at 13:30 ish https://youtu.be/T0sHJ7tj_OA?t=837
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Old 21st Nov 2022, 5:03 pm   #4
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Default Re: Newbear 77-68 CPU board - rediscovery

First appearance:
http://www.bitsavers.org/pdf/bearMic...sue1_Apr77.pdf
4k RAM:
http://www.bitsavers.org/pdf/bearMic...sue5_Dec77.pdf
More 7768: http://www.bitsavers.org/pdf/bearMic...rSystems/7768/
I have the ACC newsletter with the 7768 VDU circuitry, I'll scan it later.
General 6800 stuff:
http://www.bitsavers.org/components/motorola/6800/

The ETI "System 68" launched about the same time and had a wider audience through the magazine, unfortunately with JMK's passing the System 68 faded away, though it was very capable and all the boards had been published.

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Old 21st Nov 2022, 7:00 pm   #5
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Default Re: Newbear 77-68 CPU board - rediscovery

It was Chris Carter and his brother had the pair of 7768 - I loved the Anthill Inside sticker on the one used to control the Railway layout (If you know TP you will get the reference).

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Ironically Dave (Devilish Designs) can be seen to the top left in the first photo also had one of his 77/68 replicas with him - he has a fully expanded original and a replica of it in a case as well.

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Old 21st Nov 2022, 7:02 pm   #6
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Default Re: Newbear 77-68 CPU board - rediscovery

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Originally Posted by Phil__G View Post
The ETI "System 68" launched about the same time and had a wider audience through the magazine, unfortunately with JMK's passing the System 68 faded away, though it was very capable and all the boards had been published.
And as you will know the first advert for the SCRUMPI was basically the S68 although ETI took it up and changed the CPU to 6800. JMK/BYWOOD did sell an SC/MP card for the system as an alternative.
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Old 22nd Nov 2022, 4:24 am   #7
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Originally Posted by SiriusHardware View Post
A lucky (old) find - thanks for taking the time to write up the detailed history and for rounding up all the attached information.
Good job you didn't throw it away before you realised what it was.
I'd very-rarely throw things like that away! - But may well have been tempted to raid it for any useful parts to fix other systems, although IC's etc. can easily be restored (Someone had removed virtually all the IC's & a few passives etc. from Acorn System cards I'd discovered in 'Rally 50p bargain bags' and it was only a few years later when Chris Oddy was resurrecting his systems that I found out exactly what they were)


Thanks everyone for the links and RCF etc. photos - I do remember them demonstrating these systems to me at the RCF.

I do vaguely recall the ETI System 68, and subsequently have a complete set of back issues, as I probably missed seeing these when they first appeared as a friend only started buying ETI when it had the build your own Space Invaders game feature (Although never got round to doing that). I also recall that some of these microcomputer projects often only gave schematics with no board layouts (not that making fine-pitch tracking D/S PCB's yourself was too easy) or ROM contents published so had to buy these.
Although an SC/MP card would surely be a bit of a downgrade even from a 6800, so I can see why the 6800 was preferred on ETI.
(And I recall that one of the founders of Acorn had wanted to use a nicer processor than the SC/MP whilst at Sinclair so had left and basically made a 6502 version of the MK14 - although a bit more modular to allow later expan of this 'System' range).

I hadn't discovered that so much info had been preserved at: http://www.bitsavers.org/pdf/bearMic...rSystems/7768/
And I notice that the collection of photos there - With 'Triton-1' (I thought that was ETI 8080 system) named wooden cased system. Plus I see they've got the same quite-large 1/2W? resistors, mine has. But all of these have the ribbon cables a bit better than mine, not going over buffers IC's etc. space.
It would be nice if the 77-68 Wikipedia page pointed to some of that.

The '77-68 Construction of a 6800 Microcomputer' one looks very-familiar, and I think I've got an original printed copy of this - I might have got it from my old Uni Microcomputer Club when I got the 6800-based SWTPC system I need to get going sometime:
https://deramp.com/swtpc.html
(I will probably readout all the >45 yr old EPROM's, to see what's in these / if still OK. Although I suspect back then they were all 3-rail 2708's etc so will have to make an adaptor for more modern single-rail only IC-programmers). I have also recently re-found some '(c)1979 Smoke Signal Broadcasting SCB-68' 6800 CPU / ROM / 1K RAM cards (So more on one card than SWTPC ones?) I'd also bought very cheap (20p each!) >20yrs ago that seem to be compatible with the SWTPC system's SS-50 backplane. See here for a bit of info on these: https://en.wikipedia.org/wiki/Smoke_Signal_Broadcasting
https://deramp.com/downloads/swtpc/h...0Broadcasting/

Re: http://www.bitsavers.org/components/motorola/6800/
I think I have the original printed copies of many of these. And did quite a bit of assembler on a 6802 back in 1990 - before moving onto 68HC11's (that became very popular a few years later, Inc. using IAR C-compilers on those).

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Old 22nd Nov 2022, 11:36 am   #8
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Default Re: Newbear 77-68 CPU board - rediscovery

>>I suspect back then they were all 3-rail 2708's
I had a few 2708s to dump so made a dedicated little reader, its something you use once so dont bother making anything Owen just borrow this one. Its dead easy to use, the reader talks to a PC via USB (CH340G) and sends an Intel hex file at 9600 which you can capture in Teraterm or whatever. Its only a crappy little veroboard thing but does the job perfectly.
Let me know and I can post it with the ULA.
BTW I have loads of SWTPC s/w.
Cheers
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Old 22nd Nov 2022, 2:12 pm   #9
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Default Re: Newbear 77-68 CPU board - rediscovery

Fascinating! I remember back in the very-early-80s going to Newbury Labs (in.... Newbury of course) to get some new character-generator PROMs for the dot-matrix printers they were selling at the time, and they had all sorts of odd bits of microcomputer stuff.

Never came across the Newbear but I know someone who had a NewBrain, which was a BBC-Micro-sized device which ran CP/M 2.2
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Old 23rd Nov 2022, 1:24 am   #10
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Default Re: Newbear 77-68 CPU board - rediscovery

The Newbrain was actually quite a bit smaller than the Beeb - more Acorn Electron / small Laptop ./ Notebook size.
I think I might have one (or at least some parts of) somewhere.
And never seemed to be very common, mostly only seen in old computer magazines.

Although I hadn't realised it was apparently that it was to be the original BBC-badged microcomputer, but the manufacturer didn't tender for this, according to: https://en.wikipedia.org/wiki/Grundy_NewBrain
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Old 23rd Nov 2022, 9:32 am   #11
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Default Re: Newbear 77-68 CPU board - rediscovery

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>>I suspect back then they were all 3-rail 2708's
I had a few 2708s to dump so made a dedicated little reader, its something you use once so dont bother making anything Owen just borrow this one. Its dead easy to use, the reader talks to a PC via USB (CH340G) and sends an Intel hex file at 9600 which you can capture in Teraterm or whatever. Its only a crappy little veroboard thing but does the job perfectly.
Let me know and I can post it with the ULA.
BTW I have loads of SWTPC s/w.
Cheers
Phil
Thanks for the offer of the loan of this, but I think I'll knock-up a simple adapter for reading these as a (twice repeated 1KB image) standard 2KB single-rail 2716 anyway, as I've a few 2708's on some other boards I'd also like to readout and this allows it to be used with standard programmers I have, until I finish the Softy-1 replica that will also be able to program 2708's (Although getting readouts off it is a bit involved, with it being easiest to temporarily program read-contents back to a single-rail 2716 for readout on more-recent PC-programmers that don't usually support multi-rail types - There was an adaptor for later Dataman Pro programmers, with on-board extra supplies, but fairly expensive at > £100)

I have previously made various MM55132 etc ROM to a standard EPROM adaptor, for verifying those, by just stacking a few IC sockets and some minor pin re-mapping / gating / inversion of CS inputs, as required.
And I managed to design & make a rather more involved MM5204 2-rail 512Byte totally non-JEDEC standard pinout EPROM (as used on the NS Introkit) to 2716 readout adaptor in 2-3hours - Even though I only needed to use it once (Although Chris also borrowed it and worked for him on his programmer as well), so just fed fed the (extra) supplies from external PSU's, schottky-diode combining the device's +5V Vcc supply with one from programmer and an external PSU so that both MM5204 supplies could be switched on together without upsetting the programmer / avoiding the need for a relay etc fed from Vcc pin to switch extra (-)12V supply.


However, it would still be interesting to see what your 2708 reader consisting of (Presumably a microcontroller on the veroboard, that has port lines to EPROM's I/O and with UART interface to a PC).
So if you have any photos / schematics / firmware files you can share, I'm sure it would be of interest to many of us / those without an EPROM programmer at all.

- Presumably it does require a few external PSU's, unless you managed to integrate a couple of extra DC-DC's for the +12V / -5V rails like these ones that also program the 2708 etc:

A shield for the Arduino Mega 2560 R3: https://www.mattmillman.com/projects...m68766-eproms/

And Martin Eberhard's 'Orphan EPROM' etc. Programmer: https://deramp.com/downloads/mfe_arc...20Programmers/

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Old 23rd Nov 2022, 10:53 am   #12
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Default Re: Newbear 77-68 CPU board - rediscovery

The Newbear was the first computer I built. Very expensive 6800 chip and RAM. Built up on veroboard with a cardboard front panel using rocker switches for address and data. Very annoyed when SWBO unplugged my power after typing in a (relatively) long program.
Scanned the Newbear booklet into an unreasonable 250MB pdf, Compressed that online to 6MB but it made the circuit unreadable. Replaced the compressed circuit with the original - but the final pdf is still 12MB so it is available from https://mega.nz/file/clhEXZCL#6RWhh1...f-JL03ULj89hyE which site seems safe - but could also email if preferred (PM).
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Old 23rd Nov 2022, 6:40 pm   #13
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Originally Posted by ortek_service View Post
However, it would still be interesting to see what your 2708 reader consisting of (Presumably a microcontroller on the veroboard, that has port lines to EPROM's I/O and with UART interface to a PC)
It really was just a very quick one-off just to dump my old Nascom 2708s, hence I didnt go to the trouble of documenting it or doing a PCB.
I'd not seen those examples Owen, obviously if you have to make something to read old eproms then it might as well program them too.
I realised of course that my reader would be obsolete after doing its job, but that 'on loan' it might save others the trouble
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Old 23rd Nov 2022, 11:41 pm   #14
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The Newbear was the first computer I built. Very expensive 6800 chip and RAM. Built up on veroboard with a cardboard front panel using rocker switches for address and data. Very annoyed when SWBO unplugged my power after typing in a (relatively) long program.
Scanned the Newbear booklet into an unreasonable 250MB pdf, Compressed that online to 6MB but it made the circuit unreadable. Replaced the compressed circuit with the original - but the final pdf is still 12MB so it is available from https://mega.nz/file/clhEXZCL#6RWhh1...f-JL03ULj89hyE which site seems safe - but could also email if preferred (PM).
Thanks for that. I've just managed to download it (that mega.nz site was rather fussy about needing a 'modern' browser, so had to switch PC and work system barred access to it earlier).
However, this construction manual (which I'm sure I've actually got a printed original somewhere) was already available (albeit 21MB file) at: http://www.bitsavers.org/pdf/bearMic...nstruction.pdf

- along with some other documentation on this , at link Phil_G gave earlier in this thread: http://www.bitsavers.org/pdf/bearMic...rSystems/7768/
(In Documentation directory)
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Old 24th Nov 2022, 12:18 am   #15
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Default Re: Newbear 77-68 CPU board - rediscovery

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Quote:
Originally Posted by ortek_service View Post
However, it would still be interesting to see what your 2708 reader consisting of (Presumably a microcontroller on the veroboard, that has port lines to EPROM's I/O and with UART interface to a PC)
It really was just a very quick one-off just to dump my old Nascom 2708s, hence I didnt go to the trouble of documenting it or doing a PCB.
I'd not seen those examples Owen, obviously if you have to make something to read old eproms then it might as well program them too.
I realised of course that my reader would be obsolete after doing its job, but that 'on loan' it might save others the trouble
Thanks for the info on this. I do have some 'Mini pro' (aka nano) Arduino modules, I bought from the Far-East (as were cheaper than the just uC IC!)
And the .ino opened OK in my old Arduino IDE, so could program one up / hack the C-code for use in reading-out other IC's with a bit of h/w connections altering).
Whilst I do have some spare 2708's / can still buy them for not too much, I think I'd be tempted to just swap to a single-rail 2716 etc. and isolate the extra power rail pins / reconfigure any pin differences using a simple stacked sockets adaptor - Unless it was very desirable to keep something looking original and wanting to permanently replace a missing / faulty 2708 etc.
- Although swapping the 2-rail non JEDEC std pinout MM5204 in NS Introkits to a 2716, is rather more work. And there is also a dedicated programmer to build for MM5204's eg: https://deramp.com/downloads/mfe_arc...ammers/ME5204/

That 'Orphan EPROM' Programmer also features in a comparison video:
https://www.youtube.com/watch?v=Gdmsni8cGvY

Co-incidentally, I'd also like to readout some IC's on my Nascom(2), although IIRC they are all Mask-ROM's (Not sure yet if all single-rail by the Nascom-2), plus a few Bipolar-PROM's.
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Old 24th Nov 2022, 12:35 am   #16
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I didnt realise you were a fellow Nascom fan Owen... are you a member of the group?
https://groups.io/g/Nascom-Computers/topics
Both of my own Nascoms from back in the day were skipped (sob...) but I now have one of Neil's Nascom-4 boards which is superb.
T2, T4, BBug, nas-sys 1,2,3, Zeap, Pascal, Polydos, etc - all available via a menu!

Re the eproms, I almost exclusively use 2k, 8k and 32k x8 EEPROMs. So much easier and quicker turnaround.
I do have a very posh RS eraser and a boxful of eproms but they're such a faff!
Even my SC/MP has Kitbug+ in one of Sirius's CAT28C16's ! (Ta, G!)

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Old 24th Nov 2022, 12:44 am   #17
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Quote:
I'd also like to readout some IC's on my Nascom(2), although IIRC they are all Mask-ROM's (Not sure yet if all single-rail by the Nascom-2), plus a few Bipolar-PROM's.
I got involved in a Nascom 2 repair, remotely as usual, where one of the bipolar PROMs and the 24-pin PROM containing NAS-BAS had both failed. The Bipolars are 74S188 (or equivalent 82S23) and 74S287 (Or equivalent 82S129) and the BASIC ROM I think we replaced with an MCM68764 (or maybe MCM68766). I have some known good blank 82S129s should you find you need one.

There are Arduino sketches for reading out the contents of PROMs lying around in various threads in this subsection, but it sounds like you already have something along those lines.

At the time I was involved in this I found that the hex code for all of the Nascom 2's bipolar PROMs was well documented online but presumably you want to read those devices to verify that they are OK, or just to back up the code.
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Old 24th Nov 2022, 12:55 am   #18
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I didnt realise you were a fellow Nascom fan Owen... are you a member of the group?
https://groups.io/g/Nascom-Computers/topics
Both of my own Nascoms from back in the day were skipped (sob...) but I now have one of Neil's Nascom-4 boards.
Yes, I've recently joined that group after discovering about it at the RCF from speaking to Neal Crook / the SWTPC exhibitor who said to talk to Neal about Nascoms.
So it prompted my to have a rummage through an old Nascom 19" rack box I bought 30yrs ago, that I'd filled-up with various Nascom (and quite a few other boards I'd later acquired like Newbear, Infotron, Trend SK 947 (Z80), SSB SBC-68 & other 6800 boards) when I'd moved house nearly 20yrs ago and had sat in the garage since then, until recently.

And I'm now going through these, to work out what they all are & see what can be got running / what firmware etc, can be readout to preserve copies of.
Although I mostly have two Nascom systems, after being given a couple of boards & PSU of a Nascom-2, it seems like I may unfortunately only have one CPU board, so may have to look into re-creating another. But I do at least have two Nascom (uncased) keyboards (Nascom-2, and more recently picked-up one for a Nascom-1)

Quote:
Originally Posted by SiriusHardware View Post
I got involved in a Nascom 2 repair, remotely as usual, where one of the bipolar PROMs and the 24-pin PROM containing NAS-BAS had both failed. The Bipolars are 74S188 (or equivalent 82S23) and 74S287 (Or equivalent 82S129) and the BASIC ROM I think we replaced with an MCM68764 (or maybe MCM68766). I have some known good blank 82S129s should you find you need one.

There are Arduino sketches for reading out the contents of PROMs lying around in various threads in this subsection, but it sounds like you already have something along those lines.

At the time I was involved in this I found that the hex code for all of the Nascom 2's bipolar PROMs was well documented online but presumably you want to read those devices to verify that they are OK, or just to back up the code.
Co-incidentally, someone was recently asking about a PROM IC (address decoder for adding UART to I/O board) on the Nascom group.io forum. The manual just called-up a 7603 / 5603 PROM, programmed with SPD/1-L(-H), but I hadn't seen contents of this particular 32 x 8bit PROM there. Neal has replied that it can be substituted with a couple of logic IC's circuit, but it should be possible to work out a look-up table from that and program a suitable PROM (74S288 and 82S123N appear to be equivalents that are more readily-available / more-commonly supported by common IC-Programmers)

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