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Vintage Computers Any vintage computer systems, calculators, video games etc., but with an emphasis on 1980s and earlier equipment.

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Old 10th Aug 2022, 8:18 pm   #1
ChrisOddy
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Default Tesla Programmer

Last year I started looking at the problem of programming Tesla PROMs and seeing if I could use the existing Acorn PROM Programmer (intended for National Semiconductor PROMs).

Well it turned out not as the programming method is effectively reversed, data lines are pulled low rather than high. It proved difficult to adapt the design to cope with both makes of PROM due to a lack of spare control lines. The easy solution was to build a second programmer card. After a 6 months delay (caused by other project diversions !) I've finally gotten around to finishing it off. I've updated my PROMER2 software to PROMER3 which works with either or both Programmers.

I've put a full description and write up here including the source code: http://www.theoddys.com/acorn/Replic...mer_board.html

Chris
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Old 10th Aug 2022, 8:49 pm   #2
Slothie
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Default Re: Tesla Programmer

Great work! Funnily enough last week I dug out the PCBs I had made and components for my Tesla PROM programmer that was discussed on this forum a couple of years ago and got shelved due to personal issues. I have a translated data sheet for these Tesla PROMs that I made, if anyones interested, but the details are essentially the same as in Chtis's documentation. It's good to see the algorithm I translated from Czech using online tools was correct, as confirmed by Chris's document. I am going to put together the programmer and see if I can get it working. I have a pair of Acorn 1 PCBs I bought off eBay 2 years ago and I think I need to at least start thinking about getting the parts and tools I need to put it together.
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Old 10th Aug 2022, 9:34 pm   #3
SiriusHardware
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Default Re: Tesla Programmer

Thanks Chris, (and Ian, nice to see you around again).

Chris, I note your observation (which has been noted before, I think, by circuitryboy and others) about the similarity between the programming regime for the Tesla devices and the equivalent Texas SN... series devices. That originally gave me some hope that MH74S571s could be programmed by any programmer which supported the SN74S571... but ... Texas seem to have stopped one device lower than that, at the SN74S287. There does not ever seem to have been an SN74S571, so there is no direct Texas equivalent for the 571 which is a pity.

However it does make me wonder if a device programmer which supports the SN74S287 could programme a Tesla MH74S571 in two passes if the MH74S571 was placed in an adaptor which allowed the high address bit to be manually pulled high or low.

I take it the PROMER software runs on an Acorn System 1, which not many people are likely to have. If so, Ian, we still need your alternative based on a more generic, readily available and cheap controller like an Arduino.
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Old 10th Aug 2022, 9:56 pm   #4
joebog1
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Default Re: Tesla Programmer

It is great work!!. A beautifully laid out article. Every part of it is explained!!.
Superb effort.

Joe
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Old 11th Aug 2022, 8:51 pm   #5
SiriusHardware
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Default Re: Tesla Programmer

So Chris, do you plan to sell these PCBs? I know you do sell your MK14 replica PCBs, in fact, one of the regular MK14 contributors here uses one. I didn't see any indication anywhere in your link that these Acorn System 1 Tesla programming PCBs are for sale.
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Old 12th Aug 2022, 8:36 am   #6
ChrisOddy
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Default Re: Tesla Programmer

Yes I do sell the PCB's but you'll need to go to the For Sale page, I don't link from the individual board pages : http://theoddys.com/acorn/For%20Sale/for_sale.html

The PROMER program will not run on a System 1, it needs a VDU, Keyboard etc. so you need at least a System 2 and really a disk based System 3 as I wouldn't want to load it from tape !
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Old 12th Aug 2022, 3:50 pm   #7
TonyDuell
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Default Re: Tesla Programmer

I must look into this, I suspect it would run on one of my System 4 machines (twin disk drives). The one that it won't run on has the 6809 CPU board, you see...
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Old 12th Aug 2022, 4:02 pm   #8
SiriusHardware
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Default Re: Tesla Programmer

I was thinking possibly of removing (or not fitting) everything east of the 8255 and instead controlling the 8255 with a current microcontroller PCB like an Arduino or a Raspberry Pi. (level shifting would be required for the latter, yes, but its in-built mass storage / file system would make the creation, management and selection of programming files so much easier).

The availability of a PCB does make this a more appealing prospect.
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Old 21st Aug 2022, 2:37 am   #9
ortek_service
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Default Re: Tesla Programmer

Yes, Chris, it was good to hear you'd now got this all working OK.

I recall initially 'scoping the Dataman-Pro (Elnec re-badge, and one of very few that supported the Tesla PROM's), to verify its programming method against the somewhat vague info on programming these.
And having to a bit cunning with shunt-diode + pull-up, to have level low-enough to fool it into attempting to program a location, but high-enough to be able to see how long it then held it hard to ground for
- As had initially discovered that it was being 'intelligent', and reading the bits first, to decide whether they needed to be programmed (unlike most EPROM programmers, that just always program, then verify after each pulse).

It was also surprising that Elnec had opted to just have one long 45ms pulse, rather than trying multiple shorter ones, for quicker speed / less heaing, and only one attempt at a location (before completely aborting prog. sequence. - with retrying option going right back to start - although fortunately it then skipped all those locations that had previously programmed OK and read correct)
It seems they'd done something similar for NS-Proms, as I recall previously having one that kept failing at many locations, so had to repeat the sequence many ten's of time, till it eventually-programmed. So maybe their programmability declines with age / that was from a rogue batch.

I never found a common programmer that supported the TI SN74Sxxx 4bit PROM's (Only 8bit ones) - Neither original (Advantech-design) Dataman 48 or the (Elnec-design) Dataman 48-Pro ones (which both do NS ones), to see what they did. So even if you could still get hold of TI PROM's, programming them could be difficult (although it seems Tesla algorithm is so similar, then can use one for that).
It doesn't seem that Tesla just copied TI devices, as there never was a SN74S571, only the '287. Although they did use virtually the same programming recommendations / odd inverted-programming arrangement (With the NS ones seemingly a bit more conventional, even if higher 10V etc. voltages were still needed to be applied).

As NS ones are now getting very hard to obtain, with previous NOS's being exhausted, then Tesla ones seem to be only alternative - especially as 8bit PROM's / parallel (E)EPROM's all tend to be in packages that are too large to make neat adapters for.
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Old 21st Aug 2022, 9:58 am   #10
SiriusHardware
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Default Re: Tesla Programmer

Hi OS, nice to see you are still around. I think one of my two programmers here may support Texas SN-series BPROMS but I will have to look to see if that includes the SN74S287.

I have to say that we all appreciate the investigative work by you and Chris, also circuitryboy who worked on the problem independently - I suppose no matter how careful you are, when you are working with one-shot devices you must have to waste a few while fine-tuning things so there would have been a cost in terms of parts as well as time, Although I suppose you could minimise that a little by only trying to programme individual bits at a time in the early stages of testing, rather than the whole device.
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Old 21st Aug 2022, 3:03 pm   #11
ChrisOddy
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Default Re: Tesla Programmer

I only wasted one Tesla chip ! My test software only programmed one byte or even bit at a time. Once conifdent I then took the plunge and programmed Mk14 and Acorn System 1 chips and they were all fine.
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Old 21st Aug 2022, 5:58 pm   #12
SiriusHardware
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Default Re: Tesla Programmer

That just proves you are the Better Man. I no doubt would have gone through about a dozen before I got it right.

Fear Of Getting It Wrong would have made me keep getting it wrong.

Last edited by SiriusHardware; 21st Aug 2022 at 6:03 pm.
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