4th Feb 2021, 5:37 pm | #461 |
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Re: Non-working Commodore PET 3016
It would be easier if you already had one and knew how to load 'sketches' (programs) into one. If we ask you to get one just for this purpose that will be another long learning arc we will be sending you off on, which you may or may not feel you have time and energy for.
I should probably have asked first if you have any kind of EPROM programmer available to you because if you have, even if the programmer does not directly support those PROMs, you could make an adaptor which would allow them to be read as though they are a more common device. |
4th Feb 2021, 5:53 pm | #462 |
Octode
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Re: Non-working Commodore PET 3016
No Arduino experience and no EPROM programmer here either I'm afraid.
I'm happy to learn if needs be. Might this be an easier route to pursue for a replacement UD7? http://www.vcfed.org/forum/showthrea...ing-MCM-68764C |
4th Feb 2021, 7:19 pm | #463 |
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Re: Non-working Commodore PET 3016
If you want to go that way, yes, but £8 (the price of a programmed MCM68764 from that source) is not insignificant if UD7 turns out not to be duff, and you end up buying another one, and another one, etc.
As the code is 4K and the device is 8K you would have to specify that you wanted the code programmed into the upper half of the IC. I can program those MCM68764s here but you would have to find one and get it to me (which would incur postage both ways) and I think you would be very lucky to find them blank for less than that source is offering them for programmed. The code for all of the PROMS is available online, so what you really want is something which will read the code out of yours and tell you whether the code coming out of them matches the online code. You could maybe use an ordinary Raspberry Pi to to do this because although it outputs 3.3V levels, 3.3V is normally enough to represent a logic '1' to 5V logic inputs such as the address pins on one of those PROMs. You would need some sort of level shifter between the PROM data pins and the Pi inputs used to read the data, otherwise you would risk damage to the GPIO ports on the Pi. (PROM outputs up to 5V, Pi expects only 3.3V max). I seem to remember hearing somewhere that the GPIO pins on the Pi are 5V-tolerant in input mode but I'm not sure that is official and I wouldn't like to try it unless I heard it from Eben Upton himself. If you rigged up something like that up you could check ALL of your PROMs for virtually no cost and then order replacement(s) for the ones you definitely know are duff. Another thing you can do is to make an adaptor which makes a common 2732 EPROM 'look' like one of the original PROMs so you can plug an EPROM in as a substitute PROM, but you would still have to get an appropriately programmed 2732 from somewhere. Last edited by SiriusHardware; 4th Feb 2021 at 7:36 pm. |
4th Feb 2021, 7:33 pm | #464 |
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Re: Non-working Commodore PET 3016
Back in Data Buffer Land, your pairs of pins for scope comparison are:
UE9 2,18 4,16 6,14 8,12 UE10 2,18 4,16 6,14 8,12 We appreciate you can only do this when you have your extra hands available. |
4th Feb 2021, 8:07 pm | #465 | |
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Re: Non-working Commodore PET 3016
Quote:
Colin. |
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4th Feb 2021, 8:07 pm | #466 |
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Re: Non-working Commodore PET 3016
I forgot to say earlier: The most common and best known Arduino is the 'Uno', but that does not have quite enough pins to service the 8 data + 12 address pins + 2 CE pins of one of those PET proms so you'd gave to go up to something like an Arduino Mega 2560.
https://store.arduino.cc/arduino-mega-2560-rev3 Although these, like all of the Arduino series, are great tools to have in your electronics toolbox the Mega is not especially cheap so I would maybe encourage looking at creative use of one of your Raspberry Pis instead, one with a 40-way GPIO header. If you use a Pi you can put the known good binary files of all of the PROMs in a folder and have the reader program (written in Python?) 'verify' the code in the PROM it is reading against the code in the corresponding file. |
4th Feb 2021, 8:12 pm | #467 | |
Octode
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Re: Non-working Commodore PET 3016
Quote:
Colin. |
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4th Feb 2021, 8:12 pm | #468 |
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Re: Non-working Commodore PET 3016
Ref: #465, pins 1 and 19 are the pins used to command the buffer ICs to switch direction - unlike the address buffers which only convey the signal in one direction the data buffers can carry the signal in either direction, either outgoing from the CPU or incoming to the CPU.
So this shows that the CPU is trying to both read and write although I'm not yet sure what to make of the fact that you don't seem to see anything on the other (data bus) pins. |
4th Feb 2021, 8:14 pm | #469 |
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Re: Non-working Commodore PET 3016
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4th Feb 2021, 8:14 pm | #470 | |
Octode
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Re: Non-working Commodore PET 3016
Quote:
Although I accept that if Colin is happier with the Pi that might be an option, although I don't think the Pi's inputs are 5v tolerant. |
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4th Feb 2021, 8:21 pm | #471 | |
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Re: Non-working Commodore PET 3016
Quote:
I do quite like the idea of using a Pi so you can do a direct one for one byte verify against the proper code, that's easiest to do with something which has a filesystem. |
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4th Feb 2021, 8:23 pm | #472 |
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Re: Non-working Commodore PET 3016
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4th Feb 2021, 8:25 pm | #473 | |
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Re: Non-working Commodore PET 3016
Quote:
https://www.ebay.co.uk/itm/Arduino-M...EAAOSwwjVetIEH |
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4th Feb 2021, 8:33 pm | #474 |
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Re: Non-working Commodore PET 3016
That's another example of an Arduino Mega 'clone', yes. Other sellers and clones exist.
I do like those level converters you found as well, so it's up to you. I'm not personally aware of any PROM / EPROM reader software already available for the Pi, but I have not looked for it. I would be surprised if someone has not already done it and anyway, you may feel able to write something like that yourself since you are obviously somewhat familiar with the Pi. |
4th Feb 2021, 8:40 pm | #475 | |
Octode
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Re: Non-working Commodore PET 3016
Quote:
Thanks. Colin. |
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4th Feb 2021, 8:52 pm | #476 | |
Octode
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Re: Non-working Commodore PET 3016
Quote:
If it really is not just very slight noise, then check the resistance of pin 10 to your ground reference point, it should be almost 0. Power off on the board and with red and black both directions. |
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4th Feb 2021, 8:59 pm | #477 | |
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Re: Non-working Commodore PET 3016
Quote:
You might still need an adapter, but easier than connecting level shifters and programming an arduino. It might be better just to send to someone that can verify the proms for you if there are any volunteers. |
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4th Feb 2021, 9:01 pm | #478 | ||
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Re: Non-working Commodore PET 3016
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https://victorengineeringreloaded.wo...re-extraction/ |
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4th Feb 2021, 9:02 pm | #479 |
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Re: Non-working Commodore PET 3016
I'm aware of a publicly available Arduino Mega 'sketch' which is designed to read the code out of a 2716 (2K) EPROM, it would only need a small rewrite to read from a 4K EPROM and you'd just have to wire the PROM to the Mega pins appropriately so that it looked to the Mega as though it was a 2732 EPROM. We can explain all that in more detail if needed, if you get to that point.
The Mega is a microcontroller PCB like the Pi Pico so it doesn't have a filesystem like the 'classic' Pi Linux computer does - instead it would output the code it read over a USB serial connection to the host computer and from there you could save the code and use some other utility to compare the 'good' code with the code read from your PROM. The advantage of going the Pi route is -You already know a bit about the Pi, possibly including programming. -You can put the code files onto the Pi and have your program directly compare the code coming out of the PROM with a known good code file. Disadvantages -Level shifting required, at least on the data bus connections. -You will probably have to write the utility yourself. Edit: That article Slothie found is pretty much what you need if going the Mega route - we can help you with the wiring to the PROM and any small changes needed to the code. |
4th Feb 2021, 9:19 pm | #480 | |
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Re: Non-working Commodore PET 3016
Quote:
Certainly I would do this if Colin didn't mind entrusting them to the tender mercies of the Post Office (both ways). He doesn't seem to mind exploring possible ways to do it himself, though. |
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