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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 4th Feb 2021, 4:37 pm   #461
SiriusHardware
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Default 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.
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Old 4th Feb 2021, 4:53 pm   #462
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Default 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
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Old 4th Feb 2021, 6:19 pm   #463
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Default 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 6:36 pm.
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Old 4th Feb 2021, 6:33 pm   #464
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Default 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.
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Old 4th Feb 2021, 7:07 pm   #465
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Default Re: Non-working Commodore PET 3016

Quote:
Originally Posted by SiriusHardware View Post
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.
I didn't need to trouble the third hand - the only pins I get a discernible square wave from are pins 1 and 19 of both UE9 and UE10. All others give no reading (with the exception of pin 10 which gives a strange non-square reading on both ICs).

Colin.
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Old 4th Feb 2021, 7:07 pm   #466
SiriusHardware
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Default 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.
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Old 4th Feb 2021, 7:12 pm   #467
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Default Re: Non-working Commodore PET 3016

Quote:
Originally Posted by SiriusHardware View Post
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.
Ever one for a challenge - do these look suitable?

Colin.
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Old 4th Feb 2021, 7:12 pm   #468
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Default 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.
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Old 4th Feb 2021, 7:14 pm   #469
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Default Re: Non-working Commodore PET 3016

Quote:
Originally Posted by ScottishColin View Post

Ever one for a challenge - do these look suitable?

Colin.
I think you may have mislaid a link.
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Old 4th Feb 2021, 7:14 pm   #470
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Default Re: Non-working Commodore PET 3016

Quote:
Originally Posted by SiriusHardware View Post
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.
.
I recenty bought a Arduino MEGA256 from a UK supplier on eBay for 10.75 (Its obviously a clone, but works fine) which should be more than OK for testing PROMs. Combine it with a breadboard and some jumper wires and a PROM tester wouldn't be hard.
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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Old 4th Feb 2021, 7:21 pm   #471
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Default Re: Non-working Commodore PET 3016

Quote:
Originally Posted by Slothie View Post

I recently bought a Arduino MEGA2560 clone for 10.75 (Its obviously a clone, but works fine
Not bad at that price. I'm already aware of one or two 'off the peg' EPROM reader sketches which would read one of those PROMs without modification, you'd just need to wire the PROM so it 'looked' like a 2732. Can you confirm that the Mega 2560 is a native 5V device though? I've never had one.

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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Old 4th Feb 2021, 7:23 pm   #472
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Default Re: Non-working Commodore PET 3016

Quote:
Originally Posted by SiriusHardware View Post
Quote:
Originally Posted by ScottishColin View Post

Ever one for a challenge - do these look suitable?

Colin.
I think you may have mislaid a link.
Oops.

https://www.amazon.co.uk/Channels-Co...1&rps=1&sr=8-5
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Old 4th Feb 2021, 7:25 pm   #473
ScottishColin
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Default Re: Non-working Commodore PET 3016

Quote:
Originally Posted by SiriusHardware View Post
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.
Is this the same board? 11 if so.

https://www.ebay.co.uk/itm/Arduino-M...EAAOSwwjVetIEH
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Old 4th Feb 2021, 7:33 pm   #474
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Default 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.
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Old 4th Feb 2021, 7:40 pm   #475
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Default Re: Non-working Commodore PET 3016

Quote:
Originally Posted by SiriusHardware View Post
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.
If I went the Arduino route, does the software already exist in some GPL format that you are aware of?

Thanks.

Colin.
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Old 4th Feb 2021, 7:52 pm   #476
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Default Re: Non-working Commodore PET 3016

Quote:
Originally Posted by ScottishColin View Post
I didn't need to trouble the third hand - the only pins I get a discernible square wave from are pins 1 and 19 of both UE9 and UE10. All others give no reading (with the exception of pin 10 which gives a strange non-square reading on both ICs).
Pin 10 should be ground, if you can check again and confirm then send us a scope view of that.

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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Old 4th Feb 2021, 7:59 pm   #477
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Default Re: Non-working Commodore PET 3016

Quote:
Originally Posted by ScottishColin View Post
If I went the Arduino route, does the software already exist in some GPL format that you are aware of?
Is it not almost as cheap to buy an eprom programmer?

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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Old 4th Feb 2021, 8:01 pm   #478
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Default Re: Non-working Commodore PET 3016

Quote:
Originally Posted by ScottishColin View Post
Quote:
Originally Posted by SiriusHardware View Post
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.
If I went the Arduino route, does the software already exist in some GPL format that you are aware of?

Thanks.

Colin.
I would say its unlikely to find code for a 6540 specifically, but this blog describes it for a 27xxx series IC and could be adapted

https://victorengineeringreloaded.wo...re-extraction/
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Old 4th Feb 2021, 8:02 pm   #479
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Default 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.
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Old 4th Feb 2021, 8:19 pm   #480
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Default Re: Non-working Commodore PET 3016

Quote:
Originally Posted by Mark1960 View Post

Is it not almost as cheap to buy an eprom programmer?

It might be better just to send to someone that can verify the proms for you if there are any volunteers.
How much are EPROM programmers in Canada??

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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