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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, 10:18 pm   #481
Mark1960
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Default Re: Non-working Commodore PET 3016

Cheapest that seems capable of bytewide memory rather than only spi seems to be this g540,
https://www.amazon.ca/NKTECH-Univers.../dp/B075625DW5

The tl866 seems more popular, but approx CAD$120, I think these can read the older eproms, but may not be able to provide the higher 25v programming voltage.

Mine is gq4x4, from Canadian supplier.
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Old 4th Feb 2021, 11:22 pm   #482
SiriusHardware
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Default Re: Non-working Commodore PET 3016

Thanks for that, Mark.

I've actually ordered a Mega clone myself - been needing an excuse for a while, plus some of those FET based level shifters which I had not actually seen before.

As well as the task of verifying the PROMs, is there anything more we can suggest looking at on the purely electronic side? The lack of activity on either side of the data bus buffers sounds strange, as does the odd signal on what should be the data buffer 0V pins (pin 10 of each IC).
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Old 5th Feb 2021, 12:48 am   #483
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Default Re: Non-working Commodore PET 3016

I am reading but, we are missing something on the Data Buffer - there must be traffic for the CPU to generate address line changes...
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Old 5th Feb 2021, 3:57 am   #484
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Default Re: Non-working Commodore PET 3016

The 6502 doesn’t need to receive correct instructions to show activity, it just needs to not receive the kil instructions due to the corruption.

I think the pin 10 of the buffer lack of ground is important to investigate. Then after that try again to measure the data bus on each side of the buffer.

I think this needs to be done before worrying about verifying the proms, which might require an eprom programmer or building an eprom reader.
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Old 5th Feb 2021, 9:08 am   #485
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Default Re: Non-working Commodore PET 3016

Well then, if Colin can first check that the pin 10s of the two address buffers UE9 / UE10 both have continuity to a known good 0V we'll take it from there.
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Old 5th Feb 2021, 9:44 am   #486
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Default Re: Non-working Commodore PET 3016

Quote:
two address buffers UE9 / UE10
... I meant DATA buffers of course.
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Old 5th Feb 2021, 10:41 am   #487
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Default Re: Non-working Commodore PET 3016

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Originally Posted by Mark1960 View Post
before worrying about verifying the proms...
As I mentioned, if Colin is amenable to letting them out of his sight for a few days I would be happy to read them and compare them against the files available on the internet.

I have a feeling we are going to have to allay that doubt, by some means, at some point.
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Old 5th Feb 2021, 11:39 am   #488
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Default Re: Non-working Commodore PET 3016

I have just come up with an idea that will cost the price of a couple of ZIF sockets and the inverter as that is more or less what I saved them for.
Your host machine would need a parallel port to talk to a Z80 PIO.
The programmer is untested but does have locally generated programming voltage.
I have already posted photos.
https://www.vintage-radio.net/forum/...d.php?t=173983
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Old 5th Feb 2021, 12:11 pm   #489
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Default Re: Non-working Commodore PET 3016

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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.
UE9 and UE10 pin 10 to my 0V point (UG4 pin 8) - all readings are either 0V or -0V

Scope tests of UE9 and UE10 pin 10 attached.

https://drive.google.com/file/d/1FuR...ew?usp=sharing

Colin.
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Old 5th Feb 2021, 12:16 pm   #490
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Originally Posted by SiriusHardware View Post
Thanks for that, Mark.

I've actually ordered a Mega clone myself - been needing an excuse for a while, plus some of those FET based level shifters which I had not actually seen before.

As well as the task of verifying the PROMs, is there anything more we can suggest looking at on the purely electronic side? The lack of activity on either side of the data bus buffers sounds strange, as does the odd signal on what should be the data buffer 0V pins (pin 10 of each IC).
fyi - I've just ordered the level shifters and the Arduino too as I like to experiment.

My intent is to use the Pi to examine the ROM as I'm more familiar with that but it's probably time I did something Arduino.

They turn up on Monday so nothing doing over the weekend with the ROMs.

Colin.
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Old 5th Feb 2021, 12:19 pm   #491
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Default Re: Non-working Commodore PET 3016

Quote:
Scope tests of UE9 and UE10 pin 10 attached.
That still seems to indicate a significant resistance between your scope ground and those pins. (You should really just have a flat line). What resistances do you see if you measure from UE9 pin 10 / UE10 pin 10 to UG4 pin pad 8? (power off, of course).
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Old 5th Feb 2021, 12:20 pm   #492
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Default Re: Non-working Commodore PET 3016

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Originally Posted by SiriusHardware View Post
Quote:
Originally Posted by Mark1960 View Post
before worrying about verifying the proms...
As I mentioned, if Colin is amenable to letting them out of his sight for a few days I would be happy to read them and compare them against the files available on the internet.

I have a feeling we are going to have to allay that doubt, by some means, at some point.
So here's my thoughts if that's OK.

I mentioned a while back there was a 'spare' ROM with the PET that seems redundant. It's unmarked and was never in a socket.

I'll keep that one for me to experiment with reading via the Pi.

And I'll package the others up and send them to you for reading/checking if that's OK? I think it'll take me too long to work through how to get some python up and running with the Pi to be useful, but I can experiment with the 'spare' one.

Colin.
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Old 5th Feb 2021, 12:21 pm   #493
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Unhappy Re: Non-working Commodore PET 3016

Quote:
Originally Posted by SiriusHardware View Post
Quote:
Scope tests of UE9 and UE10 pin 10 attached.
That still seems to indicate a significant resistance between your scope ground and those pins. (You should really just have a flat line). What resistances do you see if you measure from UE9 pin 10 / UE10 pin 10 to UG4 pin pad 8?
I get readings of either 0.000 or -0.000 with red/black probes either way round.

Colin.
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Old 5th Feb 2021, 12:52 pm   #494
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Default Re: Non-working Commodore PET 3016

Quote:
Originally Posted by Refugee View Post
I have just come up with an idea that will cost the price of a couple of ZIF sockets and the inverter as that is more or less what I saved them for.
Your host machine would need a parallel port to talk to a Z80 PIO.
The programmer is untested but does have locally generated programming voltage.
I have already posted photos.
https://www.vintage-radio.net/forum/...d.php?t=173983
No parallel ports here. On any of my multiple PCs. That's a thing I hadn't even noticed until your post.

I will now go and mourn parallel ports, along with 25 pin serial ports.

Colin.
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Old 5th Feb 2021, 1:01 pm   #495
SiriusHardware
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Default Re: Non-working Commodore PET 3016

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Originally Posted by ScottishColin View Post
And I'll package the others up and send them to you for reading/checking if that's OK?
Yes, no problem, I will PM you this evening about that (we don't put personal details / emails / telephone numbers in forum posts here).
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Old 5th Feb 2021, 1:26 pm   #496
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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
And I'll package the others up and send them to you for reading/checking if that's OK?
Yes, no problem, I will PM you this evening about that (we don't put personal details / emails / telephone numbers in forum posts here).
I understand - thanks.

Does this look like a good place for me to start with the Pi?

https://www.instructables.com/Raspbe...OM-Programmer/

Colin.
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Old 5th Feb 2021, 3:47 pm   #497
SiriusHardware
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Default Re: Non-working Commodore PET 3016

I haven't had time to look at the actual code but in principle it looks OK.

I'm not happy about the bit where he says to run the device on 3V3 - if the target device (or device to be read) can actually run on a range of voltages, then that's fine but I suspect your old PROMs are likely to be very keen on having a 5.0V supply, so you'll have to run them on 5V and use level shifters at least between the PROM databus and the Pi inputs. You might get away with using 3V3 outputs to drive the address and CE and _CE pins on the PROM.
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Old 5th Feb 2021, 3:59 pm   #498
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Default Re: Non-working Commodore PET 3016

In the circumstances I would put level shifters on all the pins. We don't want to introduce another unknown and muddy the waters further.
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Old 5th Feb 2021, 5:30 pm   #499
SiriusHardware
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Default Re: Non-working Commodore PET 3016

That's a fair argument, I think Colin has ordered enough level shifters to handle all of the address, data and CE lines in any case.
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Old 5th Feb 2021, 6:12 pm   #500
SiriusHardware
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Default Re: Non-working Commodore PET 3016

Just had a quick look at the code in the article linked to in #496 - the code looks like a good core starting point for an eprom reader although as written it prompts you for a single binary address to read and outputs the data read from that one address in 'ASCII binary', if I have correctly understood it.

You'd need to put a counter loop around that so that it reads all the addresses from 0 to 4095 inclusive and maybe arrange it to output the byte values as Hex(adecimal) rather than as binary, and possibly as ASCII as well because that will show you any plain text it finds - in the BASIC PROMs especially there is likely to be quite a bit of plain text.

If you've bought an Arduino Mega or clone then quite honestly the Arduino sketch in the article which Slothie pointed to in #478 is virtually oven-ready, you'd just need to alter the number of bytes it reads down to 4096, otherwise it is just about ready to go.
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