4th Feb 2021, 11:18 pm | #481 |
Octode
Join Date: Mar 2020
Location: Kitchener, Ontario, Canada
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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. |
5th Feb 2021, 12:22 am | #482 |
Dekatron
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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). |
5th Feb 2021, 1:48 am | #483 |
Octode
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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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5th Feb 2021, 4:57 am | #484 |
Octode
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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. |
5th Feb 2021, 10:08 am | #485 |
Dekatron
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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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5th Feb 2021, 10:44 am | #486 | |
Dekatron
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Re: Non-working Commodore PET 3016
Quote:
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5th Feb 2021, 11:41 am | #487 |
Dekatron
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Re: Non-working Commodore PET 3016
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. |
5th Feb 2021, 12:39 pm | #488 |
Dekatron
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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 |
5th Feb 2021, 1:11 pm | #489 | ||
Octode
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Re: Non-working Commodore PET 3016
Quote:
Scope tests of UE9 and UE10 pin 10 attached. https://drive.google.com/file/d/1FuR...ew?usp=sharing Colin. |
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5th Feb 2021, 1:16 pm | #490 | |
Octode
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Re: Non-working Commodore PET 3016
Quote:
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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5th Feb 2021, 1:19 pm | #491 | |
Dekatron
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Re: Non-working Commodore PET 3016
Quote:
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5th Feb 2021, 1:20 pm | #492 | |
Octode
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Re: Non-working Commodore PET 3016
Quote:
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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5th Feb 2021, 1:21 pm | #493 | ||
Octode
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Re: Non-working Commodore PET 3016
Quote:
Colin. |
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5th Feb 2021, 1:52 pm | #494 | |
Octode
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Re: Non-working Commodore PET 3016
Quote:
I will now go and mourn parallel ports, along with 25 pin serial ports. Colin. |
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5th Feb 2021, 2:01 pm | #495 |
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Re: Non-working Commodore PET 3016
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5th Feb 2021, 2:26 pm | #496 | |
Octode
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Re: Non-working Commodore PET 3016
Quote:
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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5th Feb 2021, 4:47 pm | #497 |
Dekatron
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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. |
5th Feb 2021, 4:59 pm | #498 |
Tetrode
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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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5th Feb 2021, 6:30 pm | #499 |
Dekatron
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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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5th Feb 2021, 7:12 pm | #500 |
Dekatron
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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. |