20th Mar 2021, 8:29 pm | #1181 | |
Octode
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Re: Non-working Commodore PET 3016
Is this OK? Pin 8 yellow, pin 9 green.
Colin. Quote:
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20th Mar 2021, 8:38 pm | #1182 |
Dekatron
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Re: Non-working Commodore PET 3016
That is PERFECT and shows that replacing UB2 has fixed the missing BANK SEL signal. So now we have to find the next broken bit, I need to ask you to revisit UG7.
Can you have a look at UG7 pin 11, turn the horizontal trace speed up until you have one cycle of that waveform on the screen, and at the same time capture whatever is coming out of UG7 pin 8. |
20th Mar 2021, 8:42 pm | #1183 |
Octode
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Re: Non-working Commodore PET 3016
UB2-8 looks good.
Now need to check RAS and CAS again. UH1-6, UH1-8, UG1-11, UG7-6, UG7-12 Note the two different sources for RAS, one is for refresh, the other for read and write for bank selected. |
20th Mar 2021, 8:45 pm | #1184 |
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Re: Non-working Commodore PET 3016
I thought we'd better look for the RAM buffer read enable signal as well.
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20th Mar 2021, 8:49 pm | #1185 | |
Octode
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Re: Non-working Commodore PET 3016
Here you go. UG7 11 yellow, 8 green.
Colin. Quote:
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20th Mar 2021, 8:54 pm | #1186 |
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Re: Non-working Commodore PET 3016
We have a read enable signal on the RAM buffer although I think I expected it to be a series of short pulses, not a steady low like that.
Can you do the ones Mark mentioned, and then I have another one in the queue. |
20th Mar 2021, 8:58 pm | #1187 |
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Re: Non-working Commodore PET 3016
After you've done Mark's checks could you let us see UG7 pin 11 (one complete cycle as before) and this time UG7 pin 9 on the other trace.
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20th Mar 2021, 9:00 pm | #1188 | |
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Re: Non-working Commodore PET 3016
Quote:
Edit: Ignore this, I think it should be steady low. |
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20th Mar 2021, 9:02 pm | #1189 |
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Re: Non-working Commodore PET 3016
I hope you're right, I would have expected it to score a few random hits though. Thinking possibly buffered R/W (UG7 pin 9) may be constantly high, which it should not be of course. Or shouldn't it? That's the default state for the R/W line when it is not writing. We have the CPU locked in read mode while doing the NOP test, so R/W steady high (therefore UG7 (8) steady low) may actually be OK.
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20th Mar 2021, 9:05 pm | #1190 |
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Re: Non-working Commodore PET 3016
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20th Mar 2021, 9:08 pm | #1191 |
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Re: Non-working Commodore PET 3016
Attached. UG7/6 and UG7/12 'pulsed' between high and waves - I've tried to show what my scope shows with the attached files.
Colin. |
20th Mar 2021, 9:08 pm | #1192 |
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Re: Non-working Commodore PET 3016
UG7/12 attached.
Colin. |
20th Mar 2021, 9:09 pm | #1193 |
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Re: Non-working Commodore PET 3016
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20th Mar 2021, 9:10 pm | #1194 |
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Re: Non-working Commodore PET 3016
Confirmed steady high - measured at 5.3V with a meter.
Colin. |
20th Mar 2021, 9:18 pm | #1195 |
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Re: Non-working Commodore PET 3016
The intermittent nature of the signal you had in #1191 was down to the fact that those signals are probably (intentionally) only active for part of the address sweep. I think that's more activity than we had before though?
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20th Mar 2021, 9:26 pm | #1196 |
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Re: Non-working Commodore PET 3016
From #1191 and #1192, CAS0 and CAS1 look correct.
But nothing on RAS0. Check UH1-3 and UH1-1, both together if possible. Also UH1-11 and UH1-13. |
20th Mar 2021, 9:28 pm | #1197 |
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Re: Non-working Commodore PET 3016
I've had a quick look and I don't think I've looked at those pins before?
Colin. |
20th Mar 2021, 9:31 pm | #1198 |
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Re: Non-working Commodore PET 3016
Maybe not those pins, but those signals, probably at the RAM end the last time we looked.
Added to Mark's checks in #1196, can we also see UH1 (8) and UH1 (6) both at the same time as well please. |
20th Mar 2021, 9:34 pm | #1199 |
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Re: Non-working Commodore PET 3016
Attached.
Note UH1-3 was also alternating between the waves shown and a high reading. Colin. |
20th Mar 2021, 9:37 pm | #1200 |
Octode
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Re: Non-working Commodore PET 3016
Less to see on this one...
Colin. |