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Old 8th Apr 2021, 6:45 pm   #1442
ortek_service
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Join Date: May 2018
Location: Northampton, Northamptonshire, UK.
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Default Re: Non-working Commodore PET 3016

It hadn't originally really mattered (to me at least) that the 2 channels being chosen each time weren't from either side of the buffers, as I'd thought these were only active when RAM was being accessed.

However, I now see that even when not read-enabled, they will be for writing
- Hence the need for further cascaded Buffers on Main & Video-RAM.
And this does makes these much easier to check, at least.

I had gone through all the originally-captured signals, and found that the first ones shouldn't have been possible, with no activity on some CPU Databus lines.
But the 2nd set had made much more sense, and I'd summarised them all in a table, also observing the odd approx 0.5V level on lines D4 & D5 - Although ONLY on the CPU-side, on the ones I looked at.

I tried to paste the text file below, but it looks like you can't get tabs / spaces to work right here, so have attached this.

And I now suggest re-capturing:
U10-2(or3) alongside U10-19 on other channel
U10-4(or5) alongside U10-19 on other channel

- That way it can be seen if the odd level is a conflict during a read or a write.




2nd Boot:

Memory-Bus Side CPU-Bus Side
--------------- ---------------
Line UE Pin Levels / duty (L:H) Line UE Pin Levels / duty (L:H)
BD0 9 18/17 p17: 0V&4V Var.-burst D0 9 2/3 p3: 0V&4V Var.-burst
BD1 9 16/15 p15: 0V&4V Var.-burst D1 9 4/5 p5: 0V&4V Var.-burst
BD2 9 14/13 p13: 0V&4V Var.-burst D2 9 6/7 p7: 0V&4V Var.-burst
BD3 9 12/11 p11: 0V&4V Var.-burst D3 9 8/9 p9: 0V&4V Var.-burst
BD4 10 18/17 p17: 0V&4V Var.-burst D4 10 2/3 p3: 0V&0.5V&4V Var.-burst **
BD5 10 16/15 p15: 0V&4V Var.-burst D5 10 4/5 p5: 0V&0.5V&4V Var.-burst **
BD6 10 14/13 p13: 0V&4V Var.-burst D6 10 6/7 p7: 0V&4V Var.-burst
BD7 10 12/11 p11: 0V&4V Var.-burst D7 10 8/9 p9: 0V&4V Var.-burst


1st Boot:

Memory-Bus Side CPU-Bus Side
--------------- ---------------
Line UE Pin Levels / duty (L:H) Line UE Pin Levels / duty (L:H)
BD0 9 18/17 p17: 0V&4V 60:40 D0 9 2/3 p3: 0V&4V 60:40
BD1 9 16/15 p15: 0V ***** D1 9 4/5 p5: 0V *****
BD2 9 14/13 p13: 0V&4V 25:75 D2 9 6/7 p7: 0V&4V 70:30
BD3 9 12/11 p11: 0V&4V 30:70 D3 9 8/9 p9: 0V&4V 30:70
BD4 10 18/17 p17 0V&4V 60:40 D4 10 2/3 p3: 0V&4V 60:40
BD5 10 16/15 p15: 0V&4V 60:40 D5 10 4/5 p5: 4V *****
BD6 10 14/13 p13: 3.5V&4.5V 60:40 ** D6 10 6/7 p7: 3.5V&4.5V 70:30 **
BD7 10 12/11 p11: 0V&4V 60:40 D7 10 8/9 p9: 0V&4V 60:40
Attached Files
File Type: txt UE9&UE10_BufferLevels.txt (1.3 KB, 29 views)
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