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Mark1960 · 4th Jul 2021, 5:45 am

I was going to try changing the 42 to 4B to see if it made any difference, though looking at the extra code that is executed by the jump to 43 it didn’t look like it would make any difference.

I thought I’d test first to confirm the fault and it powered up correctly as 0000 00. Reset a few times and still ok, then after a while it started to show 0001 CF, intermittently at first but then consistent. By Touching the pins on the 8060 with my finger I could get it to power up correctly. Then narrowed this down to pin 39 by touching the pin with tweezers.

NADS is supposed to be a standard output, but it looks like it might need a pull up resistor to drive the clock on the 74LS395. I’ll take a look with the scope first to get a better understanding of what might be happening.

4th Jul 2021, 5:45 am	#40
Mark1960 Octode Join Date: Mar 2020 Location: Kitchener, Ontario, Canada Posts: 1,294	Re: Multiprocessing SCMPII on MK14 I was going to try changing the 42 to 4B to see if it made any difference, though looking at the extra code that is executed by the jump to 43 it didn’t look like it would make any difference. I thought I’d test first to confirm the fault and it powered up correctly as 0000 00. Reset a few times and still ok, then after a while it started to show 0001 CF, intermittently at first but then consistent. By Touching the pins on the 8060 with my finger I could get it to power up correctly. Then narrowed this down to pin 39 by touching the pin with tweezers. NADS is supposed to be a standard output, but it looks like it might need a pull up resistor to drive the clock on the 74LS395. I’ll take a look with the scope first to get a better understanding of what might be happening.