All the PIn 20s seem to be driven from UD2 pins 14,15,16,17 (Sheet 1 of the schematics).
Should I see continuity from those pins to pins 20 on UD6/7/8/9 when the power is off - or do they only get continuity when something actually happens in UD2?
Colin.
Quote:
Originally Posted by dave cox
I think you proved earlier that the CPU was running through the whole address range (activity on A0-A15) so the PROM UD6 *should* be selected (pin 20 low) at some point. I would be following the pcb trace/continuity from UD6/20 back to whatever drives it - it will some kind of address decoder, but i can't find a handy schematic to go further !
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