>> Impossible to tell from the description below Roger.
>> Post the schematic
>> John
Not really a schematic, more like a diagram. The address selection on the LS688 wasn't actually implemented on the card. The LS688 was hard wired to recognize "FF". And, the LS244's (U3, U4, U5) were not used. Instead, the LS245's provided on the buffered prototype card were used. Also, the control signals shown on one LS244 (in the diagram) are actually spread out over a number of LS245's as provided on the buffered prototype card. I think there are a total of 5 LS245's used. Oh, and there is a bicolor LED attached to pins 5 and 6 of the LS74 so that I can check the state of the flip-flop visually. I doubt that has anything to do with the problem?
Roger