Quote:
Originally Posted by merlinmaxwell
Almost, 7400 is a quad nand, A=1, B=1 so Q=0, use another of the four to invert the output.
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This is going to be tricky to test as a sub-assembly. In the original circuit, a flip-flop receives square pulses at the drive frequency from one source and an enabling pulse on its CLR pin from another. Complimentary gate drivers meant it was possible to drive them (the gate drivers) without needing to invert the signal to one of them.
The 7400 is an additional complication. If I test drive that circuit with two drive signals at different frequencies (I have two to hand) then Y will only be 0 when the two signals are HiGH simutaneously. It will keep changing state when they are not, and that will still happen when I invert the original output state with another gate.
It sounds like I'm talking myself into realising that I can only test the 7400 circuit with the flip-flop in situ.
Alternatively, I could ask the question,
what's the easiest way to test the 7400 sub-assembly for proof that it's working as designed?
I promised to check each sub-circuit as I build, in order to avoid headaches later. This is really important for the logic board, even if it isn't that complex.