I'm trying to understand the Apple 1, Terminal section, circuit operation. I ran across a pretty good description of parts of it at:
However, it doesn't explain in detail the timing / control signal generation. So I'm trying to do that myself. I've figured out that D6 and D7 count out 165 character timeslots for each horizontal scan line, and that D8 counts 8 scan lines per character row, and part of the character row count, along with D9. At some point in the vertical row count, D8 and D9 are preset (to F and B respectively?), altering the count sequence in such a way as to be able to count 262 scan lines, or 32.75 character rows before the vertical count sequence repeats itself.
Where I'm stuck is understanding what the signals NOT WC1 and NOT WC2 represent. I need to know about NOT WC1 because it is involved (as an input to C9) in determining when the preset inputs to D8 and D9 go low, presetting these counters.
Signal VINH, generated by D15, is also involved in the vertical row countdown process somehow, but I haven't spent much time on it yet, since I got stuck on WC1.
I did notice what seems to be an error (or probably something I've missed) in that VINH is generated at D15, pin 13, but it's inverse, NOT VINH, appears as the CEP input to D8 and D9, but I don't see any circuitry inverting VINH to NOT VINH anywhere.
Can anyone help me with these questions?