ive got one of these in my modular which is a key to almost every pathc i make.
i was just hunting about for schematics cos im about to stick one into my 80s yamaha pc100 keyboard to divide down the main clock. its all internal so i dont need as much buffering to the outside which is nice.
i dont need reset either but i just want to know: what the hell is up with that crazy reset circuitry?
If i remember correctly the logic high levels are dependent on the supply voltage.
My guess is the reset circuitry is there to accommodate for gate voltages lower than Vdd.
Itās just two cascaded inverting stages, biased by the the other transistor.
Also the rise time will be faster with higher input levels
Itās original design was made by Mathias Herrmann for his inspiring Fonitronik. However, his design gives inverted outputs, which I changed to normalized outputs. Also I added a start-up reset pulse, to ensure that all outputs are low when the modular is started.
So the ābias circuitā is actually that startup pulse: When power is applied, the center left transistor turns on and kicks the reset input. The rest is a pair of inverting buffers to condition the input pulses, as said.