I'm transmitting serial data across a cable to a shift register. I transmit data in discrete packets, where different packets have different bit lengths. The clock frequency is about 20 MHz while transmitting.
When each packet ends, I need to generate a short pulse to latch the shift register. I know a packet has ended when the clock stays low for a few cycles.
What circuit will output this latch signal?
Commenters asked some good questions about timing, so I'll clarify:
- The shortest packet is 800 bits, for a duration of 40 μs minimum.
- Idle time between packets is 10 μs minimum.
- The latch pulse duration must be 10 nanoseconds minimum.