Prepping for the 74165
The 74165 wants a negative going pulse instead of the positive pulse to load the cd4021. Rather than just invert the N1 pulse I’ve been using, I used a spare nand gate to combine N1 with TPB. The shorter pulse (.6 us vs 5 us) leaves a lot more time for shifting. If I get the 1802’s clock up to 3MHZ the gated pulse would come down to 300 us. I’m not sure the AVR could catch that but it doesn’t really have to – it can continue to look for N1 since it waits for the end of it anyway. I think this is going to work well.