bonxer said:
Two things: Yes, debouncing matters. It doesn't matter how fast or hard you press your switch or button, there is bounce, and it switches between on and off dozens of times.
Yes, which is actually fine with me. In this particular application, even manually pressing it dozens of times is ok and does not affect operation.
Also, you say that you do not want the latch to reset. So why to you have the switch connected to the /MR (master reset) ?
Because the operation table is as follows:
MR=H LE=H Do nothing, preserve last state
MR=L LE=L Demultiplex (what I want)
MR=H LE=L Addressible latch (I don't want this)
MR=L LE = H Reset chip
So you see, I absolutely have to pull down MR _and_ LE in order to get it into that mode. If I only manipulated latch enable, I'd have to dial up the previous address that was active, set data to zero, hit LE, dial up new address, set data to 1, hit LE again, etc.
Just for a bit of background, the project is a 32 camera multiplexer. On the remote control, one holds down 3 bits representing cam 0-7 then presses one of four bank select buttons. It's those bank select buttons that send MR and LE low, telling the chip to latch onto the appropriate camera and stay there. Of course one has to hold those 3 bits with one's fingers until MR and LE go back high, which is ok with me. Everything does work beautifully with that kludgy RC circuit on the one pin. But the voltage is so low I _really_ need to do it "right" before soldering everything down forever.