Sega Saturn De-Mux

[Waterbury]

Hi everyone, I know the mux-ing of a Saturn control pad is pretty straight forward but is there an equivalent elegant solution for de-muxing the controller that doesn't involve microcontrollers? Thanx 

[NFG]

You could do it without a microcontroller, I'm sure.  I haven't given it serious thought, but if you REALLY don't want to do it the easy way, you'd need:

1. clock
2. some method of activating the different select lines in sequence
3. A latch to read the four lines from the pad
4. a method for switching to the next latch in sequence
5. goto 2

So your chip count went from 1 to something like 10 and your component count is up to like 30.

Anyone else?

[Waterbury]

That's what I figured. I know you prefer hacking controllers and wiring directly, but do you have any recommendations for a microcontroller that will get the job done that will not produce that much lag?

[NFG]

I don't 'prefer' hacking controllers directly, it's just the easiest for me.  It's also all I really know how to do... 

Despite writing up my first ever chunk of code (in assembly!) for a PIC chip to transcode Saturn pads to SNES output, I've never actually implemented it.  The concepts are easy, I've just never gotten around to trying it...  Soldering wires is just so brain-dead easy, if more expensive and obviously less elegant.

As for lag, I can't imagine anything would have a significant amount of lag.  You only need to do it 60x / second and latch the output to make the system 'fast enough'.  1/60th lag is unlikely to be noticable to anyone, and since that's the fastest your screen could possibly refresh there's no point going faster.

[kyuusaku]

Drew this without trying it, the oscillator may need slight tweaking, but the logic should be fine. Total parts cost should come to under US$0.75.

[l_oliveira]

Thanks so much for the circuit !