Re diagram : so, there *is* a use for PNP transistors, after all! ;-) This also avoids having to rush to set the 8255 mode to output, but all leds will turn on for a µS when use set the mode to output, followed by FF to turn them all off.

I would suggest using a 273-type latch for outputs. It has a clear function (reset), & the o/ps stay at 0 till you say otherwise.

For the inputs on portA, don't forget the pull-ups & the mode word (or don't use any - 8255 defaults to inputs on reset - er, you do reset the chip, I suppose!).

Again, I would suggest the 244 as an input device. OK, so you need 4 chips (3x244/273, 138) to replace the 8255, but think about the layout flexibility! & SMD too!

Regards,

Richard.be