I'll download that Datasheet. Years ago I vowed to avoid devices with only an SSP module instead of an MSSP module for some reason.

I'm familiar with the '138/'238 and '139 but I've never looked at the '137. Thank you. I'll grab the Datasheet.

This deserves a closer look. Thank you, Klaus.

http://www.alldatasheet.com/view.jsp?Se ... d=74ALS996
8-BIT D-TYPE EDGE-TRIGGERED READ-BACK LATCHES

I've never seen them listed anywhere, though.

_________________
"I am endeavoring, ma'am, to create a mnemonic memory circuit... using stone knives and bearskins." -- Spock to Edith Keeler

http://octopart.com/partsearch#!?q=74als996

I guess they're easier to find than you thought

===Jac

I use a 573 in my Orwell machine as a simple addressable 8 bit latch. I have eight LEDs on it and use it for debugging (and doing silly Larson scanner things). There was just a little logic needed to handle the positive chip select and I think from memory I just address decode it the same as if it were normal RAM (so phase 2 is involved). I can check when I get home. It seems to work fine but maybe that's because I am running slowly, only 1Mhz, so the timing just works.

Simon

_________________
My 6502 related blog: http://www.asciimation.co.nz/bb/category/6502-computer

If you want an output port whose contents you can read back, one very simple solution is to use a '574 but arrange the decoding such that RAM is not inhibited when the port's address appears. I think of this as causing the '574 shadow what's in that bit of RAM. But however you like to think about it, the upshot is...

• writes go to the '574 and RAM
• reads cause the RAM to return the last value written

_________________
In 1988 my 65C02 got six new registers and 44 new full-speed instructions!
https://laughtonelectronics.com/Arcana/ ... mmary.html