5 Sep
2000
5 Sep
'00
6:36 p.m.
ard(a)p850ug1.demon.co.uk (Tony Duell) wrote:
No. Please don't wire-AND normal TTL outputs -- it won't work properly
all the time. It's marginal (and can damage the TTL chips involved).
There is an open-collector 4-input NAND in the TTL line. It's the 7422
(yes, I had to look it up). You could use one of those, along with a 2k2
(or thereabouts) pull-up resistor from the output to Vcc. Don't ask me
where to find a 7422, though.
Hi
Looks like the 7422 is what I need. I was thinking
this myself. The spec sheet I got says that it has
an internal 2K pullup. The other part also has this
so it should work without an additional resistor.
I can always add one but I would exect it will be
more than fast enough for this old machine.
I hope I can get to my local surplus shop before they close.
Thanks