[sci.electronics] 74LS is too slow. Maybe?

raoul@eplunix.UUCP (Nico Garcia) (04/24/91)

In article <1991Apr23.013116.3769@nntp-server.caltech.edu>, josephc@nntp-server.caltech.edu (Simplelogic (Joseph)) writes:
> My problem is that a couple of 74LS gates will already add up to about 40ns
> to the access time...  Ergo, wait states - something that I don't want
> to have if I can get away without it.

Hmmm. I don't know how the clever digital people did it, but what's
the net delay on a PAL down to these days? Also, can you cleverly
run your gates off the previous clock cycle or the latter half of
it? It's a bit of a kludge, but it might work....


-- 
			Nico Garcia
			Designs by Geniuses for use by Idiots
			eplunix!cirl!raoul@eddie.mit.edu

lpdjb@brahms.amd.com (Jerry Bemis) (04/25/91)

In article <1067@eplunix.UUCP> raoul@eplunix.UUCP (Nico Garcia) writes:
>In article <1991Apr23.013116.3769@nntp-server.caltech.edu>, josephc@nntp-server.caltech.edu (Simplelogic (Joseph)) writes:
>> My problem is that a couple of 74LS gates will already add up to about 40ns
>> to the access time...  Ergo, wait states - something that I don't want
>> to have if I can get away without it.
>
>Hmmm. I don't know how the clever digital people did it, but what's
>the net delay on a PAL down to these days? Also, can you cleverly
>run your gates off the previous clock cycle or the latter half of
>it? It's a bit of a kludge, but it might work....
>
>
>-- 
>			Nico Garcia
5nS PALs are out these days.  Call AMD at 800 222-9323

henry@zoo.toronto.edu (Henry Spencer) (04/27/91)

In article <1991Apr23.013116.3769@nntp-server.caltech.edu>, josephc@nntp-server.caltech.edu (Simplelogic (Joseph)) writes:
> My problem is that a couple of 74LS gates will already add up to about 40ns
> to the access time...  Ergo, wait states - something that I don't want...

The original article of this hasn't wandered into zoo yet -- either we've
got a propagation glitch or it had illegal headers and never made it --
but insofar as I understand the problem out of context, have you considered
a faster TTL family like 74F?  74F is probably going to be less hassle
than getting something like a PAL blown.
-- 
And the bean-counter replied,           | Henry Spencer @ U of Toronto Zoology
"beans are more important".             |  henry@zoo.toronto.edu  utzoo!henry