16 Nov
2004
16 Nov
'04
1:23 a.m.
>>>> "William" == William Maddox
<wmaddox(a)pacbell.net> writes:
William> Paul Koning wrote:
Tore> But access to a complete array of spares if nessecary. Oh, and
Tore> the CPU is built in TTL logic, so no hard-to-get spares.
> TTL is getting hard to find, especially the more
obscure types
> such as 74S series. (And if the book says they want 74S, it's
> quite possible no other variant will work...)
>
> paul
William> I thought that 74F series parts were generally replacements
William> for 74S parts. Is this incorrect?
It depends.
Some designs depend on parts being "fast enough". Others are more
finicky. If they need "fast enough" then F or LS or ACT series logic
may well work. If they need "just right" then you have a potential
problem.
For example, some people have used 74S00 devices as crystal
oscillators. Those circuits are less likely to appreciate
substitution.
paul