12 Dec
2010
12 Dec
'10
12:29 p.m.
On 12 Dec 2010 at 15:05, Shoppa, Tim wrote:
With regards to pinouts not everyone even inside a
company had the
same thoughts regarding pin locations for Vcc and gnd. TI did a pretty
good job most of the time putting them at 7 and 14 or 8 and 16 for TTL
which did simplify layout, but there are lots of exceptions even
inside the TTL product space. And sometimes there were good reasons
for the exceptions, other times I think it was just internal
squabbling :-)
...and sometimes differing between sub-families with the same numeric
part number. (e.g. 7486 vs. 74L86).
The idea of which way the gates in package should point also seems to
be an early bone of contention (7400 vs. 7401).
And even the issue of pairing inputs with outputs or placing inputs
on the opposite side of the package for bus-related chips (e.g.
74LS373 vs. 74LS573).
--Chuck