Bob Ammerman asked:

2: what family/families are best for general purpose digital design -
especially around a PIC (this is the PICLIST!).

I would say the 4000 and 74HC series are most usefull. Operation at extre=
me
speed might occasionally call for faster devices. 74HCT has some
applications.

4000 type: Readily available, low cost, contains a number of usefull anal=
og
functions including the 4007 triple complementary pair+inverter, one of t=
he
few devices to feature mosfets with the substrate not connected to the
source. Voltage range not a good match to the PIC, not sure whether it
would work at 3v. Slow speed can be an advantage in mixed signal circuits=

as supply noise is low. 4049/4050 buffers accept inputs above the supply.=


74HC: Readily available, costs more than 4000, some analog functions whic=
h
will have much lower on resistances than equivalent 4000. Faster (not
always an advantage). Supply range supposed to be 2v to 6v so exceeds PIC=

in both directions.

74HCT: Variant of HC with lowered input thresholds, when powered from 5v
should accept signals from 3v logic.

Various 'low voltage logic' families have sprung up to operate from
3.0v-3.5v but a PIC circuit is unlikely to require the higher speed so 74=
HC
should be adequate. Some of the new devices accept inputs above the suppl=
y,
and some will even allow a tristated output to be pulled above the supply=

(most CMOS will not like this).

There is also a family of digital switch devices (pass transistors) which=

would be of little interest except they offer a very simple way of
interconnecting different logic levels. =