4 Nov
2011
4 Nov
'11
4:42 p.m.
On Nov 4, 2011, at 6:42 PM, Tony Duell wrote:
And I think (without checking the databooks) that 4000
series will stand
a higher supply voltage thea 74HCxxx
My recollection is that the 74HCxxxxx are nominal 5V parts (the HCT ones specifically run
with TTL switching thresholds). CD4000 series is full range, I think usually 3.3-15v or
thereabouts, with the switching threshold usually at 0.5Vdd.
74HC was generally considerably slower than 74F for the same part (though also took WAY
less power), 74HCT slower still.
They are slow, and thus are not commonly used in
classic computers. The
odd oens do turn up, particualrly where speed is not very important but
he function was (IIRC ,the BCD interface for my HP9815 calculator has
some odd 4000 series shift registers in it, there is no direct TTL
equivalent,
And I sure love the 405x series of (basically) analog multiplexers and 4016 analog
switches. By now there are a number of better analog multiplexers and switches out there,
but there weren't any straight TTL muxes that I remember which operate in both
directions (because they were typically combinational logic instead of pass gates).
- Dave