28 Oct
2010
28 Oct
'10
12:07 p.m.
As a pure ROM, you may be thinking of the MC4039,
which, by
Motorola's admission, was nothing but a preprogrammed version of the
XC170 128-bit mask ROM. Circa 1969.
If you ingnroe 'progammable' devices (PROMs, PALs, FPGAs, etc), what's
the simplest solution for getting 0-9,A-F from 4 bits of binary using
only 74xxx devices (and preferably common ones). I can trivially do it
in 7 such chips, but alas they're all 24 pin devices. Anything simpler?
The same ROM was used as the MC4001 BCD-to-Binary/Binary-to-BCD
encoder.
I beleive the 74184/74185 BCD<->binary converters were programmed
ROM/PROMs too. And as an aside, there were some MMI logic chips, things
like counters with extra facilities, which were clearly programmed PALs/HALs.
-tony