GAL16V8 as a modern substitute for a 7447?

[Bob Armstrong]

>Ethan Dicks [ethan.dicks at usap.gov] wrote:
>Thanks for any nudges towards a solution.

  Implementing the combinatorial logic for a seven segment decoder is
trivial even for the simplest GAL.  But, as somebody else pointed out, the
latches in a simple GAL are permanently tied to output pins, so a 4 bit
counter plus a seven segment decoder would need 4+7=11 output pins.  A 16V8
has only 8 outputs, and a 22V10 has only 10, which rules both of them out.

  Now if you only wanted it to latch the data rather than count, that'd be
possible with a 16V8.

  Hmm...  Having said all that, it might be possible to put a state machine
into a 16V8 that had a 7 bit current state and a next state function that
corresponded to "counting" is seven segments.  In theory that'd work, but I
don't know off hand if there are enough terms inside a 16V8 to implement
that next state function.  I'll leave that as an exercise for the reader :-)

  Another thing to keep in mind is that parts like these are really power
hungry, even compared with traditional 74xx parts.

> Ethan Dicks, A-333-S     Current South Pole Weather at  8-Dec-2007 at
15:40 Z

  Are you back down there again??  Did you see the NBC news team that
visited a few weeks ago?

Bob