> the problem with that is you cant ever count "down" with the ROM part
> IE you cant make a 1 into a 0
> so its a tally style counter

  Actually, it's possible to make an up/down counter with a PROM: see the app notes for Dallas/Maxim's "add-only memory" iButtons for details.  Short description: blown bits starting at one end of memory are credits, bits starting at the other end are debits.
       Jason Harper
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