On Jan 19, 7:17*am, "Arfa Daily" wrote:


So I have a good look at what's in it. *2 x 4027 dual J-K, *3 x 4011 quad
NAND, * 2 x 4081 quad AND,
*1 x 4040 12 stage counter, * 1 x 4020 14 stage counter, * 1 x 555 timer and
last but not least, 1 x MK50395 decoder / driver. *Now I don't know if I'm
just being dumb-arsed here, or having a senior moment, but I'm buggered if I
can see any chips in that line up that could form a memory and comparator
for potentially 99999 numbers. Or even for 90 numbers come to that ... If
this is what it was meant to do, even back in '81, I would have expected to
see a couple of CMOS memory chips, and a Z80 or *8080 processor, maybe.

First, a caveat. It's been nearly 20 years since I drifted away from
digital hardware design to the dark arts of software. That said....

The 555 and the counters must be part of the logic to _generate_ the
random number, based on randomly stopping the counters with the button
push, the other stuff looks like it would be used for "glue" logic for
the counters, and comparison for the start and stop numbers. You're
right, I don't see anything that would serve as a memory to be used to
check for duplicates.

I think what you have is just a random number generator, and the
"memory" was a paper-and-pencil operation.

Jerry