Tom wrote:
"Ed, For division, there's less need for a dedicated divide-by-10
counter since the '161 and '163 are *presettable* synchronous binary
counters. As such you can wire them to divide by anything from 2 to 16,
which includes 10. In addition they are *cascadable*, which means that
you can create synchronous 8- or 12- or 16- or 20-bit or even larger
dividers. The datasheets for these counters sometimes show examples of
multi-chip dividers. Attached is a photo of a 'LS00 plus 3 'LS161
counters configured as divide-by-1173 counter. The 2nd photo is a
divide-by-3295 count. You can see it's just a matter of changing the
jumpers on the preset pins.
/On 6/29/2020 3:32 PM, ed breya wrote:Looks like the AC161 and AC163 are
readily available, so they may be />/rigged for divide 5. It seems that of the counters surviving into AC, />/only binary ones are included, and the oddballs like decade are />/considered unnecessary - apparently nobody divides by 10 anymore, />/except inside of a processor."/
Yeah, I know. I was just lamenting the lack of nice medium-density count
functions in 74AC. It's hard to beat the simplicity of a '390 when you
want divide 5s and 10s, having two complete bi-quinary counters in one
package, ready to go. I've used HC390s and 393s often for up to 20 MHz,
and always assumed I could get the AC versions if needed, although I
usually go with ECL above that anyway, so this issue never came up for me.
I haven't looked at my 74AC parts inventory in a while, but I think I
may have a couple '390s or '393s - I guess I'll have to hang on to them
for "special" occasions. One thing I found interesting in my recent
searching for AC parts, is that the AC4040 is available. That's my
favorite counter for dividing by big numbers, good for any integer to
4095, in one package, plus some simple external diode or glue logic
feedback.
Anyway, I've always liked having a wide assortment of MSI logic devices
available in all families, that you just hook up and it goes - no setup,
no programming. I've saved lots of counter types for possible use. One
obscure one is the MC14566, with divide 6 counters for clock time
readout and generation, in the old days.
Ed
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