On 7/1/20 11:21 PM, Gerhard Hoffmann wrote:
Am 02.07.20 um 00:35 schrieb jimlux:
On 7/1/20 1:41 PM, ed breya wrote:
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
16 bore holes just to deploy 4 flip flops is not what I'd call
simplicity. And Fairchild
recognized that as well. The 390 did not make it into the 1987 Fairchild
Advanced CMOS
(FACT) data book.
They expected other chips to sell better, like the 74ACT488 GPIB / HPIB
/ IEEE488 bus
interface. Ever used one? The market for Nixie clocks with one counter +
one decoder
per digit must have been smaller, even back then.
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.
That's sort of the design goal for the 22V10 and earlier PAL devices -
keep them in familiar DIP packages, power on the corners like the IC
gods intended, and you can program it to replicate a whole variety of
MSI functionality, often with the same pinout.
Corner pinning for Vcc and GND is not what any gods intended. In FACT,
(pun intended)
it's evil. Remember ground bounce? The corners are the worst locations
on a DIL chip
you can find for that job. And fig leaf capacitors across the chip are
just that.
Certainly, but when wire wrapping that big panel, and using a different
color of wire for the V+ and V-, it sure makes it easier. <grin>
At 100 MHz, they simply are not there. The optical illusion helps only
to hide that.
The 3 ACT chips on the experiment board posted yesterday reminded me of
the
last pages of this:
<
http://www.hoffmann-hochfrequenz.de/downloads/experiments_with_decoupling_capacitors.pdf
>
The golden times of logic design are now, not then!
I'm surprised nobody has suggested using the 12AX7 or 6J6 dual triodes.
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