Dec 8235 IC?
pete at dunnington.plus.com
Thu Sep 3 04:29:56 CDT 2015
On 03/09/2015 09:05, simon wrote:
> is there a list of equivalents for DEC ic's?
> I've made a mistake in attaching our BA-8 to the PDP8/f and twisted the
> ribbon cable connecting connector C and D. some magic smoke came loose
> and there are a few chips broken . :-(
I don't have a list, but I do have a copy of the 1976 Signetics ICs
databook, which lists a lot of 82xx logic. I've not checked one of my
M8330 boards but I guess that's what you need.
8235 is a quad (4-bit) 2-input multiplexer - with a twist. It has open
collector outputs and two control inputs. The twist is that one of each
pair of inputs is non-inverting, the other is inverting, and the idea is
that by tying the two inputs together you can use the control inputs to
make the outputs the TRUE or COMPLEMENT of the input data, eg to feed to
The data sheet is two pages, which I can scan if you want.
The An and Bn data inputs are pins 1 and 2, 6 and 5, 10 and 11, 15 and
14; corresponding f0 to f3 outputs are pins 3, 4, 12 and 13. S0 and S1
are pins 9 and 7. Vcc is pin 16, GND is 8.
S0 S1 fn
---- ---- ----
0 0 /An.Bn
0 1 Bn
1 0 /An
1 1 1
I like the last paragraph of the description. "The 8234 and 8235
designs have open collector outputs which permit direct wiring to other
open collector outputs (collector logic) to yield 'free' four-bit words.
As any as one hundred four bit words can be multiplexed by using up to
fifty 8234/8235 in WIRED-AND mode."
Good thing DEC didn't go quite that far.
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