Decided to take a good shot at putting my only S-100 serial board to use.
Figured the place to start was ID'ing the connector pin-outs so I could set
up a cable and begin the process.
Lacking any docs whatsoever, all I could do was trace out the PCB and try
to ascertain what was what. So here's what I've come up with - can +you+
figure out which pin is which?
Board has two outputs, J1 & J2. They are standard 10-pin DIP headers, using
the standard numbering scheme. We'll look at J1; J2 is essentially the
same, but routes to different pins / chips / transistors.
Pin 1 - Col. of 2N3906 (Base is driven by opt. 2 of 1458 - see Pin 7)
Pin 2 - Pin 28 (DB3) of both 1014 & 1015 UARTs
Pin 3 - 1K pull-up to Vcc (12V? Same Vcc as 1458s)
Pin 4 - 150R -> 47R -> Pin 6 w/ XNOR input 1A at 150/47 junction
Pin 5 - n/c
Pin 6 - 47R -> 150R -> Pin 4 w/ XNOR input 1A at 150/47 junction
Pin 7 - 1K2 -> opt. 2 of 1458 (see Pin 1)
Pin 8 - GND
Pin 9 - 1458 opt. 1
Pin 10 - GND
So we have what looks like three (3) each Inputs &
Outputs, plus a Vcc and
GNDs:
Inputs - Pin 2, 4, 6
Outputs - Pin 1, 7, 9
Vcc - Pin 3
Gnd - Pin 8, 10
So.. what do +you+ make of it? =)
Well...
First oddity is pin 2? What on earth is that for? Why bring out one data line with no
enables, strobes, etc?
Are you sure about this?
Now, the 1458 is a dual op-amp. It was commonly used in old serial devices as a level
shifter.
My guess is that pin 7 is an RS232-like voltage output, serial data. Pin i is a current
loop output,
same data.
The receive input has me stumped at this point. I would guess it's pins 4 and 6. Again
possibly current loop.
I would trace out all the circuitry in that area. It is probably possible to connect it
for RS232 input, but
no idea how without the complete circuit.
-tony