PDP 8/L console

From: Lawrence LeMay <lemay_at_cs.umn.edu>
Date: Fri May 19 22:31:47 2000

> >From: Lawrence LeMay <lemay_at_cs.umn.edu>
> >My PDP 8/L that I recently acquired, has a cable that i assume is for
> >the console terminal. It has a 9 pin male connector with only pins
> >1 through 6 present. Is this a standard serial connection? This was
> >a papertape based system, so it may have been connected to a teletype
> >ASR 33. Will I need to locate something that can do 110 baud to use
> >as a console?
> >
> If it is the W076 on the other end of the cable it is a teletype.
> It normally runs at 110 baud current loop. You can either create an
> external RS-232 to current loop or make a new W076 to do RS-232.
> If you want to cheat you can reduce the capacitor on the M452 to increase
> the baud rate. The serial port is not double buffered so you may have
> problems with overruns when sending tape images to the 8/L. I think
> the BIN/RIM loader is fast enough but Focal is not. On the teletype the
> data was held off by the reader run signal.

The card is a W076 D.

Unfortunately, I know almost nothing about current loop connections. I
attempted to read the current loop documentation for the Terak's
current loop interface connector, and only confused myself some more...

There are active and passive connections, and apparently these can be
different between transmit and recieve pairs of wire? Is there a
standard convention?

I need to figure out which connections on the W076 are for what 'signal',
so i can trace the wires to the DB-9 connector, and then make some
adaptor cables. Does anyone have that information on the W076? My
books dont list the W076. And which pairs on the W076 are active/passive,
and am i correct in assuming that active pairs on one device connect to
passive on the other end, ie, active supplies the current for the loop?

I would want to connect a Teletype model 33 (assuming the one i'm
supposed to be getting one of these days actually works...). Also,
I would like to be able to connect an IBM to the 8/L, and hopefully
use it to download paper tape images (probably using a rs232/current-loop
interface). Has anyone been using an IBM like this in place of a
ASR terminal?

Any advice?

-Lawrence LeMay
Received on Fri May 19 2000 - 22:31:47 BST