PDP-8/L teletype connection

From: David Gesswein <djg_at_drs-esg.com>
Date: Sun May 21 17:50:38 2000

From: Lawrence LeMay <lemay_at_cs.umn.edu>
> The card is a W076 D.
>
> 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?
>
It took me a while to remember where they stuck the schematic for the W076
but I found it. If you get the 8/I maintenance manual from
http://highgate.comm.sfu.ca/pdp8 volume I Figure 5-7 pg 5-16 shows the
schematic for the W076 and the connections to the teletype.
I see that the page was scribbled on, the numbers from top to bottom are
4 6 3 relay- 7 relay+.

> 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?
>
If you get an ASR-33 which wasn't used for a PDP-8 I have instruction
on how to add the reader run relay.

I have used a PC (ok it was an old TI PC, used a different serial port
which supported hardware flow control which I connected to the reader
run signal) to talk to my 8/I, I built an external current loop
converter. If you need more information on this email me, from
later postings it looks like you might have a current loop card for
the PC.

If you get overrun problems it may be due to not having the reader
run signal. The 8/I serial port is not double buffered so it doesn't
have much time (1-2 bit time) to remove the character before it is lost
by the next. If I remember correctly only some things like Focal
couldn't keep up at 110.

David Gesswein
Received on Sun May 21 2000 - 17:50:38 BST

This archive was generated by hypermail 2.3.0 : Fri Oct 10 2014 - 23:33:09 BST