ASR33 reader

From: Charles <charlesmorris_at_direcway.com>
Date: Tue Apr 15 17:18:01 2003

On Tue, 15 Apr 2003 12:00:01 -0500, Tony Duell wrote:

>Ah. With the PDP8/e and PDP11s, there's a relay wired in series with the
>reader trip magnet (the one on top of the distributor unit at the rear
>right). It allows the computer to start and stop the reader, and in fact
>the read a character at a time. It's partly controlled in hardware, in
>that when the PDP derects an incoming character, it turns off the relay
>(stopping the reader). It's then turned on a again by software
>(presumably after said software ahs read the character).

My TTY *does* have a relay on the reader "powerpack" board which
can be turned on if an XON (DC3, Ctrl-Q) is sent to the typing
unit, and off again upon receipt of an XOFF (DC1, Ctrl-S); it also
latches itself on if the reader's manual start lever is flipped,
until it is pushed to the stop position, or the tape-out contact
opens. Is that the relay to which you are referring?

Are you sure the 8/e actually goes to the trouble of turning
off/on the reader after EVERY character? At 10 cps that's 100,000
uS between characters (60,000 machine cycles on my 8/L)?

Meanwhile I have my 33 apart awaiting new function levers that
trigger the above flow-control options (someone had installed
Ctrl-B and CR instead of the correct Ctrl-S and -Q). Further
reader "tuning" will thus be delayed...

-Charles
Received on Tue Apr 15 2003 - 17:18:01 BST