11 May
2001
11 May
'01
2:17 a.m.
"Fred Cisin (XenoSoft)" wrote:
On Thu, 10 May 2001, Megan wrote:
This is also the quickest way to connect a TTY (20ma) to modem (RS-232);
by using a computer (PC) in the middle. Both schemes require a little
software. In the case of a tape reader, you must poll the 20 ma port and
when
data is on it transfer it to the serial port (one way). In the case of the
latter
(TTY/modem), you have to poll both ports and when data is present, send it
to the other port.
Both schemes are byte oriented but work as line buffers due to the nature of
the way devices operate.
Eric
I have an old serial paper tape reader which runs
with
20ma and would like to use it to archive all my pdp-11
(and some pdp-8) paper tapes. But I need a converter...
Can anyone help? Any pointers to a simple schematic?
As a quick and dirty alternative:
The original IBM asynch adapter for the PC and XT was jumperable to
operate as EIA OR 20 ma! You could use a PC with one jumpered 20ma plus
one "regular" serial card as your converter.
--
Fred Cisin cisin(a)xenosoft.com
XenoSoft http://www.xenosoft.com
PO Box 1236 (510) 558-9366
Berkeley, CA 94701-1236