On 2020-06-18 6:06 a.m., Peter Coghlan via cctalk wrote:
To get somewhere near back on topic, I am trying to set up a synchronous
serial link between two MicroVAX 3100 machines with DSH32 (or DST32 maybe)
interfaces. One of the options I have is a BC19D cable and a BC19V cable
which seem to be identical or nearly identical. Each plugs into a DSH32
at one end and has a V.24 DB25 connector at the other end. I don't seem
to have anything available in the way of a pair of suitably similar modems
or a modem eliminator to put between the two V.24 connectors. Can anyone
suggest some kind of a quick hardware hack that I could use to fill the
gap? Is a pair of DB25 sockets with crossed over wiring betweeen them
sufficient or do I need something that generates clock signals too?
Regards,
Peter Coghlan.
While I have no experience with MicroVAX, I do recall that on the
machine I was involved with synchronous communications on, IBM terminals
and systems, there was an option for the interface to provide clocking
and I suppose it might be possible to set one side to provide the
transmit and receive clocks and cross them over to the other interface,
but I have never tried that. When I worked in a development center with
a room full of S/38 and S/36 we had a modem rack with a large number of
Gandalf modem eliminators that provided clocking to the interface.
In the field the most common setup was to have the modem provide the
clocks as the common carrier could synchronize them over a long distance.
Paul.
