Paul Berger wrote:
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.
Thanks for your reply Paul. My eventual goal is to be able to use the
synchronous serial interface on a MicroVAX to connect to IBM machines that
only support bisync lines. However, I don't have access to any such IBM kit
at the moment so I have to make do with trying to get the MicroVAX to talk
to another instance of itself for now.
As I mentioned in another reply, I have a pair of baseband synchronous modems
and were it not for a speed incompatibility between them and the MicroVAX
synchronous serial interfaces I have access to, plus another probably minor
snag, it looks very much like they would do the job when suitably jumpered.
There is even a card in the bottom of each modem case giving details of
all the jumper settings!
Regards,
Peter.
Paul.
