19 Jun
2020
19 Jun
'20
10:43 a.m.
On Jun 19, 2020, at 10:43 AM, Ethan Dicks via cctalk
<cctalk at classiccmp.org> wrote:
On Fri, Jun 19, 2020 at 4:26 AM Dave Wade via cctalk
<cctalk at classiccmp.org> wrote:
I had the same reaction. The sync serial devices I know use modem-supplied clocks.
That's why there is such a device as a "modem eliminator", which is
different from the familiar asynchronous "null modem". A modem eliminator is
essentially a null modem plus a clock source along the lines discussed a day or two ago.
If you had a sync device that had the ability to send a local clock out, you could make a
sync null modem that would just be wires, as an async null modem is. Perhaps this is
something RS232 standardized but that wasn't adopted in the real world.
paul
Its been ages since I did this but looking here
https://www.aggsoft.com/rs232-pinout-cable/RS232.htm
I see we have a transmit clock output on pin 24, transmit clock input on 15 and RX clock
input on 17.
So if on checking with a scope I have clocks on 24, I would try linking 24 and 15 on one
side to 17 on the other side.
If you have only one clock running then that goes to 15 and 17 on both ends....
None of the devices I worked with in the 80s and 90s had clock
available on pin 24. I'm not saying none exist, but they weren't
around in the era I was doing this.