Aviom 6416dio - Manual (Page 86)

76 rs-232/422
with the exception of pins 2 and 3, which are crossed.
A true null modem cable is required for the interaction of the RS‑422
termination on pin 4 of the connector with the RS‑232 signals. On an RS‑232
connector, pins 3, 4, and 7 are outputs; pins 1, 2, 6, and 8 are inputs. In a
standard null modem cable, pin 4 at one end of the cable will drive pins 1
and 6 at the other end. With a 100 ohm resistor across pins 3 and 4 on the
Aviom DB9 connector, pin 3 (RS‑232 –Tx) will drive pins 1 and 6 at the other
end of the cable through the 100 ohm resistor. This isn’t a problem for most
modern RS‑232 implementations as these signals are ignored and both are
inputs.
Although there is no standard DB9 pinout for RS‑422, ours requires a
straight‑through cable to be used between Aviom and Yamaha RS‑422 ports
for control of Yamaha remote mic preamps such as the AD8HR. An example
of this type of cable is the L‑Com CRMN9FF‑X (where X = cable length).
If a problem is encountered with RS‑232 operation, there are two things that
can be done:
Try another brand of null modem cable. 1.
Cut the wire in the cable going to pin 4. It isn’t needed for 2.
RS‑232 operation.
P N
ote
: The Aviom RS‑232 port does not support the CD, DTR, DSR, RTS,
CTS, or RI signals.