Aviom 6416Y2 - Manual (Page 75)

65 s
PecIfIcatIons
RS-232/422 Pinout
The following table shows the pinout of the RS‑232/422 jack on the 6416Y2. Note that in the pinout table, some
transmit/receive functions (abbreviated as Tx/Rx) are different for RS‑232 versus RS‑422.
Pin Function
1 No Connect
2 –Rx (RS‑232), –Tx (RS‑422)
3 –Tx (RS‑232), –Rx (RS‑422)
4 +Rx (RS‑422)
5 Ground
6 +Tx (RS‑422)
7 No Connect
8 No Connect
9 Ground
DB9 cables are available with male‑to‑male, female‑to‑female, and male‑to‑female connectors. Aviom’s RS‑
232/422 port uses a male DB9 connector and therefore requires a cable with a female connector. The format of
the connector at the other end of the cable (male/female) is dependent upon the equipment being connected to.
However, connection to other equipment will usually require a female‑to‑female cable.
There are many different types of DB9 cables available, but Aviom selected a pinout for our DB9 connector that
would allow both RS‑232 and RS‑422 connections to be made with off‑the‑shelf cables. A “null modem” cable
should be used in RS‑232 mode. Unfortunately, there are several different types of cables referred to as null
modem cables. A true null modem cable crosses pins 2 & 3, 4 & 6, and 7 & 8. Pin 5 will be connected straight
through, but pins 1 and 9 will not (though pin 1 will be connected to pin 6 at each end). An example of this type
of cable is the L‑Com CSNULL9FF‑XA (where X = cable length).
An example of the type of null modem cable that should be avoided is the L‑Com CSNULL9FF‑X (where X = cable
length). This is a straight‑through cable 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, the 6416Y2 requires that a straight‑through cable be used
between the Aviom and Yamaha RS‑422 ports. An example of this type of cable is the L‑Com CRMN9FF‑X (where
X = cable length).
If a problem is encountered with the 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 RS‑232 operation. 2.
P N
ote
The Aviom RS‑232 port does not support the CD, DTR, DSR, RTS, CTS, or RI signals.