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
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PeCifiCations
