Table 2.4: Rs-422 And Rs-485 Serial Port Pin Assignments - Avocent ESP Serial Hub Installer/User Manual

8 ESP Serial Hub Installer/User Guide
Table 2.3: RS-232 Serial Port Pin Assignments (Continued)
Pin Number
4
5
6
7
8
9
Not supported: RI, RS-422 RTS and CTS differential control signals.
Unused pins (labeled N/C) should not have wires attached to them. Floating wires could cause unbalanced
noise, shorten overall distances and degrade performance.
Table 2.4 lists the pin assignments for the RS-422 and RS-485 interfaces.

Table 2.4: RS-422 and RS-485 Serial Port Pin Assignments

Pin Number
1
2
3
4
5
6
7
8
9
* The RS-485 interface is implemented by using special cables that connect RxD(+) to TxD(+) and RxD(-) to
TxD(-), thus providing the 2-wire bidirectional interface. In addition, pins 7 and 8 should be jumpered together
to signal that the port is configured for RS-485. Pins 7 and 8 should be left open for an RS-422 configuration.
RS-232
DTR
GND
DSR
RTS
CTS
N/C
RS-422/485 *
RxD (+)
RxD (-)
TxD (+)
TxD (-)
GND
DSR (RS-232)
RTS * (RS-232)
CTS * (RS-232)
N/C
Description
Data Terminal Ready
Ground
Data Set Ready
Request to Send
Clear to Send
N/C
Description
Receive Data (pos)
Receive Data (neg)
Transmit Data (pos)
Transmit Data (neg)
Ground
Data Set Ready (remains RS-232)
Request to Send (remains RS-232) *
Clear to Send (remains RS-232) *
N/A
Direction
Output
N/A
Input
Output
Input
N/A
Direction
Input
Input
Output
Output
N/A
Input
Output
Input
N/A