6
ESP-4 MI Serial Hub Installer/User Guide
Adaptors
Two adaptors are available from Avocent to enable use of standard CAT 5 cable twisted pairs for
RS-422 receive and transmit signals, plus one of the pairs for the RS-485 signal pair.
Table 2.4 lists the pin assignments for the RS-422 CAT 5 adaptor.
4
TxD (-)
Transmit Data (neg)
Output
5
GND
Ground
N/A
6
DSR (RS-232)
Data Set Ready (remains RS-232)
Input
7
RTS * (RS-232)
Request to Send (remains RS-232) *
Output
8
CTS * (RS-232)
Clear to Send (remains RS-232) *
Input
9
N/C
N/A
N/A
* 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.
Table 2.3: RS-422 and RS-485 Serial Port Pin Assignments (Continued)
Pin Number
RS-422/485 *
Description
Direction
Table 2.4: RS-422 CAT 5 Adaptor Pin Assignments
Pin Number - DB-9
RS-422
Description
Pin Number - RJ-45
1
RxD (+)
Receive Data (pos)
1
2
RxD (-)
Receive Data (neg)
2
3
TxD (+)
Transmit Data (pos)
4
4
TxD (-)
Transmit Data (neg)
5
5
GND
Ground
N/C
6
DSR (RS-232)
Data Set Ready
N/C
7
RTS (RS-232)
Request to Send
N/C
8
CTS (RS-232)
Clear to Send
N/C
9
N/C
N/A
N/C