Rockwell Automation 1775-KA PLC-3 Communication Adapter Module User Manual User Manual
Page 25
Installation
Chapter 2
2Ć13
Pinout
The necessary RS–232–C port connections are described in Table 2.D
below:
Table 2.D
RS-232-C Port Connections
Signal at the
1775-KA
Abbreviation
Pin
Input/Output
chassis/shield drain
1
transmitted data
TXD
2
Output
received data
RXD
3
Input
request to send
RTS
4
Output
clear to send
CTS
5
Input
data set ready
DSR
6
Input
transmitted data return
TXDRET
7/14
data carrier detect
DCD
8
Input
data terminal ready
DTR
20/11
Output
received data return
RXDRET
25/13
TXD (transmitted data) caries serialized data. It is output from the
RS–232 connector.
RXD (received data) is serialized data input to the RS–232 connector.
RXD and RXDRET are isolated from the rest of the circuitry on the
module.
RTS (request to send) is a request from the RS–232 connector to the
modem to prepare to transmit. It typically turns the data carrier on.
When you select the full duplex mode RTS is always asserted. When
you select the half duplex mode RTS is turned on when the module has
permission to transmit; otherwise it is off.
CTS (clear to send) is a signal from the modem to the RS–232
connector that the carrier is stable and the modem is ready to transmit.
The module will not transmit until CTS is true. If CTS is turned off
during transmission, the module will stop sending until CTS is restored.
DTR (data terminal ready) is a signal from the RS–232 connector to the
modem to connect to the phone line (that is, “pick up the phone”). The
module will assert DTR all the time except during the phone hangup