Allen-Bradley Series B

Chapter 3
Host Computers and Display Terminals
3–4
The Host Computer port is configured as a Data Terminal Equipment (DTE)
device. Table 3.A defines which pins of the 25 pin (female) D-shell
connector are used to provide RS-232-C and RS-422 communications.
Pin Function Abb. What This Pin Does
1 Protective Ground GND Electrically bonded to the chassis and to the metal shell of the 25-pin connector. When plastic shell
(non-shielded) connectors are used on the communications cable, the cable shield drain wire should
be connected to this pin.
2 RS-232-C Transmitted
Data (Output)
TxD Serial output from the decoder.
3 RS-232-C Received
Data (Input)
RxD Serial input data from the host computer. Escape sequence commands for programming and control
are sent to this pin.
4 RS-232-C
Request To Send
RTS Indicates to the host computer that the decoder is on-line. When RTS/CTS handshaking is enabled,
RTS will go high when the terminal or decoder wishes to transmit.
5 RS-232-C
Clear To Send
CTS The CTS input must be driven greater than +3 VDC or left unconnected to allow the decoder to
output decoded label information. When CTS is less than -3 VDC, transmission from the decoder
will cease within 1-character transmission time.
When the host is receiving input from the local display terminal, CTS is driven low.
6 RS-232-C
Data Set Ready
DSR Internally connected to Pin 20 to provide loopback of DTR signal.
7 Signal Common COM This is the signal reference common which must be connected to signal common on the host
computer. Pins 1, 7, and 25 are tied together in the decoder and tied to chassis ground.
14 RS-422 Transmitted
Data (output)
TxB+ This RS-422 line is used to send data from the decoder to the host.
15 RS-422 Transmitted
Data (output)
TxA- This RS-422 line is used to send data from the decoder to the host.
16 RS-422
Receive Data (input)
RxA’- This RS-422 line is used to receive data from the host.
17 RS-422
Receive Data (input)
RxB’+ This RS-422 line is used to receive data from the host.
20 RS-232-C
Data Terminal Ready
DTR Internally connected to pin 6 to provide loopback of DSR Signal.
25 Signal Common COM See comments for Pin 7.
Note: When RTS/CTS Handshaking is enabled, both the Host and Display
Terminal ports must either support the RTS/CTS Handshaking protocol, or
the Display Terminal port’s RTS/CTS lines must be unconnected.
Host Computer Port Pinout