Rockwell Automation 2755 Enhanced Decoder Series B - Manual (Page 322)

Connecting to a Host E–4
Publication 2755-833
•
RS-232 RTS/CTS-2
Enables the RS-232 (RTS and CTS) control lines for flow control.
Use this mode of flow control to communicate with Catalog No.
2760-RA or -RB module.
The RS-232 interface and flow control are selected on the Host
Communications configuration screen.
Pin # Modem
Control Line
Function Descriptions
E DTR RTS/CTS-1
RTS/CTS-2 The decoder sends a DTR (Data Terminal Ready) signal to tell the host the decoder is online and capa-
ble of receiving data from the host. The DTR line remains on while the decoder is on.
F RTS RTS/CTS-1 The decoder sends the RTS (Request to Send) signal to tell the host it is ready to send data. When the
host receives an RTS signal from the decoder, the host must assert CTS to tell the decoder to begin
sending data. When the decoder stops sending an RTS, the host must stop sending a CTS before the
decoder can assert RTS again.
F RTS RTS/CTS-2 The decoder sends the RTS (Request to Send) signal to tell the host it can accept data. The host only
sends data when RTS is on.
J CTS RTS/CTS-1
RTS/CTS-2 The host sends the CTS (Clear to Send) signal to the decoder if it can accept data. The decoder only
sends data if CTS is on.
Figure E.3 shows how to connect the NEMA Type 4 decoder to a
host using RS-422. Use Belden cable 9829 (shielded, twisted pair) or
equivalent.
Figure E.3 Connecting NEMA Type 4 Decoder to Host using
RS-422
1
14
15
16
17
18
19
GND
TxB +
TxA –
RxA’–
RxB’ +
RxB’ +
RxA’ –
TxA –
TxB +
Host Port
25-pin DB Connector
on Decoder➀
Host RS-422 Port
*
*
*
*
* Pin designations depend
on host device.
Shield➁
➀ DTE = Data Terminal Equipment
➁ When nonmetallic connector shells used.
(If metal connector shell, connect shield
to shell.)
RS-422
Termination
7
* SIG GND
SIG GND
RS-422 Interface