Rockwell Automation 2755 Enhanced Decoder Series B - Manual (Page 321)

Connecting to a Host E–3
Publication 2755-833
Pin # Modem
Control Line
Function Descriptions
20 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.
4 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.
4 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.
5 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.2 shows how to connect the NEMA Type 4 decoder to a
host using RS-232. Use a Belden 8303 cable, Alpha 45123 cable, or
equivalent.
Figure E.2 Connecting NEMA Type 4 Decoder to a Host
Computer using RS-232
SIG GND➁
RTS
C
B
F
J
D
E
TD➁
RD➁
CTS
DTR
RD
TD
CTS
RTS
SIG GND
DSR
Host Port
2755-NC17 Connector
on Decoder
Host RS-232 Port
*
*
*
*
*
*
* Pin designations depend
on host device.
Shield➀
➀ Ground to back shell following 2755-NC17 instructions.
➁ Pins C, B, and D are the minimum connections.
All unused pins should be left open.
H DSR DTR *
Pins F, J, and E are optional flow control lines. Flow control options
are:
•
RS-232
No flow control.
•
RS-232 XON/XOFF
The XOFF character from the host suspends transmission and the
XON character resumes transmission. The receiving device
removes the XON/XOFF characters from the message.
•
RS-232 RTS/CTS-1
Enables the RS-232 (RTS and CTS) control lines for flow control.