Rockwell Automation 2755-DM9, -DM9E High Speed Decoder - Manual (Page 86)

Chapter 6
Communicationg With a Host
6–4
Figure 6.2
Communications With RS-232 Host Device
CTS
RD
TD
HOST Port on Decoder,
Data Terminal Equipment (DTE)
Note: Connect shield to shell of HOST
port cable connector.
RD (RECEIVE DATA)
RTS (REQUEST TO SEND)
CTS (CLEAR TO SEND)
SIGNAL GROUND
1
2
3
CHASSIS GROUND
TD (TRANSMIT DATA)
Host Device: Exact pin
designations depend on specific
host device used.
4
5
7 SG
DTR (DATA TERMINAL READY)
20
Chassis
Ground
DSR
RS-232 port on Host
Note: Control signals CTS, RTS , and
DTR may or may or may not be required
depending upon decoder configuration.
Cable :
Use 3 wire Belden 9363, 9533,
6 wire 9536, or equivalent.
RTS
As shown in Figure 6.1, the RS-422 interface uses pins 14 (B), 15 (A), 16
(A’), and 17 (B’). The send data and receive data lines are:
•
B is the + Send Data (SD) line.
•
A is the - Send Data (SD) line.
•
B’ is the + Receive Data (RD) line.
•
A’ is the - Receive Data (RD) line.
The send data lines carry data from the decoder to the host device. The
receive data lines carry data from the host to the decoder.
No flow control lines are used in the RS-422 interface. Optional flow control
is provided using XON/XOFF control which is selected by the HOST
PROTOCOL configuration parameter (described in Chapter 4). There are
two options:
•
RS-422: no flow control.
•
RS-422 XON/XOFF: XON/XOFF flow control.
The RS-422 communication lines are unterminated. You can enable a
termination network (120 ohm resistor in series with a 0.01 microfarad
capacitor) by connecting pins 18 and 19 together.
RS-422 Interface