Rockwell Automation 2755 Enhanced Decoder Series B - Manual (Page 323)

Connecting to a Host E–5
Publication 2755-833
The RS-422 interface uses pins 7, 14, 15, 16, 17, 18, and 19 of the
HOST port connector. The transmit data and receive data lines are:
Pin 14 TxB+ Transmits data from the decoder to the host.
Pin 15 TxA– Transmits data from the decoder to the host.
Pin 16 RxA’– Receives data from the host.
Pin 17 RxB’+ Receives data from the host.
RS-422 communication lines are unterminated. To enable network
termination (120 Ohm resistor in series with a 0.01 microfarad
capacitor), connect pins 18 and 19 together.
Important: We recommend you terminate the RS-422 lines if
excessive noise occurs on long RS-422 communication links.
RS-422 does not use modem control lines. However, the
configuration software does allow optional flow control using
XON/XOFF characters. The options are:
•
RS422. No flow control.
•
RS422 XON/XOFF. Enable XON/XOFF flow control.
The RS-422 communication interface and protocol is selected during
configuration. See the Host Communications configuration screen.
Figure E.4 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.4 Connecting NEMA Type 4 Decoder to Host using
RS-422
P
R
S
T
U
V
TxB +
TxA –
RxA’–
RxB’ +
RxB’ +
RxA’ –
TxA –
TxB +
Host RS-422 Port
*
*
*
*
* Pin designations depend
on host device.
Shield➀
➀ Ground to back shell following 2755-NC17 instructions.
RS-422
Termination
D
* SIG GND
SIG GND
Host Port
2755-NC17 Connector
on Decoder