Rockwell Automation 1775-KA PLC-3 Communication Adapter Module User Manual - Manual (Page 164)

Message Formats
Appendix A
AĆ2
*Use these commands to affect only the RS–232–C port of the 1775–KA
module.
Important: In the formats shown in this section, CMD and FNC values
are expressed in hexadecimal notation. All other values are given in
decimal form. Network layer fields are shaded in blue; data link layer
fields are shaded in grey; application layer fields are not shaded.
Building a Line Monitor
This appendix presents the formats for each of the Data Highway
commands that the 1775–KA module can send and/or receive. You can
build a line monitor that allows you to see these commands as they are
sent or received by the 1775–KA module. This can be useful during
installation or when you are troubleshooting. By viewing these
commands on a line monitor, you can verify the types of messages the
1775–KA is sending or receiving and the data that is contained in the
messages.
We do not recommend building a line monitor for Data Highway
communication. Messages on the Data Highway use a different protocol.
But you can monitor communication to the RS–232–C link. To do this,
you must create a cable like the one shown in Figure A.1. This cable links
the 1775–KA module, an RS–232–C device, and a 1770–T4 Industrial
Terminal (Figure A.2). The cable you build connects the receiving data,
transmit data, and ground in the RS–232–C link to the receive data and
ground of the Industrial Terminal. A switch on the cable allows you to
choose the monitor either messages received or messages sent by the
1775–KA module.