Rockwell Automation 2755-DM9, -DM9E High Speed Decoder - Manual (Page 93)

A–B
7 Chapter
7–1
Host Commands Using the RS or RS-422
Interface
In this chapter, we tell you how to send host commands to the decoder when
you are using either the RS-422 or RS-232 communications interface. Along
with each command, we also provide the format of the decoder’s response.
The commands that a host device sends to the decoder using the RS-232 or
RS-422 interface consist of ASCII character strings. In response to a
command, the decoder will transmit a response code (also an ASCII
character string). There are two basic types of host commands:
•
Single character commands
•
Two character commands
The RS-485 communications interface has an application layer which can
use the ASCII command protocol. Refer to Appendix E for a protocol
selection chart which lists all of the protocol options.
Single Character Commands
There are four single character commands:
•
Start Scan Character
•
Stop Scan Character
•
ACK Character
•
NAK Character
The characters that are used for the single character commands are selected
by you as part of the configuration of the decoder. Refer to the description of
the setup screen #1 in Chapter 4.
If you specified the decode trigger to be a host command, single character
commands are used to stop and start the scan:
START SCAN COMMAND - When the decoder receives the start scan
command, it will begin scanning. The decoder will continue to scan until
one of the ending conditions occurs.
STOP SCAN COMMAND - The stop scan command informs the decoder to
stop scanning.
Chapter Objectives
RS-232/RS-422 ASCII Command
Protocol