Rockwell-automation 2755-DM9, -DM9E High Speed Decoder Manual de usuario descargar pdf (Pagina 93)

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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

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Rockwell-automation 2755-DM9, -DM9E High Speed Decoder Manual de usuario Pagina 93