Rockwell Automation 1775-S5_SR5,D17756.5.5 User Manual PLC-3 FAMILY I/0 - Manual (Page 92)

Chapter
6
6-1
Programming DH and DH+ Message
Procedures
This chapter explains how to create, edit, and use the message instruction
to operate the DH and DH+ communication channel on the scanner. This
chapter helps you learn how to:
enter a message instruction into the ladder program
program message command, functions, and procedures
add comments to a message procedure
program message procedures to monitor and recover from errors that
occur during message command execution
You do not always have to create a message procedure. If you want to
execute just a single assignment command that is not longer than 120
characters, you can enter that command in the message-instruction block
(Table 6.A). If you want to execute more than one assignment command,
you must create a message procedure to contain those commands.
The execution of a single assignment command takes place once the
scanner receives the message instruction from the CPU. However, when a
message instruction contains a message procedure, the scanner must first
store the symbols within your procedure into system memory and begin
retrieving the procedure lines from system memory. Allow for this
initialization time when initiating procedures. After this initial time, the
commands within a procedure execute as fast as single commands within a
message instruction.
Chapter Objectives
Message Instruction
Considerations