Preface
24 Rockwell Automation Publication MOTION-RM002H-EN-P-February 2018
If the controller: Then:
Does not detect an error when the instruction
executes
The controller sets the .DN bit.
Detects an error when the instruction executes
The controller sets the .ER bit and stores an error
code in the control structure.
3. The next time the rung becomes false after either the .DN or .ER bit sets,
the controller clears the .EN bit.
4. The controller can execute the instruction again when the rung becomes
true.
Message type motion instructions send one or more messages to the servo module.
Examples of message type instructions include the:
• Motion Direct Drive On (MDO) instruction
• Motion Redefine Position (MRP) instruction
Message type instruction work as follows:
1. When the rung that contains the motion instruction becomes true, the
controller:
• Sets the enable (EN) bit.
• Clears the done (DN) bit.
• Clears the error (ER) bit.
2. The controller begins to execute the instruction by setting up a message
request to the servo module.
Tip:
The remainder of the instruction executes in parallel to the program scan.
3. The controller checks if the servo module is ready to receive a new message.
4. The controller places the results of the check in the message status word of
the control structure.
5. When the module is ready, the controller constructs and transmits the
message to the module.
Tip:
This process may repeat several times if the instruction requires multiple
messages.
6. The instruction executes.
Instructions
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