Rockwell Automation 2080-LC50 Micro800 Controllers: Getting Started with CIP Client Messaging - Manual (Page 55)

Rockwell Automation Publication 2080-QS002A-EN-E - April 2013 49
Appendix
F
Programming Tips and Recommendations for
Micro800 CIP Messaging Instructions (MSG)
Programming
Recommendations for MSG
Client Instructions When programming with the Ethernet MSG instructions
(MSG_CIPSYMBOLIC, MSG_CIPGENERIC, MSG_MODBUS2), execute
the instructions as part of the normal program scan in order for the message
status to be promptly updated. Once a message is initiated it will always complete
as Success or Failure, but the instruction only updates its status when executed.
Recommended Practices
1. Do not place MSG instructions in interrupts (for example, STI) since
status bits (for example, message done status) may not be updated every
program scan.
2. Do not use MSG instructions with RETURN, TND, JUMP (LD, FBD),
IF-THEN (ST only), CASE (ST only) as status bits, (for example, message
done status) may not be updated every program scan.
For example: First MSG instruction is acceptable as it is evaluated as part
of the normal program scan. Second MSG instruction should not be used
with the Return as the message status may not be updated with correct
status if Skip_Next_Instruction becomes TRUE before the message
instruction finishes.