Publication 1766-RM001A-EN-P - October 2008
398 Communications Instructions
The example rung shows a conditional SVC, which is processed only
when an outgoing message is in the communications queue.
MSG - Message
Instruction Type: output
Any preceding logic on the message rung must be solved true before the
message instruction can be processed. The example below shows a
message instruction.
If B3:0 is on (1), the MSG rung is true, and MG11:0 is not already
processing a message; then MG11:0 is processed. If one of the four
buffers is available, the message and its associated data are processed
immediately.
TIP
You may program the SVC instruction unconditionally across the rungs.
This is the normal programming technique for the SVC instruction.
EN
DN
ER
MSG
Read/Write Message
MSG File MG9:0
Setup Screen
MSG
Execution Time for the MSG Instruction
Controller Rung Condition When Rung Is:
True False
MicroLogix
1400
Steady State True 2.5670 µs 0.7310 µs
False-to-True Transition for Reads 48.1677 µs 0.8510 µs
False-to-True Transition for Writes 58.8510 µs 0.9177 µs
TIP
How quickly the message is actually sent to the destination device
depends on a number of issues, including the selected channel’s
communication protocol, the baud rate of the communications port, the
number of retries needed (if any), and the destination device's readiness to
receive the message.
EN
DN
ER
0000
B3:0
0
MSG
Read/Write Message
MSG File MG11:0
Setup Screen
0
B3:0
efesotomasyon.com - Allen Bradley,Rockwell,plc,servo,drive
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