Publication 1762-RM001C-EN-P
Communications Instructions 21-3
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.
EN
DN
ER
MSG
Read/Write Message
MSG File MG9:0
Setup Screen
MSG
Table 21.1 Execution Time for the MSG Instruction
Controller Rung Condition When Rung Is:
True False
MicroLogix 1200 Steady State True 20.0
µ
s6.0
µ
s
False-to-True Transition for Reads 230.0
µ
s
False-to-True Transition for Writes 264
µ
s + 1.6
µ
s per word
MicroLogix 1500 Steady State True 17.0
µ
s6.0
µ
s
False-to-True Transition for Reads 198.0
µ
s
False-to-True Transition for Writes 226
µ
s + 1.4
µ
s per word
NOTE
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.
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