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MELSEC-Q
8 MULTITASK PROCESSING
8.2 How to Synchronize the Execution (Event Control)
In the multitask processing, the processing of each program proceeds independently.
Therefore, correct data may not be received, depending on the timing, when the data
needs to be exchanged between programs.
Event control is a method for synchronizing the executions. A program is kept waiting
for a signal (WAIT status), and is allowed to continue its execution when the
appropriate signal (event) is given.
B
B
B
A
A
A
Task A
Task B
(Signal)
You may
start.
In addition to the BASIC programs, a predefined extension relay (EM) in the
communication module can also generate signals for releasing the wait status.
It is possible to perform event control that synchronizes the executions of the BASIC
programs in AD51H-BASIC. In order to achieve this, define events according to the
specific procedures and specify the settings so that event generation is enabled.
