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Task Flags Section 9-19
2. The PLC’s power supply is cycled and the IOM Hold Bit is OFF or not pro-
tected in the PLC Setup.
IOM Hold Bit Operation If the IOM Hold BIt (A50012) is ON, the Data Registers won’t be cleared when
a FALS error occurs or the operating mode is changed from PROGRAM mode
to RUN/MONITOR mode or vice-versa.
If the IOM Hold BIt (A50012) is ON and the PLC Setup’s “IOM Hold Bit Status
at Startup” setting is set to protect the IOM Hold Bit, the Data Registers won’t
be cleared when the PLC’s power supply is reset (ON
→OFF →ON).
Precautions Data Registers are normally local to each task. For example, DR0 used in
task 1 is different from DR0 used in task 2. (With CJ1-H CPU Units, a PLC
Setup setting can be made from the CX-Programmer to share Data Registers
between tasks.)
The content of Data Registers cannot be accessed (read or written) from a
Programming Device.
Do not use Data Registers until a value has been set in the register. The reg-
ister’s operation will be unreliable if they are used without setting their values.
The values in Data Registers are unpredictable at the start of an interrupt
task. When a Data Register will be used in an interrupt task, always set a
value in the Data Register before using the register in that task.
Sharing Data Registers The following setting can be made from the PLC properties dialog box on the
CX-Programmer to control sharing index and data registers between tasks.
Note This function is not supported by CJ1-CPU@@ CPU Units.
9-19 Task Flags
Task Flags range from TK00 to TK31 and correspond to cyclic tasks 0 to 31. A
Task Flag will be ON when the corresponding cyclic task is in executable
(RUN) status and OFF when the cyclic task hasn’t been executed (INI) or is in
standby (WAIT) status.
Note These flags indicate the status of cyclic tasks only, they do not reflect the sta-
tus of interrupt tasks.
Task Flag Initialization The Task Flags will be cleared in the following cases, regardless of the status
of the IOM Hold Bit.
1,2,3... 1. The operating mode is changed from PROGRAM mode to RUN/MONITOR
mode or vice-versa.
2. The PLC’s power supply is cycled.
Forcing Bit Status The Task Flags cannot be force-set and force-reset.
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