Task Flags - Omron SYSMAC CS1D-PD Series Operation Manual

Task Flags

IOM Hold Bit Operation
Forcing Bit Status
Precautions
Sharing Data Registers

8-19 Task Flags

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2. The PLC's power supply is cycled and the IOM Hold Bit is OFF or not pro-
tected in the PLC Setup.
By default, data registers are cleared when power is interrupted or the CPU
Unit is restarted.
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, and if the Data Registers
are not set to be shared between tasks (default setting), Data Registers will
be held in the following way when power is interrupted. For tasks that were
completed before power was interrupted, the values for the cycle during which
power was interrupted will be held. For tasks that were not completed before
power was interrupted, the values for the cycle before the cycle during which
power was interrupted will be held. For example, in a program with three
tasks, tasks 0, 1, and 2, if power is interrupted in the nth cycle during execu-
tion of task 1, then the execution result for the nth cycle of task 0 and the exe-
cution results for the (n−1)th cycle of tasks 1 and 2 will be held.
If the IOM Hold Bit (A50012) is ON, the PLC Setup's "IOM Hold Bit Status at
Startup" setting is set to protect the IOM Hold Bit, and the Data Registers are
set to be shared between tasks, Data Registers will not be held when the
PLC's power supply is reset (ON →OFF →ON). The Data Registers may take
undefined values. Be sure to set the values before continuing.
Bits in Data Registers cannot be force-set and force-reset.
Data Registers are normally local to each task. For example, DR0 used in
task 1 is different from DR0 used in task 2. 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 following setting can be made from the PLC properties dialog box on the
CX-Programmer to control sharing index and data registers between tasks.
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 (including extra cyclic tasks).
Section 8-19