Omron CP1L-EL20DR-D, Operation Manual

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Index Registers Section 4-11
4-11-2 Precautions for Using Index Registers
Precautions Do not use a Index Register until a PLC memory address has been set in the
register. The pointer operation will be unreliable if the registers are used with-
out setting their values.
The values in Index Registers are unpredictable at the start of an interrupt
task. When an Index Register will be used in an interrupt task, always set a
PLC memory address in the Index Register with MOVR(560) or
MOVRW(561) before using the register in that task.
Each Index Register task is processed independently, so they do not affect
each other. For example, IR0 used in Task 1 and IR0 used in Task 2 are dif-
ferent. Consequently, each Index Register task has 16 Index Registers.
Limitations when Using Index Registers
• It is only possible to read the Index Register for the last task executed
within the cycle from the CX-Programmer. If using Index Registers with
the same number to perform multiple tasks, it is only possible with the
CX-Programmer to read the Index Register value for the last task per-
formed within the cycle from the multiple tasks, nor is it possible to write
the Index Register value from the CX-Programmer.
• It is not possible to either read or write to the Index Registers using Host
Link commands or FINS commands.
• A setting can be made from the CX-Programmer to share Index Registers
between tasks. This setting will be enabled uniformly for all Index Regis-
ters and Data Registers.
Sharing Index 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.
Monitoring Index Registers
It is possible to monitor Index Registers as follows:
To use the Programming Devices to monitor the final Index Register values
for each task, or to monitor the Index Register values using Host Link com-
mands or FINS commands, write a program to store Index Register values
from each task to another area (e.g., DM area) at the end of each task, and to
read Index Register values from the storage words (e.g., DM area) at the
beginning of each task. The values stored for each task in other areas (e.g.,
DM area) can then be edited using the CX-Programmer, Host Link com-
mands, or FINS commands.