5 I/O Memory
5-22
CP2E CPU Unit Software User’s Manual(W614)
z Range of Values
The contents of Data Registers are treated as signed binary data and thus have a range of –32,768
to 32,767.
The content of Data Registers cannot be accessed (read or written) from the CX-Programmer.
z Data Register Initialization
The Data Registers will be cleared in the following cases:
• The operating mode is changed from PROGRAM mode to RUN/MONITOR mode or vice-versa
and the IOM Hold Bit is OFF.
• The PLC’s power supply is cycled and the IOM Hold Bit is OFF or not set to be held in the PLC
Setup.
• A fatal error occurs (except for one created with FALS).
Note If the IOM Hold Bit (A500.12) is ON, the Data Registers will not be cleared when a FALS error
occurs or the operating mode is changed from PROGRAM mode to RUN/MONITOR mode or
vice-versa.
Precautions for Correct UsePrecautions for Correct Use
• Do not use Data Registers until a value has been set in the register. The register'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.
Hexadecimal content Decimal equivalent
8000 to FFFF –32,768 to –1
0000 to 7FFF 0 to 32,767
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