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Checking Programs Section 1-3
Note Output duplication is not checked between tasks, only within individual tasks.
Multi-word Operands Memory area boundaries are checked for multi-word operands for the pro-
gram check as shown in the following table.
1-3-3 Program Execution Check
Operand and instruction location checks are performed on instructions during
input and during program checks from the CX-Programmer. These are not,
however, final checks.
The following checks are performed during instruction execution.
Instruction
Processing Errors
An instruction processing error will occur if incorrect data was provided when
executing an instruction or an attempt was made to execute an instruction out-
side of a task. Here, data required at the beginning of instruction processing
was checked and as a result, the instruction was not executed, the ER Flag
(Error Flag) will be turned ON and the EQ and N Flags may be retained or
turned OFF depending upon the instruction.
Output duplication
(See note.)
Duplicate output check
•By bit
•By word
• Timer/counter instructions
• Long words (2-word and 4-word)
• Multiple allocated words
• Start/end ranges
• FAL numbers
• Instructions with multiple output operands
Tasks Check for tasks set for starting at beginning of operation
Task program allocation
Area Check
Check items The following functionality is provided by the CX-Programmer for
multi-word operands that exceed a memory area boundary.
• The program cannot be transferred to the CPU Unit.
• The program also cannot be read from the CPU Unit.
• Compiling errors are generated for the program check.
• Warnings will appear on-screen during offline programming.
• Warnings will appear on-screen during online editing in PRO-
GRAM or MONITOR mode.
Type of error Flag that turns ON for error Stop/Continue operation
1. Instruction Processing Error ER Flag
Note The Instruction Processing
Error Flag (A295.08) will
also turn ON if Stop Opera-
tion is specified when an
error occurs.
A setting in the PLC Setup can be used to spec-
ify whether to stop or continue operation for
instruction processing errors. The default is to
continue operation.
A program error will be generated and operation
will stop only if Stop Operation is specified.
2. Access Error AER Flag
Note The Access Error Flag
(A295.10) will turn ON if
Stop Operation is specified
when an error occurs.
A setting in the PLC Setup can be used to spec-
ify whether to stop or continue operation for
instruction processing errors. The default is to
continue operation.
A program error will be generated and operation
will stop only if Stop Operation is specified.
3. Illegal Instruction Error Illegal Instruction Error Flag
(A295.14)
Fatal (program error)
4. UM (User Memory) Overflow
Error
UM Overflow Error Flag (A295.15) Fatal (program error)
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