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Troubleshooting Section 10-2
■ Reference Information
Cycle Time Too Long
■ Reference Information
Illegal Area Access Error
If the PLC Setup has been set to stop operation for an ille-
gal access error, the Access Error Flag will turn ON when
an illegal access error has occurred.
The following operations are considered illegal access:
• Reading/writing the parameter area
• Writing to an area without memory installed
• Writing to a write-protected area
• Indirect DM addressing BCD error
Refer to A298 and A299 (instruction program address when
the program fails) and take corrective actions so that illegal
area access errors will not occur. Alternatively, set the PLC
Setup so that PLC operation will not stop when an instruc-
tion error occurs.
No END Error
This error occurs when there is not an END(001) instruction
in the program within a task.
Insert an END(001) instruction at the end of the program
allocated to the task stored in A294 (task number when the
program fails).
Task Error
This error is generated by any of the following conditions.
1. There is not an executable cyclic task (active).
2. There is no specified interrupt task when an interrupt is
generated (input interrupt, high-speed counter interrupt,
scheduled interrupt, or external interrupt).
1. Check the properties of the executable cyclic task and set
at least one task to start when operation starts.
2. Create a task for the number stored in A294 (task number
when the program fails).
Differentiation Overflow Error
Differentiation instructions were repeatedly inserted or
deleted using the online editor and the system restriction
was exceeded.
Change the operating mode to PROGRAM mode and then
return to MONITOR mode.
Illegal Instruction Error
Execution of an unexecutable instruction was attempted.
For a CPU Unit with 10, 14 or 20 I/O Points, the instruction
operand will be given in D10000 to D31999.
Check the program, correct the problem, and transfer the
program to the CPU Unit again.
UM Overflow Error
An attempt was made to execute a program that exceeds
the user program capacity.
Transfer the program again using the CX-Programmer.
Error flag Program Error Flag, A401.09
Error code (A400) 80F0
Error information Program error details, A294 to A299
Probable cause Possible remedy
This error occurs when the cycle time PV exceeds the max-
imum cycle time set in the PLC Setup.
Review the program to decrease the cycle time or change
the maximum cycle time set in the PLC Setup.
Refer to the Maximum Interrupt Task Processing Time
(A440) and study the maximum cycle time.
The cycle time can be decreased using the following meth-
ods.
• Separate instructions not being executed into different
tasks.
• Consider using jump instructions for areas in the task that
are not executed.
• Prohibit cycle refreshing with Special I/O Units that do not
require exchange of cycle data.
Error flag Cycle Time Too Long Error, A401.08
Error code (A400) 809F
Error information ---
Probable cause Possible remedy
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