CHK Instruction Usage Error

What does 4235 mean?

This operation error occurs when the CHK (Check) instruction is implemented improperly within the program, suspending CPU module operation. It can be caused by incorrect instruction placement between CHKST and CHK, exceeding the allowed number of CHK instructions, or attempting to use CHK/CHKST in a low-speed execution program. When this error occurs, the error flag SM0 turns ON and the error code is stored into SD0.

• Parallel ladder or NOP instruction detected within the CHK instruction scope.
• More than 150 contact instructions are used with the CHK instruction.
• CHK instruction is not executed after the CHKST instruction, or CHK is executed without a preceding CHKST.
• CHKST and CHK instructions are used in a low-speed execution type program.
• An instruction other than LD, LDI, AND, or ANI is used between the CHK instruction and the CHKST instruction.
• CHK instruction is used on three or more points across all program files being executed.
• CHK instruction is used on two or more points within a single program file.

Click steps to track your progress.

1. 1

   Verify the program ensures a CHKST instruction is placed immediately before the CHK instruction.

2. 2

   Confirm that only LD, LDI, AND, or ANI instructions exist between the CHKST and CHK instructions.

3. 3

   Ensure the total number of CHK instructions in all program files being executed does not exceed two.

4. 4

   Verify that no single program file contains more than one CHK instruction.

5. 5

   Check the program for the presence of parallel ladders or NOP instructions within the scope of the CHK instruction.

6. 6

   Review the program file's execution type; if it is a low-speed execution program, relocate or remove the CHK and CHKST instructions.