Mitsubishi MELSEC Q Series Programming Manual page 555

(4) The CHKCIR and CHKEND instructions can be written at any step in the program desired.
It can be used in up to two locations in all program files being executed.
However, the CHKCIR and CHKEND instructions cannot be used in more than 1 location in
a single program file.
(5) The CHKCIR and CHKEND instructions cannot be used in low speed execution type
programs.
If a program file in which the CHKCIR or CHKEND instruction is described is set as a low
speed execution type program, an operation error will occur, and the High Performance
model QCPU/Process CPU/Redundant CPU operation will be suspended.
Operation Error
(1) In any of the following cases, an operation error occurs, the error flag (SM0) turns ON, and
an error code is stored into SD0.
• The CHKCIR or CHKEND instruction appears three or more times in all program files.
• The CHKCIR or CHKEND instruction appears two or more times in a single program file.
• The CHKEND instruction is not executed following the execution of the CHKCIR
instruction.
• The CHKEND instruction is executed although no CHKCIR instruction has been
executed.
• The CHKST and CHK instruction are used in a low speed execution type program.
• There are 10 or more F instances in a ladder pattern.
• A ladder pattern has 257 or more steps.
• A device has been encountered which cannot be used in a ladder pattern.
• Index modification has been conducted on a ladder pattern device.
CHKCIR,CHKEND
(Error code: 4235)
(Error code: 4235)
(Error code: 4230)
(Error code: 4230)
(Error code: 4235)
(Error code: 4235)
(Error code: 4235)
(Error code: 4235)
(Error code: 4235)
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