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CHKST,CHK
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7.10 Debugging and failure diagnosis instructions
7.10.1 Special format failure checks (CHKST,CHK)
(2) Depending on the designated contact, the CHK instruction undergoes processing identical
to that shown for the ladder below:
(3) Numbers 1 to 150 from the vertical bus on the left side have been allocated as contact
numbers during failure detection.
(4) Reset SM80 and SD80 prior to forcing the execution of the CHK instruction.
After the execution of the CHK instruction, it cannot be performed once again until SM80
and SD80 have been reset.
(The contents of SM80 and SD80 will be preserved until reset by user.)
(5) A CHKST instruction must be placed before the CHK instruction.
An error will be returned if an instruction other than the LD, LDI, AND or ANI instruction is
used between the CHK instruction and the CHKST instruction. (Error code: 4235)
(6) The CHK instruction can be written at any step of the program.
However, there is a limit in the number of uses of the CHK instruction.
• Can be used up to two places in all program files being executed.
• Can be used only one place in a single program file.
An error will be returned if the CHK instruction is used exceeding the number of uses
specified above. (Error code: 4235)
SM80SET
MOV Failure No. 6 SD80
Y
X
Coil No. 6
CHK
CHKST
TO
SM80
X
X X +1 Y
X
+1
Y
SM80
SET
SET
MOV Failure No. 1 SD80
MOV Failure No. 2 SD80
SM80SET
MOV Failure No. 3 SD80
X
Y
(Detection by both advance and retraction end sensors
during advance operation of the conveyor)
(Detection by both advance and retraction end sensors
during retract operation of the conveyor)
(Advance operation of the conveyor at the detection
by the advance end sensor)
SM80
SET
MOV Failure No. 4 SD80
Y
X +1
(Retract operation of the conveyor at the detection
by the retraction end sensor)
SM80
SET
MOV Failure No. 5 SD80
Y
X +1
(Advance operation of the conveyor during no detection
by the retraction end sensor)
(Retract operation of the conveyer at the detection
by the advance end sensor)
Coil No. 1
Coil No. 2
Coil No. 3
Coil No. 4
Coil No. 5
Max. 150 contacts
Example
XX0
XX1
X
+ 1
YY0
X
Executes the same processing
as the ladder indicated above
CHK
X5 X7
X9
149 150123
Contact No.
X1A
X1C