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■CHK
• The CHK instruction is the instruction used for the bidirectional operation to confirm the nature of the system failure. When
the CHK instruction is executed, a failure diagnosis check is conducted with the designated check conditions, and if a
failure is detected, SM80 is turned ON, and the failure number is stored at SD80 as a BCD value.
• The error code "9010" will be returned if a failure is detected. The contact number where the failure was discovered is
stored at the upper 3 digits of SD80, and the coil number where the failure was detected is stored at the lower 1 digit of
SD80. (Point)
Before the detection of failure
SM80
OFF
SD80
0 0 0 0
• The contact instruction prior to the CHK instruction does not control the execution of the CHK instruction, but rather sets the
check conditions.
Advance end sensor (X0)
turns ON at the detection
• A ladder such as the one shown below can be created to perform a cycle time over check for the system shown above:
T0
X000
X004
X005 X000
Y050
X005 X004 X001
Y051
Y050
X000
Y051
X001
• The following points should be taken into consideration when creating a ladder for use with the CHK instruction:
• The contact numbers for the advance edge detection sensor and the retract edge detection sensor (X) must always be continuous. Further, the contact
number (X) for the advance edge detection sensor should be lower than that for the retract edge.
• Controls for the advance edge detection sensor contact number (X) and output with the identical number (Y)
When advance operation is in progress: turn ON
When retract operation is in progress: turn OFF
*1 Output (Y) is treated as an internal relay, and cannot be output to an external device.
At the detection of failure of
Contact No.: 62, Coil No.: 3
Advance
Retract
Retract end sensor (X1)
turns ON at the detection
When T0 is OFF, program jumps to the instruction
CHKST
next to the CHK instruction.
Executes CHK instruction when T0 is ON.
CHK
Y050
Advances conveyor 1.
SET
Y000
Turns ON the internal relay used for failure detection.
Y051
Retracts conveyor 1.
RST
Y000
Turns OFF the internal relay used for failure detection.
K100
T0
Cycle time
check timer
After the detection of failure
SM80
ON
SD80
0 6 2 3
Advance command (X4)
Advance operation
(Y50)
M
Retract operation
(Y51)
Retract command (X5)
*1
are as follows:
7 APPLICATION INSTRUCTIONS
7.10 Debugging and Failure Diagnosis Instructions
7
521
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