7 APPLICATION INSTRUCTIONS
7.10 Debugging and Failure Diagnosis Instructions
521
7
■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)
• The contact instruction prior to the CHK instruction does not control the execution of the CHK instruction, but rather sets the
check conditions.
• A ladder such as the one shown below can be created to perform a cycle time over check for the system shown above:
• The following points should be taken into consideration when creating a ladder for use with the CHK instruction:
*1 Output (Y) is treated as an internal relay, and cannot be output to an external device.
• 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)
*1
are as follows:
When advance operation is in progress: turn ON
When retract operation is in progress: turn OFF
At the detection of failure of
Contact No.: 62, Coil No.: 3
Before the detection of failure After the detection of failure
SM80
SD80
OFF
0
000
SM80
SD80
ON
0
623
Advance operation
M
Retract operation
(Y50)
(Y51)
Advance command (X4)
Retract command (X5)
Advance end sensor (X0)
turns ON at the detection
Retract end sensor (X1)
turns ON at the detection
Retract
Advance
Y
050
Y000
Y000
X004
CHK
X005X000
Y051
X001
Y050
X000
CHKST
T0
Y050
X000
T0
Y051
Y051
X005X004
X001
SET
RST
K100
When T0 is OFF, program jumps to the instruction
next to the CHK instruction.
Executes CHK instruction when T0 is ON.
Advances conveyor 1.
Retracts conveyor 1.
Turns ON the internal relay used for failure d
etection.
Turns OFF the internal relay used for failure detection.
check timer
Cycle time
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