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(4) Replacement example of the CHKST and CHK instructions
In the example below, if the replacement program for the CHKST and CHK instructions detects a failure, a failure
number (contact number + coil number) is stored in D200 and the annunciator F200 is turned on.
(a) Example of device assignment
If the device numbers in the example above are used for other applications, assign unused device numbers
instead.
When the advance end detection sensor input performs a failure detection of Xn, assign device numbers for
the retract end detection sensor input and the failure detection output as described below.
(b) Program before replacement
TableApp.30 Example of device assignment
Before replacement After replacement
Application Device Application Device
Advance end detection sensor input 1 X100 Advance end detection sensor input 1 X100
Retract end detection sensor input 1 X101 Retract end detection sensor input 1 X101
Advance end detection sensor input 2 X102 Advance end detection sensor input 2 X102
Retract end detection sensor input 2 X103 Retract end detection sensor input 2 X103
Advance end detection sensor input 3 X104 Advance end detection sensor input 3 X104
Retract end detection sensor input 3 X105 Retract end detection sensor input 3 X105
Advance end detection sensor input 4 X106 Advance end detection sensor input 4 X106
Retract end detection sensor input 4 X107 Retract end detection sensor input 4 X107
Failure detection output 1 Y100 Failure detection output 1 Y100
Failure detection output 2 Y102 Failure detection output 2 Y102
Failure detection output 3 Y104 Failure detection output 3 Y104
Failure detection output 4 Y106 Failure detection output 4 Y106
Coil number (failure type detected) D100
Contact number D101
Failure number D200
Failure detection display F200
For index modification Z0
Advance end detection sensor input Xn
Retract end detection sensor input Xn+1
Failure detection output Yn
Figure App.11 Sample program