441
CHKST, CHK
1
2
3
4
4
6
7
8
7.10
Debugging an
d failure
diagn
osis
instructions
7.10.1
CHKST, CHK
(b) The contact instruction prior to the CHK instruction does not control the execution of the CHK instruction, but rather
sets the check conditions.
(c) A ladder such as the one shown below can be created to perform a cycle time over check for the system shown
above:
(d) The following points should be taken into consideration when creating a ladder for use with the CHK instruction:
1) 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.
2) 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
*1:
Output (Y
) is treated as an internal relay, and cannot be output to an external device.
Ad
v
ance operation
M
Retract operation
(Y50)
(Y51)
Ad
v
ance command (X4)
Retract command (X5)
Ad
v
ance end sensor (X0)
turns ON at the detection
Retract end sensor (X1)
turns ON at the detection
Retract
Ad
v
ance
Y
050
Y
000
Y
000
X00
4
C
HK
X005 X000
Y
051
X001
Y
050
X000
C
HK
S
T
T
0
Y
050
X000
T
0
Y
051
Y
051
X005 X00
4
X001
S
ET
RS
T
K
100
When
T
0
i
s
O
FF
,
program
jumps
to
the
i
nstruct
i
on
next
to
the
C
HK i
nstruct
i
on
.
E
xecutes
C
HK i
nstruct
i
on
w
hen
T
0
i
s
O
N.
Ad
v
ances
con
v
eyor
1
.
Retracts
con
v
eyor
1
.
T
urns
O
N
the
i
nterna
l
re
l
ay
used
for
fa
il
ure
detect
i
on
.
T
urns
O
FF
the
i
nterna
l
re
l
ay
used
for
fa
il
ure
detect
i
on
.
check
t
i
mer
Cyc
l
e
t
i
me