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(2) Method of avoiding "OPERATION ERROR" (error code: 4101)
When the index-modified device range does not need to be checked, use the method 1).
When the index-modified device range needs to be checked, use the method 2).
1) Deselect the "Check device range at indexing" item in the PLC RAS tab of the PLC parameter dialog box so
that the index-modified device range will not be checked.
2) As shown in the modification examples below, connect the contacts of valid data flag in series for each
instruction that checks the index-modified device range.
<Modification example>
In the program before modification (on the left), the instruction immediately before the AND<> instruction is
regarded as the LD instruction. However, in the program after modification (on the right), the same instruction will
be regarded as the AND instruction.
In the program after modification, only when both contacts of M0 and M1 (or M2) turn on, the AND<> instruction
is executed. As a result, no error will be detected during index-modified device range check processing.
M0
(After modification)
(Before modification)
[Ladder mode]
[Ladder mode]
[List mode]
[List mode]
M0
M0
M1
M1
M2
M2
Valid
data
flag
LD
M0
LD
M1
AND <>
D10Z1
K5
LD
M2
AND <>
D10Z1
K10
ORB
ANB
<> D10Z1 K5
<> D10Z1 K10
<> D10Z1 K5
<> D10Z1 K10
Valid data
flag
Valid data
flag
LD
M0
AND
M1
AND <>
D10Z1
K5
LD
M0
AND
M2
AND <>
D10Z1
K10
ORB