Mitsubishi Electric MELSEC-Q00U(J)CPU User Manual page 546

(2)
Method of avoiding "OPERATION ERROR" (error code: 4140) in the floating-point data
comparison instructions
As shown in the modification examples below, connect the contacts of valid data flag in series for each floating-
point data comparison instruction. (Use AND connection for connecting the contact of the valid data flag and the
floating-point data comparison instruction.)
Ensure that there is no line (OR connection) between the valid data flag and the floating-point data comparison
instruction.
<Modification example 1>
(Before modification)
Valid
data
flag
<Modification example 2>
(Before modification)
Valid
data
flag
M200
544
E<= D100 E10
D100 E200
E>=
E<= D100 E10
M201
(After modification)
E<= D100
Valid
data
flag
D100
E>=
Valid
data
flag
Make sure that there is no line (OR connection)
between the signal which shows the
floating-point data validity (valid data flag) and
the floating-point data comparison instruction.
(After modification)
E<= D100
Valid
data
flag
M200 M201
Valid
data
flag
E10
E200
E10