Mitsubishi Electric MELSEC iQ-R Series Programming Manual page 712

Processing details
• These instructions compare the single-precision real number data specified by (s1) with the single-precision real number
data specified by (s2), and according to the result (small, equal, or large), (d), (d)+1, or (d)+2 is turned on.
X0
ECMP
(d)
Turns on when [(s1), (s1)+1] > [(s2), (s2)+1]
(d)+1
Turns on when [(s1), (s1)+1] = [(s2), (s2)+1]
(d)+2
Turns on when [(s1), (s1)+1] < [(s2), (s2)+1]
Operation error
Error code Description
(SD0)
The value input to (s1) and (s2) is -0, a subnormal number, NaN (not a number), or .
3402H
7 APPLICATION INSTRUCTIONS
710
7.9 Real Number Instructions
(s1) (s2) (d)