Siemens SIMATIC S7 System Manual page 231

Selecting the data types to be compared
The data type identifier that you choose determines the required data type for the IN1 and
IN2 parameters.
Data type identifier
B
W
D
R
LAD contacts, FBD boxes STL
S7-200 SMART
System Manual, V2.3, 07/2017, A5E03822230-AF
Required IN1, IN2 data type
Unsigned byte
Signed word integer
Signed double word integer
Signed real
LDB= IN1, IN2
OB= IN1, IN2
AB= IN1, IN2
LDW= IN1, IN2
OW= IN1, IN2
AW= IN1, IN2
LDD= IN1, IN2
OD= IN1, IN2
AD= IN1, IN2
LDR= IN1, IN2
OR= IN1, IN2
AR= IN1, IN2
Comparison result
Compare two unsigned byte values:
The result is TRUE, if IN1 = IN2
Compare two signed integer values:
The result is TRUE, if IN1 = IN2
Compare two signed double integer values:
The result is TRUE, if IN1 = IN2
Compare two signed real values:
The result is TRUE, if IN1 = IN2
Program instructions
7.4 Compare
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