Siemens SIMATIC S7-1200

Basic instructions
8.4 Comparator operations
S7-1200 Programmable controller
252 System Manual, V4.2, 09/2016, A5E02486680-AK
8.4.3
OK (Check validity) and NOT_OK (Check invalidity)
Table 8- 33 OK (check validity) and Not OK (check invalidity) instructions
LAD
FBD
SCL
Description
Not available Tests whether an input data reference is a valid real num-
ber according to IEEE specification 754.
Not available
1
For LAD and FBD: When the LAD contact is TRUE, the contact is activated and passes power flow. When the FBD box
is TRUE, then the box output is TRUE.
Table 8- 34 Data types for the parameter
Parameter
Data type
Description
IN
Real, LReal
Input data
Table 8- 35 Operation
Instruction
The Real number test is TRUE if:
OK
The input value is a valid real number
1
NOT_OK
The input value is not a valid real number
1
1
A Real or LReal value is invalid if it is +/- INF (infinity), NaN (Not a Number), or if it is a denormalized value. A denormal-
ized value is a number very close to zero. The CPU substitutes a zero for a denormalized value in calculations.