DRAND

DRAND 1:

Instances of function blocks are created according to IEC61131-3, and then called, or otherwise accessed, from with the PLC program using the instance names. The function block DRAND permits generation of a (pseudo-) random number of type REAL.

VAR_INPUT

VAR_INPUT
    Seed    : INT;
END_VAR

Seed: initial value to define the random number sequence.

VAR_OUTPUT

VAR_OUTPUT
    Num     : REAL;
END_VAR

Num: this output returns a pseudo-random number in the range 0.0 ... 1.0 with single precision. The generator here creates a number series with 1075 stochastic values per period.

Sample of calling the function block in FBD:

DRAND 2:

In the sample the REAL value 0.643412 is generated and returned. The input parameter ”Seed" affects the initial value of the series. If, for instance, a deterministically reproducible random number series is desired in different sessions, and identical ”Seed" value must be used.

Requirements

Development environment	Target platform	PLC libraries to include
TwinCAT v2.7.0 and above	BCxxxx (165)	Standard.Lb6, PlcSystemBC.Lb6, TcPlcUtilitiesBC.Lb6