F_SwapReal

The way in which a REAL number is represented in the memory of a bus controller (165) is different from the way a REAL number is represented in the memory of an Intel system (PC). In order to represent a bus controller's REAL number correctly in a PC, it is necessary for the high and low words of the REAL number to be swapped. Under the programming environment this is already done in online or simulation mode.  To be able to request the REAL data of a Bus Controller via the network (ADS protocol, ADSDLL, AdsOcx etc.) and represent them properly on an Intel PC, the REAL data have to be converted into the correct format. This can either be done in the bus controller or in the PC. The function F_SwapReal can be used to convert the REAL variables (e.g. variables to be read by a VB application or recorded with TwinCAT Scope View) into a suitable format on the PC side. The fVal parameter that is passed is not affected by the conversion. The function returns a new REAL number with a modified representation in memory.

FUNCTION F_SwapReal : REAL

VAR_INPUT
    fVal    :REAL;
END_VAR

PROGRAM MAIN
VAR
    Real_165        : REAL;
    Real_i386 AT%MB0: REAL;
END_VAR

(* ADSREAD(.... ADR(Real_165), SIZEOF(Real_165)... );
...
...
...
*)
Real_i386 := F_SwapReal( Real_165 );
Real_i368 := Real_i368 + 0.001;