FB_WriteRealOnDelta

FB_WriteRealOnDelta 1:

The function block enables event-driven writing of a variable of type REAL.

The FB_WriteRealOnDelta function block checks cyclically whether the value at the fSignal input has changed. The cycle time for checking is determined by the parameter tCycleTime. If 0 s is given for tCycleTime, the input signal is examined during every PLC cycle. If the comparison establishes that the current value is greater than the value fUpperLimit or lower than the value fLowerLimit, then the value of the signal is sent to the ADS device that is to be specified. The receiver is addressed by means of the AMS-NetId and the port number (see also ADS Device Identification). The position within the receiver is specified by the index group/index offset or by the symbol name. Usually this is the input image or the flags area.

The internal representation of floating point numbers differs according to the hardware being used. While Intel uses the "little endian" format, Motorola uses the "big endian" format. The input variable bSwapLowHighWord can be used to make the necessary adjustment in order to be able to exchange floating point numbers. This is necessary if floating point numbers are to be exchanged between the TwinCAT PLC on a PC and a BC9000, for example.

If the bEnable input is set to FALSE, no further signal transmission is carried out.

VAR_INPUT

VAR_INPUT
    bEnable          :  BOOL := FALSE;
    sNetId           :  T_AmsNetId;
    nPort            :  T_AmsPort;
    nIdxGrp          :  UDINT;
    nIdxOffs         :  UDINT;
    sVarName         :  STRING;
    fSignal          :  REAL;
    fLowerLimit      :  REAL;
    fUpperLimit      :  REAL;
    tCycleTime       :  TIME := t#0s;
    bSendNow         :  BOOL;
    bSwapLowHighWord :  BOOL := FALSE;
END_VAR

bEnable: Enable function block.

sNetId: AMS NetID of the ADS device to which the value is to be transmitted. (Type T_AmsNetId)

nPort: AMS port number of the ADS device to which the value is to be transmitted. (T_AmsPort)

nIdxGrp: Index group within the ADS device into which the value is to be transmitted.

nIdxOffs: Index offset within the ADS device into which the value is to be transmitted.

sVarName: Symbol name within the ADS device into which the value is to be transmitted.

fSignal: Variable whose value is to be transmitted.

fLowerLimit: Lower limit value.

fUpperLimit: Upper limit value.

tCycleTime: Cycle time in which the input signal is examined to see whether it has exceeded the limit values.

bSendNow: The value is transmitted immediately in response to a positive edge.

bSwapLowHighWord: The least significant WORD and the most significant WORD are swapped.

VAR_OUTPUT

VAR_OUTPUT
    bBusy            :  BOOL := FALSE;
    fLastSignal      :  REAL;
    bError           :  BOOL := FALSE;
    nErrorId         :  UDINT := 0;
    nErrorCnt        :  UDINT := 0;
END_VAR

bBusy: The transmission is active.

fLastSignal: Most recently transmitted value.

bError: An error occurred during the transmission.

nErrorId: Error number if an error has occurred.

nErrorCnt: Number of transmission attempts that have returned faults.

Requirements

Development environment	required TC3 PLC library
TwinCAT v3.0.0	Tc2_DataExchange