FB_WriteByteOnDelta

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

The function block FB_WriteByteOnDelta checks cyclically whether the value at the input nSignal 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 determines that the current value is greater by the value nUpperLimit or lower by the value nLowerLimit, the value of the signal is sent to the specified ADS device. 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.

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

Inputs

VAR_INPUT
    bEnable          :  BOOL := FALSE;
    sNetId           :  T_AmsNetId;
    nPort            :  T_AmsPort;
    nIdxGrp          :  UDINT;
    nIdxOffs         :  UDINT;
    sVarName         :  STRING;
    nSignal          :  BYTE;
    nLowerLimit      :  BYTE;
    nUpperLimit      :  BYTE;
    tCycleTime       :  TIME := t#0s;
    bSendNow         :  BOOL;
END_VAR

Name	Type	Description
bEnable	BOOL	Enable function block.
sNetId	T_AmsNetID	AMS NetID of the ADS device to which the value is to be transmitted.
nPort	T_AmsNetID	AMS port number of the ADS device to which the value is to be transmitted.
nIdxGrp	UDINT	Index group within the ADS device into which the value is to be transmitted.
nIdxOffs	UDINT	Index offset within the ADS device into which the value is to be transmitted.
sVarName	STRING	Symbol name within the ADS device into which the value is to be transmitted.
nSignal	BYTE	Variable whose value is to be transmitted.
nLowerLimit	BYTE	Lower limit value.
nUpperLimit	BYTE	Upper limit value.
tCycleTime	TIME	Cycle time in which the input signal is checked to see whether it has exceeded the limit values.
bSendNow	BOOL	The value is transmitted immediately by a positive edge.

Outputs

VAR_OUTPUT
    bBusy            :  BOOL := FALSE;
    nLastSignal      :  BYTE;
    bError           :  BOOL := FALSE;
    nErrorId         :  UDINT := 0;
    nErrorCnt        :  UDINT := 0;
END_VAR

Name	Type	Description
bBusy	BOOL	The transmission is active.
nLastSignal	BYTE	Most recently transmitted value.
bError	BOOL	An error occurred during the transmission.
nErrorId	UDINT	ADS error number if an error has occurred.
nErrorCnt	UDINT	Number of failed transmission attempts.

Requirements

Development environment	required TC3 PLC library
TwinCAT v3.0.0	Tc2_DataExchange