XFC_EL2252_V2

The function block XFC_EL2252_V2 handles the output of a digital cam with the EL2252 XFC timestamp terminal.

The output of the data to the terminal takes place only shortly before reaching the timestamp of one of the outputs. Four PLC cycles are required for activation and acknowledgement of the outputs. Only then can a further edge change take place. The minimum time between two edge changes of the output signal is therefore four PLC cycles, in order to prevent errors or loss of precision. If the output signal is generated by a cam controller, a minimum cam width can be calculated from the maximum velocity and the PLC cycle time.

The outputs Output1 and Output2 cannot be used completely independently of each other since the activation takes place with only one timestamp. As a prerequisite, the switching edges of both channels must be sufficiently far apart. In this case, the respectively nearest timestamp is applied to the block.

Inputs

VAR_INPUT
    ForceWhenLate : BOOL; 
END_VAR

Name	Type	Description
ForceWhenLate	BOOL	If ForceWhenLate is TRUE, the output is activated even if the time stamp is already exceeded. It is recommended to set ForceWhenLate to prevent the loss of a switching edge in case of fluctuations of the time signal.

/ Inputs/outputs

VAR_IN_OUT
    Output1       : OUTPUT_REF;
    Output2       : OUTPUT_REF;
    TrackOptions1 : TRACK_REF;
    TrackOptions2 : TRACK_REF;
    EL2252        : EL2252_IoInterface;
END_VAR

Name	Type	Description
Output1	OUTPUT_REF	Output state for channel 1 of the Terminal. The data structure Output contains the calculated state of the digital output and the associated time stamp for the output at a digital XFC output terminal.
Output2	OUTPUT_REF	Output state for channel 2 of the Terminal. The data structure Output contains the calculated state of the digital output and the associated time stamp for the output at a digital XFC output terminal.
TrackOptions1	TRACK_REF	The TrackOptions1 data structure contains the parameterization of Cam Track 1 for Output1.
TrackOptions2	TRACK_REF	The TrackOptions2 data structure contains the parameterization of Cam Track 2 for Output2.
EL2252	EL2252_IoInterface	Process image of the terminal

Outputs

VAR_OUTPUT
    Error             : BOOL;
    ErrorID           : UDINT;
    ErrorOutputMissed : BOOL;
    PrecisionReduced  : BOOL;
END_VAR

Name	Type	Description
Error	BOOL	Becomes TRUE if an error occurs.
ErrorID	UDINT	If an error output is set, this parameter supplies an error number
ErrorOutputMissed	BOOL	The exact switching point transferred in the Output1 or Output2 structures could not be maintained and the output state remains unchanged. If ForceWhenLate is TRUE, the initial state is always output and ErrorOutputMissed does not become TRUE.
PrecisionReduced	BOOL	The exact switching point transferred in the Output1 or Output2 structures could not be maintained, but the output status was output with a delay. PrecisionReduced should be regarded as a warning. It can only become TRUE if ForceWhenLate is TRUE.

Example for a position cam output

The function block XFC_PositionCam is hardware-independent and transfers the necessary switching information for output to the function block XFC_EL2252_V2 in the OutputRef1 data structure. The data structure is used for data transfer on both function blocks.

Output of two position cams on one output terminal

The outputs Output1 and Output2 cannot be used completely independently of each other with the EL2252 because activation occurs with only one timestamp. As a prerequisite, the switching edges of both channels must be sufficiently far apart (4 PLC cycles). As soon as the switching edges are closer together, they are output inaccurately.