ReceiveByte

The function block ReceiveByte receives a single character from the interface corresponding to the input variable RxBuffer.

Inputs/outputs

VAR_IN_OUT
  RXBuffer         : ComBuffer;
END_VAR

Name	Type	Description
RxBuffer	ComBuffer	Receive data buffer corresponding to the interface in use.

Outputs

VAR_OUTPUT
  ByteReceived       : BOOL;
  ReceivedByte       : BYTE;
  Error              : ComError_t;
END_VAR

Name	Type	Description
ByteReceived	BOOL	If ByteReceived=TRUE after the call, then the data byte received is available in the output variable ReceivedByte. Otherwise no data has been received.
ReceivedByte	BYTE	If ByteReceived=TRUE after the call, then the data byte received is available in the output variable ReceivedByte. Otherwise no data has been received.
Error	ComError_t	If a fault occurs, Error will contain an error code.

Sample

Whenever a the function block ReceiveByte is processed in a PLC task that is running slower than the communication with the hardware, it must be observed that more than one character can be made available in each PLC cycle. The characters received should therefore be read out within a loop:

REPEAT
    Receive(RXbuffer:=RXbuffer);
    IF Receive.ByteReceived THEN
        (* Zeichen auswerten *)
    END_IF
UNTIL NOT Receive.ByteReceived
END_REPEAT

The number of passes through the loop is inevitably limited by the size of the receive data buffer (presently 300 bytes), so that an infinite loop need not be feared.

Requirements

Development environment	Target platform	PLC libraries to include
TwinCAT v3.1.4012	PC or CX (ARM, x86, x64)	Tc2_SerialCom