ModbusRequest (FB)¶

FUNCTION_BLOCK ModbusRequest

In addition to the predefined Modbus commands defined in the tab Modbus Slave Channel, this function block allows to execute dynamically additional commands in the application. For this programmatically created commands CODESYS does not provide an I/O mapping but input/output data ranges of type ARRAY OF BYTE or ARRAY OF WORD.

InOut:

Scope	Name	Type	Initial	Comment
Inout	slave	ModbusTCPSlave
Input	xExecute	BOOL		Rising edge: Action start Falling edge: Resets outputs If a falling edge occurs before the function block has completed its action, the outputs operate in the usual manner and are only reset if either the action is completed or aborted (xAbort), or in the event of an error. In this case, the corresponding output values (xDone, xError, iError) are present at the outputs for exactly one cycle.
	xAbort	BOOL		If this input is TRUE, the action is stopped immediately and all outputs are reset to their initial values.
	usiUnitID	USINT	16#FF	This field is used for routing purpose when addressing a MODBUS serial line sub-network. On TCP/IP, the MODBUS server is addressed using its IP address, the MODBUS Unit Identifier is useless (value 0xFF has to be used). On serial line, Modbus devcies are adressed with Uint-IDs from 1 to 247, 0 is used as broadcast address.
	ModbusCommand	ModbusCommand		The Modbus Command to be executed. Supports FCs for bit and word access
	pSendData	POINTER TO BYTE		Pointer to a buffer holding the data to be send to the Slave For Register access the buffer is of type ARRAY[0..ModbusCommand.uiWriteLen - 1] OF WORD. For Bit access the buffer is of type ARRAY[0..ModbusCommand.uiWriteLen / 8] OF BYTE
	pRecvData	POINTER TO BYTE		Pointer to a buffer for writing the data received from a Slave For Register access the buffer is of type ARRAY[0..ModbusCommand.uiReadLen - 1] OF WORD. For Bit access the buffer is of type ARRAY[0..ModbusCommand.uiReadLen / 8] OF BYTE
Output	xBusy	BOOL		Is TRUE as long as a request is in progress
	xDone	BOOL		Is TRUE if a request finished successfully
	xError	BOOL		Is TRUE if a request finished unsuccessfully
	xAborted	BOOL		Is TRUE after a request in progress has been aborted by “xAbort”
	ModbusError	MB_ErrorCodes	MB_ErrorCodes.UNDEFINED	Specifies the current error as defined in the “MB_ErrorCodes” enumeration