FB_MBWriteSingleReg (Modbus function 6)

This function is used to write to a single output register. 16 bit access is used.

Inputs

VAR_INPUT
    sIPAddr       : STRING(15);
    nTCPPort      : UINT:= MODBUS_TCP_PORT;
    nUnitID       : BYTE:=16#FF;
    nMBAddr       : WORD;
    nValue        : WORD;
    bExecute      : BOOL;
    tTimeout      : TIME;
END_VAR

Name	Type	Description
sIPAddr	STRING (15)	Is a string containing the IP address of the target device.
nTCPPort	UINT	Port number of the target device.
nUnitID	BYTE	Identification number of a serial sub-network device. If a device is addressed directly via TCP/IP, this value must be 16#FF.
nMBAddr	WORD	Address of the output register (word offset).
nValue	WORD	Value to be written to the register (data word).
bExecute	BOOL	The function block is enabled by a rising edge at this input.
tTimeout	TIME	States the length of the timeout that may not be exceeded by execution of the ADS command.

Outputs

VAR_OUTPUT
    bBUSY      : BOOL;
    bError     : BOOL;
    nErrId     : UDINT;
END_VAR

Name	Type	Description
bBusy	BOOL	When the function block is enabled, this output is set and remains set until a feedback is received.
bError	BOOL	If an ADS error should occur during the transfer of the command, then this output is set once the bBusy output is reset.
nErrId	UDINT	Returns the ADS error number when the bError output is set.

Sample of calling the function block in FBD

PROGRAM Test
VAR
    fbWriteSingleReg   : FB_MBWriteSingleReg;
    bWriteReg          : BOOL;
    bWriteRegBusy      : BOOL;
    bWriteRegError     : BOOL;
    nWriteRegErrorId   : UDINT;
    nMBAddr            : WORD := 4;
    nValue             : WORD := 16#1234; 
END_VAR

FB_MBWriteSingleReg (Modbus function 6) 4:

After a rising edge of "bExecute" and successful execution of the WriteSingleReg command, the value 16#1234 is written into register 5.

Requirements

Development environment	Target system type	PLC libraries to be linked
TwinCAT v3.0.0	PC or CX (x86)	Tc2_ModbusSrv