FB_MBWriteSingleReg (Modbus function 6)

VAR_INPUT

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

sIPAddr: Is a string containing the IP address of the target device.

nTCPPort: Port number of the target device.

nUnitID: Identification number of a serial sub-network device. If a device is addressed directly via TCP/IP, this value must be 16#FF.

nMBAddr: Address of the output register (word offset).

nValue: Value to be written into the register (word value).

bExecute: The function block is activated by a rising edge at this input.

tTimeout: States the length of the timeout that may not be exceeded by execution of the ADS command.

VAR_OUTPUT

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

bBusy : When the function block is activated this output is set. It remains set until an acknowledgement is received.

bError : If an ADS error should occur during the transfer of the command, then this output is set once the bBusy output is reset.

nErrId : Supplies the ADS error number when the bError output is set.

Example of calling the 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

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

Requirements