FB_MBWriteCoils (Modbus function 15)

VAR_INPUT

VAR_INPUT
    sIPAddr      : STRING(15);
    nTCPPort     : UINT:= MODBUS_TCP_PORT;
    nUnitID      : BYTE:=16#FF;
    nQuantity    : WORD;
    nMBAddr      : WORD;
    cbLength     : UDINT;
    pSrcAddr     : POINTER OF BYTE;
    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.

nQuantity: Number of digital outputs to be written (data bits). nQuantity must be > 0.

nMBAddr: Start address of the digital outputs to be written (bit offset).

cbLength: Contains the max. byte size of the source buffer containing the data to be written. The minimum buffer byte size must be: (nQuantity + 7) / 8.

pSrcAddr: Contains the address of the source buffer containing the data to be written. The buffer can be a single variable, an array or a structure, whose address can be found with the ADR operator.

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
    fbWriteCoils           : FB_MBWriteCoils;
    bWriteCoils            : BOOL;
    bWriteCoilsBusy        : BOOL;
    bWriteCoilsError       : BOOL;
    nWriteCoilsErrorId     : UDINT;
    nWriteCoilsCount       : UDINT;
    nQuantity              : WORD := 10;
    nMBAddr                : WORD := 14;
    arrData                : ARRAY [1..2] OF BYTE := 16#75,16#03;
END_VAR

After a rising edge of "bExecute" and successful execution of the ReadCoils command, the content of the arrData array is written to digital outputs 15 - 24:

Requirements