FB_MBUdpWriteCoils (Modbus function 15)
This function is used for writing 1 to 2048 digital outputs (coils). One digital output corresponds to one bit of the write data bytes.
VAR_INPUT
VAR_INPUT
sIPAddr : STRING(15);
nTCPPort : UINT:= MODBUS_TCP_PORT;
nUnitID : BYTE:=16#FF;
nQuantity : WORD;
nMBAddr : WORD;
cbLength : UDINT;
pSrcAddr : UDINT;
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;
cbRead : 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.
Function specific ADS error code | Possible reason |
---|---|
0x8001 | Modbus function not implemented |
0x8002 | Invalid address or length |
0x8003 | Invalid parameters: - wrong number of registers |
0x8004 | Modbus server error |
Requirements
Development environment | Target system type | PLC libraries to be linked |
---|---|---|
TwinCAT v2.8.0 | PC (i386) | TcModbusSrv.Lib |