FB_ModbusTcpRequest

VAR_INPUT

VAR_INPUT
    bStart       : BOOL;
    sRemoteIPAddr: STRING(15);
    iMyPortNo    : WORD;
    pReqBuff     : DWORD;
    cbReqLen     : WORD;
    pResBuff     : DWORD;
    cbResLen     : WORD;
END_VAR

bStart: the function block is activated by a rising edge at this input.

sRemoteIPAddr: this variable is a string containing the network address (IP address) of the remote partner.

iMyPortNo: the port number associated with the connection is passed here as a parameter. The port number is generated afresh (dynamically) each time the connection is established with the FB_ModbusTcpOpen function block.

pReqBuff : contains the address of the buffer with the MODBUS request data. It is the programmer who is responsible for dimensioning the buffer appropriately so that cbReqLen bytes can be removed from it. The buffer can be a single variable, an array or a structure, whose address can be found with the ADR operator.

cbReqLen : byte length of the MODBUS request data in the pReqBuff-buffer.

pResBuff : contains the address of the buffer with the MODBUS response data. The programmer is himself responsible for dimensioning the buffer to a size that can accept cbResLen bytes. The buffer can be a single variable, an array or a structure, whose address can be found with the ADR operator.

cbResLen : byte length of the MODBUS response buffer. It is the programmer who is responsible for dimensioning the buffer to such a size that all the response data can be accepted.

VAR_OUTPUT

VAR_OUTPUT
    bBusy       : BOOL;
    bError      : BOOL;
    iErrorId    : WORD;
    cbResponse  : WORD;
END_VAR

bBusy: if the function block is activated, this output is set. It remains set until a feedback is received.

bError: if an error should occur during the execution of the command, then this output is set, after the bBusy output has been reset.

iErrorId: supplies the command-specific error code (table) or the device-specific error code if the bError output is set.

cbResponse : the byte length of the response data actually returned in the response buffer.

Sample of calling the function block in FBD:

PROGRAM MAIN
VAR
    fbModbusRequest : FB_ModbusTcpRequest;
    bExecute        : BOOL;
    bExecute        : nConnectionPort;
    SendBuffer      : ARRAY[0..5] OF BYTE := 1,6,64,64,0,0;
    ReceiveBuffer   : ARRAY[0..255] OF BYTE;
    bBusy           : BOOL;
    bError          : BOOL;
    nErrId          : WORD;
    cbReceived      : WORD;
END_VAR

In this sample, a rising edge at the bExecute input causes a request to be sent to the remote partner with network address '172.16.2.209'.

Requirements