public int customFunction(
	int slaveAddr,
	int functionCode,
	byte[] requestData,
	ref byte[] responseData
)

Public Function customFunction ( 
	slaveAddr As Integer,
	functionCode As Integer,
	requestData As Byte(),
	ByRef responseData As Byte()
) As Integer

public:
int customFunction(
	int slaveAddr, 
	int functionCode, 
	array<unsigned char>^ requestData, 
	array<unsigned char>^% responseData
)

Parameters

slaveAddr

Type: SystemInt32
Modbus address of slave device or unit identifier (Range: 1 - 255 for serial, 0 - 255 for TCP)

functionCode

Type: SystemInt32
Custom function code to be used for Modbus transaction (Range: 1-127)

requestData

Type: SystemByte
Array with data to be sent as request (not including slave address or function code). The length of the array determines how many request bytes are sent (Range: 0-252).

responseData

Type: SystemByte
Buffer which will be filled with the response data. The buffer must be large enough to hold the reply data. (Range: 0-252) The length will be adjusted should the actual response data be less. A FTALK_INSUFFICIENT_BUFFER error code will be returned in case the allocated buffer size was insufficient.

Return Value

The modbus specification reserves function codes 65-72 and 100-110 for user defined functions.

Reference