FieldTalk^™ Modbus^® Slave Library
C++ Editions

Server Functions common to all Protocol Flavours

Detailed Description

The FieldTalk Modbus Slave Protocol Library's server engine implements the most commonly used Modbus data functions as well as some control functions. The functions to perform PLC program download and other device specific functions are outside the scope of this library.

All Bit Access and 16 Bits Access Modbus Function Codes have been implemented. In addition the most frequently used Diagnostics Function Codes have been implemented.

The following table lists the functions supported by the slave:

Modbus Function Code	Current Terminology	Classic Terminology
16-bit Access
3	Read Multiple Registers	Read Holding Registers
4	Read Input Registers	Read Input Registers
6	Write Single Register	Preset Single Register
16 (10 Hex)	Write Multiple Registers	Preset Multiple Registers
22 (16 Hex)	Mask Write Register	Mask Write Register
23 (17 Hex)	Read/Write Registers	Read/Write Registers
Bit access
1	Read Coils	Read Coil Status
2	Read Inputs Discretes	Read Input Status
5	Write Coil	Force Single Coil
15 (0F Hex)	Force Multiple Coils	Force Multiple Coils
Diagnostics
7	Read Exception Status	Read Exception Status
8 sub code 00	Diagnostics - Return Query Data	Diagnostics - Return Query Data


Server Management Functions
int	MbusSlaveServer::addDataTable (int slaveAddr, MbusDataTableInterface *dataTablePtr)
	Associates a protocol object with a Data Provider and a slave address.
virtual int	MbusSlaveServer::serverLoop ()=0
	Modbus slave server loop.
virtual void	MbusSlaveServer::shutdownServer ()
	Shuts down the Modbus Server.
virtual int	MbusSlaveServer::isStarted ()=0
	Returns if server has been started up.
virtual int	MbusSlaveServer::getConnectionStatus ()=0
	Associates a protocol object with a Data Provider and a slave address.
Protocol Configuration
long	MbusSlaveServer::setTimeout (long timeOut)
	Configures master transmit time-out supervision.
long	MbusSlaveServer::getTimeout ()
	Returns the master time-out supervision value.
Transmission Statistic Functions
unsigned long	MbusSlaveServer::getTotalCounter ()
	Returns how often a message transfer has been executed.
void	MbusSlaveServer::resetTotalCounter ()
	Resets total message transfer counter.
unsigned long	MbusSlaveServer::getSuccessCounter ()
	Returns how often a message transfer was successful.
void	MbusSlaveServer::resetSuccessCounter ()
	Resets successful message transfer counter.
Utility Functions
static char *	MbusSlaveServer::getPackageVersion ()
	Returns the package version number.

Function Documentation

int addDataTable	(	int	slaveAddr,
		MbusDataTableInterface *	dataTablePtr
	)	`[inherited]`

Associates a protocol object with a Data Provider and a slave address.

Parameters:

dataTablePtr

Modbus data table pointer. Must point to a Data Provider object derived from the MbusDataTableInterface class. The Data Provider is the interface between your application data and the Modbus network.

Returns:: FTALK_SUCCESS on success or error code. See Protocol Errors and Exceptions for a list of error codes.

long setTimeout ( long timeOut ) [inherited]

Configures master transmit time-out supervision.

The slave can monitor whether a master is actually transmitting characters or not. This function sets the transmit time-out to the specified value. A value of 0 disables the time-out, which stops time-out notifications being sent to the Data Provider.

Remarks:: The time-out value is indicative only and not guaranteed to be maintained. How precise it is followed depends on the operating system used, it's scheduling priority and it's system timer resolution.

Note:: The time-out does not check if a master is sending valid frames.

Parameters:

timeOut

Timeout value in ms (Range: 0 - 100000), 0 disables time-out

Return values:

	FTALK_SUCCESS	Success
	FTALK_ILLEGAL_ARGUMENT_ERROR	Argument out of range

unsigned long getTotalCounter ( ) [inherited]

Returns how often a message transfer has been executed.

Returns:: Counter value

char * getPackageVersion ( ) [static, inherited]

Returns the package version number.

Returns:: Package version string

long getTimeout ( ) [inherited]

Returns the master time-out supervision value.

Remarks:: The time-out value is indicative only and not guaranteed to be maintained. How precise it is followed depends on the operating system used, it's scheduling priority and it's system timer resolution.

Returns:: Timeout value in ms

unsigned long getSuccessCounter ( ) [inherited]

Returns how often a message transfer was successful.

Returns:: Counter value

virtual int serverLoop ( ) [pure virtual, inherited]

Modbus slave server loop.

This server loop must be called continuously. It must not be blocked. The server has to be started before calling the serverLoop() method.

In most cases the server loop is executed in an endless loop:

 while (1)
 {
   mbusProtocol.serverLoop();
   doOtherStuff();
 }

Returns:: FTALK_SUCCESS on success or error code. See Protocol Errors and Exceptions for a list of error codes.

Implemented in MbusRtuSlaveProtocol, MbusAsciiSlaveProtocol, and MbusTcpSlaveProtocol.

void shutdownServer ( ) [virtual, inherited]

Shuts down the Modbus Server.

This function also closes any associated serial ports or sockets.

Reimplemented in MbusSerialSlaveProtocol, and MbusTcpSlaveProtocol.

virtual int isStarted ( ) [pure virtual, inherited]

Returns if server has been started up.

Return values:

	true	= started
	false	= shutdown

Implemented in MbusSerialSlaveProtocol, and MbusTcpSlaveProtocol.

virtual int getConnectionStatus ( ) [pure virtual, inherited]

Associates a protocol object with a Data Provider and a slave address.

Parameters:

dataTablePtr

Modbus data table pointer. Must point to a Data Provider object derived from the MbusDataTableInterface class. The Data Provider is the interface between your application data and the Modbus network.

Returns:: FTALK_SUCCESS on success or error code. See Protocol Errors and Exceptions for a list of error codes.

Implemented in MbusSerialSlaveProtocol, and MbusTcpSlaveProtocol.

Server Functions common to all Protocol Flavours

Detailed Description

Server Management Functions

Protocol Configuration

Transmission Statistic Functions

Utility Functions

Function Documentation