net.sourceforge.jmodbus
Class Modbus

java.lang.Object
  |
  +--net.sourceforge.jmodbus.Modbus

Direct Known Subclasses:

ModbusMaster, ModbusSlave

public class Modbus

extends java.lang.Object

Class to represent a Modbus device. This is a base class that will be extended by classes representing both Master and Slave implementations.

Field Summary

static int	ADDRESS_MAX Highest permissible address value.
static byte	COIL_OFF Command code to turn a single coil off.
static byte	COIL_ON Command code to turn a single coil on.
static int	debug Flag to adjust the debug output level at compile time.
static byte	EXCEPTION_MODIFIER Function code modfifer for exceptions.
static byte	ILLEGAL_DATA_ADDRESS Exception code to signify that the request contains an illegal data address.
static byte	ILLEGAL_DATA_VALUE Exception code to signify that the request contains an illegal data value.
static byte	ILLEGAL_FUNCTION Exception code to signify that the function code is unknown or illegal.
static byte	ILLEGAL_RESPONSE_LENGTH Exception code to signify that the request whould have generated an illegaly long response.
static int	MAX_MESSAGE_LENGTH Longest legal message length.
static byte	READ_COILS Command code to read multiple coils.
static byte	READ_EXCEPTION_STATUS Command code to read the exception status.
static byte	READ_INPUT_DISCRETES Command code to read read input discretes.
static byte	READ_INPUT_REGISTERS Command code to read imput registers.
static byte	READ_MULTIPLE_REGISTERS Command code to read multiple registers.
protected ModbusTransport	transport Modbus transport object that will be used to perform all communication of Modbus messages.
static int	UINT16_MAX The maximum value for a 16 bit unsigend integer.
static int	UINT16_MIN The minimum value for a 16 bit unsigned integer.
static int	UINT8_MAX The maximum value for a 8 bit unsigend integer.
static int	UINT8_MIN The minimum value for a 8 bit unsigned integer.
static byte	WRITE_COIL Command code to write a single coil.
static byte	WRITE_MULTIPLE_REGISTERS Command code to write multiple registers.
static byte	WRITE_SINGLE_REGISTER Command code to write a single register.

Constructor Summary

protected

Modbus(ModbusTransport transport) Class constructor.

Method Summary

boolean	receiveFrame(ModbusMessage msg) Method to receive a Modbus frame via the transport media.
boolean	sendFrame(ModbusMessage msg) Method to send a Modbus frame via the transport media.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

debug

public static final int debug

Flag to adjust the debug output level at compile time.

The debug levels are as follows:

• 0 - No debug output, systems runs silently
• 1 - Very basic debug information. Startup information and signals that a request or response cycle is starting
• 2 - Basic debug output. Basic send, receieve and processing messages from both messaging and transport levels.
• 3 - Detailed output of all operations but falling short of packet dumps.
• 4 - Verbose output. This includes full packet dumps at both messaging level and transport level.

READ_MULTIPLE_REGISTERS

public static final byte READ_MULTIPLE_REGISTERS

Command code to read multiple registers.

READ_INPUT_REGISTERS

public static final byte READ_INPUT_REGISTERS

Command code to read imput registers.

WRITE_MULTIPLE_REGISTERS

public static final byte WRITE_MULTIPLE_REGISTERS

Command code to write multiple registers.

WRITE_SINGLE_REGISTER

public static final byte WRITE_SINGLE_REGISTER

Command code to write a single register.

READ_COILS

public static final byte READ_COILS

Command code to read multiple coils.

WRITE_COIL

public static final byte WRITE_COIL

Command code to write a single coil.

READ_INPUT_DISCRETES

public static final byte READ_INPUT_DISCRETES

Command code to read read input discretes.

COIL_OFF

public static final byte COIL_OFF

Command code to turn a single coil off.

COIL_ON

public static final byte COIL_ON

Command code to turn a single coil on.

READ_EXCEPTION_STATUS

public static final byte READ_EXCEPTION_STATUS

Command code to read the exception status.

EXCEPTION_MODIFIER

public static final byte EXCEPTION_MODIFIER

Function code modfifer for exceptions. This value is added to the function code to signify that some sort of error has occured in the function

ILLEGAL_FUNCTION

public static final byte ILLEGAL_FUNCTION

Exception code to signify that the function code is unknown or illegal.

ILLEGAL_DATA_ADDRESS

public static final byte ILLEGAL_DATA_ADDRESS

Exception code to signify that the request contains an illegal data address.

ILLEGAL_DATA_VALUE

public static final byte ILLEGAL_DATA_VALUE

Exception code to signify that the request contains an illegal data value.

ILLEGAL_RESPONSE_LENGTH

public static final byte ILLEGAL_RESPONSE_LENGTH

Exception code to signify that the request whould have generated an illegaly long response.

ADDRESS_MAX

public static final int ADDRESS_MAX

Highest permissible address value. This corresponds to a full scale 16 bit unsigned integer.

MAX_MESSAGE_LENGTH

public static final int MAX_MESSAGE_LENGTH

Longest legal message length.

UINT16_MAX

public static int UINT16_MAX

The maximum value for a 16 bit unsigend integer.

UINT16_MIN

public static int UINT16_MIN

The minimum value for a 16 bit unsigned integer.

UINT8_MAX

public static int UINT8_MAX

The maximum value for a 8 bit unsigend integer.

UINT8_MIN

public static int UINT8_MIN

The minimum value for a 8 bit unsigned integer.

transport

protected ModbusTransport transport

Modbus transport object that will be used to perform all communication of Modbus messages.

Constructor Detail

Modbus

protected Modbus(ModbusTransport transport)

Class constructor. This passes the class a ModbusTransport object that will be used for communications.

Parameters:

transport - The ModbusTransport object that should be used by this Modbus object to send and receive Modbus frames.

Method Detail

sendFrame

public boolean sendFrame(ModbusMessage msg)

Method to send a Modbus frame via the transport media. The return status of the function indicates if the transmission sucedded. The frame is send via the underlying transport mechanisim.

Parameters:

msg - The Modbus Message to be sent.

Returns:

Transmission sucess flag, to indicate if the transmission was sucessful.

receiveFrame

public boolean receiveFrame(ModbusMessage msg)

Method to receive a Modbus frame via the transport media. The return value indicates the length of the frame. This method will block until the comminication path is terminated or a frame is sucessfully received. The frame is received from the underlying transport mechanisim.

Parameters:

msg - The Modbus Message object for received data to be written into

Returns:

Receive sucess flag, to indicate if the receive was sucessful.