* \brief The main pooling loop of the Modbus protocol stack.
 *
 * This function must be called periodically. The timer interval required
 * is given by the application dependent Modbus slave timeout. Internally the
 * function calls xMBPortEventGet() and waits for an event from the receiver or
 * transmitter state machines. 
 *
 * \return If the protocol stack is not in the enabled state the function
 *   returns eMBErrorCode::MB_EILLSTATE. Otherwise it returns 
 *   eMBErrorCode::MB_ENOERR.
 */
eMBErrorCode    eMBPoll( void );

/*! \ingroup modbus
 * \brief Configure the slave id of the device.
 *
 * This function should be called when the Modbus function <em>Report Slave ID</em>
 * is enabled ( By defining MB_FUNC_OTHER_REP_SLAVEID_ENABLED in mbconfig.h ).
 *
 * \param ucSlaveID Values is returned in the <em>Slave ID</em> byte of the
 *   <em>Report Slave ID</em> response.
 * \param xIsRunning If TRUE the <em>Run Indicator Status</em> byte is set to 0xFF.
 *   otherwise the <em>Run Indicator Status</em> is 0x00.
 * \param pucAdditional Values which should be returned in the <em>Additional</em>
 *   bytes of the <em> Report Slave ID</em> response.
 * \param usAdditionalLen Length of the buffer <code>pucAdditonal</code>.
 *
 * \return If the static buffer defined by MB_FUNC_OTHER_REP_SLAVEID_BUF in
 *   mbconfig.h is to small it returns eMBErrorCode::MB_ENORES. Otherwise
 *   it returns eMBErrorCode::MB_ENOERR.
 */
eMBErrorCode    eMBSetSlaveID( UCHAR ucSlaveID, BOOL xIsRunning,
                               UCHAR const *pucAdditional,
                               USHORT usAdditionalLen );

/*! \ingroup modbus
 * \brief Registers a callback handler for a given function code.
 *
 * This function registers a new callback handler for a given function code.
 * The callback handler supplied is responsible for interpreting the Modbus PDU and
 * the creation of an appropriate response. In case of an error it should return
 * one of the possible Modbus exceptions which results in a Modbus exception frame
 * sent by the protocol stack. 
 *
 * \param ucFunctionCode The Modbus function code for which this handler should
 *   be registers. Valid function codes are in the range 1 to 127.
 * \param pxHandler The function handler which should be called in case
 *   such a frame is received. If \c NULL a previously registered function handler
 *   for this function code is removed.
 *
 * \return eMBErrorCode::MB_ENOERR if the handler has been installed. If no
 *   more resources are available it returns eMBErrorCode::MB_ENORES. In this
 *   case the values in mbconfig.h should be adjusted. If the argument was not
 *   valid it returns eMBErrorCode::MB_EINVAL.
 */
eMBErrorCode    eMBRegisterCB( UCHAR ucFunctionCode, 
                               pxMBFunctionHandler pxHandler );

/* ----------------------- Callback -----------------------------------------*/

/*! \defgroup modbus_registers Modbus Registers
 * \code #include "mb.h" \endcode
 * The protocol stack does not internally allocate any memory for the
 * registers. This makes the protocol stack very small and also usable on
 * low end targets. In addition the values don't have to be in the memory
 * and could for example be stored in a flash.<br>
 * Whenever the protocol stack requires a value it calls one of the callback
 * function with the register address and the number of registers to read
 * as an argument. The application should then read the actual register values
 * (for example the ADC voltage) and should store the result in the supplied
 * buffer.<br>
 * If the protocol stack wants to update a register value because a write
 * register function was received a buffer with the new register values is
 * passed to the callback function. The function should then use these values
 * to update the application register values.
 */

/*! \ingroup modbus_registers
 * \brief Callback function used if the value of a <em>Input Register</em>
 *   is required by the protocol stack. The starting register address is given
 *   by \c usAddress and the last register is given by <tt>usAddress +
 *   usNRegs - 1</tt>.
 *
 * \param pucRegBuffer A buffer where the callback function should write
 *   the current value of the modbus registers to.
 * \param usAddress The starting address of the register. Input registers
 *   are in the range 1 - 65535.
 * \param usNRegs Number of registers the callback function must supply.
 *
 * \return The function must return one of the following error codes:
 *   - eMBErrorCode::MB_ENOERR If no error occurred. In this case a normal
 *       Modbus response is sent.
 *   - eMBErrorCode::MB_ENOREG If the application can not supply values
 *       for registers within this range. In this case a 
 *       <b>ILLEGAL DATA ADDRESS</b> exception frame is sent as a response.
 *   - eMBErrorCode::MB_ETIMEDOUT If the requested register block is
 *       currently not available and the application dependent response
 *       timeout would be violated. In this case a <b>SLAVE DEVICE BUSY</b>
 *       exception is sent as a response.
 *   - eMBErrorCode::MB_EIO If an unrecoverable error occurred. In this case
 *       a <b>SLAVE DEVICE FAILURE</b> exception is sent as a response.
 */
eMBErrorCode    eMBRegInputCB( UCHAR * pucRegBuffer, USHORT usAddress,
                               USHORT usNRegs );

/*! \ingroup modbus_registers
 * \brief Callback function used if a <em>Holding Register</em> value is
 *   read or written by the protocol stack. The starting register address
 *   is given by \c usAddress and the last register is given by
 *   <tt>usAddress + usNRegs - 1</tt>.
 *
 * \param pucRegBuffer If the application registers values should be updated the
 *   buffer points to the new registers values. If the protocol stack needs
 *   to now the current values the callback function should write them into
 *   this buffer.
 * \param usAddress The starting address of the register.
 * \param usNRegs Number of registers to read or write.
 * \param eMode If eMBRegisterMode::MB_REG_WRITE the application register 
 *   values should be updated from the values in the buffer. For example
 *   this would be the case when the Modbus master has issued an 
 *   <b>WRITE SINGLE REGISTER</b> command.
 *   If the value eMBRegisterMode::MB_REG_READ the application should copy 
 *   the current values into the buffer \c pucRegBuffer.
 *
 * \return The function must return one of the following error codes:
 *   - eMBErrorCode::MB_ENOERR If no error occurred. In this case a normal
 *       Modbus response is sent.
 *   - eMBErrorCode::MB_ENOREG If the application can not supply values
 *       for registers within this range. In this case a 
 *       <b>ILLEGAL DATA ADDRESS</b> exception frame is sent as a response.
 *   - eMBErrorCode::MB_ETIMEDOUT If the requested register block is
 *       currently not available and the application dependent response
 *       timeout would be violated. In this case a <b>SLAVE DEVICE BUSY</b>
 *       exception is sent as a response.
 *   - eMBErrorCode::MB_EIO If an unrecoverable error occurred. In this case
 *       a <b>SLAVE DEVICE FAILURE</b> exception is sent as a response.
 */
eMBErrorCode    eMBRegHoldingCB( UCHAR * pucRegBuffer, USHORT usAddress,
                                 USHORT usNRegs, eMBRegisterMode eMode );

/*! \ingroup modbus_registers
 * \brief Callback function used if a <em>Coil Register</em> value is
 *   read or written by the protocol stack. If you are going to use
 *   this function you might use the functions xMBUtilSetBits(  ) and
 *   xMBUtilGetBits(  ) for working with bitfields.
 *
 * \param pucRegBuffer The bits are packed in bytes where the first coil
 *   starting at address \c usAddress is stored in the LSB of the
 *   first byte in the buffer <code>pucRegBuffer</code>.
 *   If the buffer should be written by the callback function unused
 *   coil values (I.e. if not a multiple of eight coils is used) should be set
 *   to zero.
 * \param usAddress The first coil number.
 * \param usNCoils Number of coil values requested.
 * \param eMode If eMBRegisterMode::MB_REG_WRITE the application values should
 *   be updated from the values supplied in the buffer \c pucRegBuffer.
 *   If eMBRegisterMode::MB_REG_READ the application should store the current
 *   values in the buffer \c pucRegBuffer.
 *
 * \return The function must return one of the following error codes:
 *   - eMBErrorCode::MB_ENOERR If no error occurred. In this case a normal
 *       Modbus response is sent.
 *   - eMBErrorCode::MB_ENOREG If the application does not map an coils
 *       within the requested address range. In this case a 
 *       <b>ILLEGAL DATA ADDRESS</b> is sent as a response.
 *   - eMBErrorCode::MB_ETIMEDOUT If the requested register block is
 *       currently not available and the application dependent response
 *       timeout would be violated. In this case a <b>SLAVE DEVICE BUSY</b>
 *       exception is sent as a response.
 *   - eMBErrorCode::MB_EIO If an unrecoverable error occurred. In this case
 *       a <b>SLAVE DEVICE FAILURE</b> exception is sent as a response.
 */
eMBErrorCode    eMBRegCoilsCB( UCHAR * pucRegBuffer, USHORT usAddress,
                               USHORT usNCoils, eMBRegisterMode eMode );

/*! \ingroup modbus_registers
 * \brief Callback function used if a <em>Input Discrete Register</em> value is
 *   read by the protocol stack.
 *
 * If you are going to use his function you might use the functions
 * xMBUtilSetBits(  ) and xMBUtilGetBits(  ) for working with bitfields.
 *
 * \param pucRegBuffer The buffer should be updated with the current
 *   coil values. The first discrete input starting at \c usAddress must be
 *   stored at the LSB of the first byte in the buffer. If the requested number
 *   is not a multiple of eight the remaining bits should be set to zero.
 * \param usAddress The starting address of the first discrete input.
 * \param usNDiscrete Number of discrete input values.
 * \return The function must return one of the following error codes:
 *   - eMBErrorCode::MB_ENOERR If no error occurred. In this case a normal
 *       Modbus response is sent.
 *   - eMBErrorCode::MB_ENOREG If no such discrete inputs exists.
 *       In this case a <b>ILLEGAL DATA ADDRESS</b> exception frame is sent 
 *       as a response.
 *   - eMBErrorCode::MB_ETIMEDOUT If the requested register block is
 *       currently not available and the application dependent response
 *       timeout would be violated. In this case a <b>SLAVE DEVICE BUSY</b>
 *       exception is sent as a response.
 *   - eMBErrorCode::MB_EIO If an unrecoverable error occurred. In this case
 *       a <b>SLAVE DEVICE FAILURE</b> exception is sent as a response.
 */
eMBErrorCode    eMBRegDiscreteCB( UCHAR * pucRegBuffer, USHORT usAddress,
                                  USHORT usNDiscrete );

#ifdef __cplusplus
PR_END_EXTERN_C
#endif
#endif