BYTE volatile byTWIctrl;
BYTE volatile byTWIstate;

      // State byte. Default set to TWI_NO_STATE.
static BYTE* pTWItrans;         // указатель на текущий байт
static BYTE ctTWI;             // счетчик приема-передачи
static BYTE byDisp;            // смещение в подчиненном устройстве
static BYTE bySlaveAddr;

..............................................................
  функции всякие разные
..................................................................
// сам поток собственно

SIGNAL(SIG_2WIRE_SERIAL){
    switch (TWSR){
    //------------------------------------------------------------------------
        case TWI_START:             // START has been transmitted
        case TWI_REP_START:         // Repeated START has been transmitted
                    TWDR = bySlaveAddr;
            if(byTWIctrl & TWS_READ_NOW)  TWDR |= 1;
                     TWCR = (1<<TWEN)|                                 // TWI Interface enabled
                            (1<<TWIE)|(1<<TWINT)|                      // Enable TWI Interupt and clear the flag to send byte
                               (0<<TWEA)|(0<<TWSTA)|(0<<TWSTO)|           //
                               (0<<TWWC);
                break;
    //------------------------------------------------------------------------
        case TWI_MTX_ADR_ACK:       // SLA+W has been tramsmitted and ACK received
                TWDR = byDisp;
                TWCR = (1<<TWEN)|                                 // TWI Interface enabled
                        (1<<TWIE)|(1<<TWINT)|                      // Enable TWI Interupt and clear the flag to send byte
                           (0<<TWEA)|(0<<TWSTA)|(0<<TWSTO)|           //
                           (0<<TWWC);
            break;
    //----------------------------------------------------------------------
        case TWI_MTX_DATA_ACK:      // Data byte has been tramsmitted and ACK received
            if(byTWIctrl & TWS_READ_OP){ // проверка на операцию записи
                       byTWIctrl |= TWS_READ_NOW;
                    TWCR = (1<<TWEN)|                             // TWI Interface enabled.
                            (1<<TWIE)|(1<<TWINT)|                  // Enable TWI Interupt and clear the flag.
                            (0<<TWEA)|(1<<TWSTA)|(0<<TWSTO)|       // Initiate a START condition.
                            (0<<TWWC);
                break;
            }
              if (ctTWI){        // передача данных
                    ctTWI--;
                    TWDR = *pTWItrans;
                pTWItrans++;
                TWCR = (1<<TWEN)|                                 // TWI Interface enabled
                        (1<<TWIE)|(1<<TWINT)|                      // Enable TWI Interupt and clear the flag to send byte
                           (0<<TWEA)|(0<<TWSTA)|(0<<TWSTO)|           //
                           (0<<TWWC);                                 //
              }else{                    // Send STOP after last byte
                    byTWIctrl = 0;                 // Set status bits to completed successfully.
                    TWCR = (1<<TWEN)|                                 // TWI Interface enabled
                               (0<<TWIE)|(1<<TWINT)|                      // Disable TWI Interrupt and clear the flag
                               (0<<TWEA)|(0<<TWSTA)|(1<<TWSTO)|           // Initiate a STOP condition.
                               (0<<TWWC);                                 //
              }
              break;
    //-----------------------------------------------------------------------------
        case TWI_MRX_DATA_ACK:      // Data byte has been received and ACK tramsmitted
                  *pTWItrans = TWDR;
                pTWItrans++;
        case TWI_MRX_ADR_ACK:       // SLA+R has been tramsmitted and ACK received
                ctTWI--;
              if (ctTWI){                  // Detect the last byte to NACK it.
                    TWCR = (1<<TWEN)|                                 // TWI Interface enabled
                               (1<<TWIE)|(1<<TWINT)|                      // Enable TWI Interupt and clear the flag to read next byte
                               (1<<TWEA)|(0<<TWSTA)|(0<<TWSTO)|           // Send ACK after reception
                               (0<<TWWC);                                 //
              }else{                    // Send NACK after next reception
                    TWCR = (1<<TWEN)|                                 // TWI Interface enabled
                               (1<<TWIE)|(1<<TWINT)|                      // Enable TWI Interupt and clear the flag to read next byte
                               (0<<TWEA)|(0<<TWSTA)|(0<<TWSTO)|           // Send NACK after reception
                               (0<<TWWC);                                 //
              }
              break;
        case TWI_MRX_DATA_NACK:     // Data byte has been received and NACK tramsmitted
                  *pTWItrans = TWDR;
                  byTWIctrl = 0;                 // Set status bits to completed successfully.
                  TWCR = (1<<TWEN)|                                 // TWI Interface enabled
                         (0<<TWIE)|(1<<TWINT)|                      // Disable TWI Interrupt and clear the flag
                         (0<<TWEA)|(0<<TWSTA)|(1<<TWSTO)|           // Initiate a STOP condition.
                         (0<<TWWC);                                 //
              break;
        case TWI_ARB_LOST:          // Arbitration lost
                byTWIctrl = 0;
                  TWCR = (1<<TWEN)|                                 // TWI Interface enabled
                          (1<<TWIE)|(1<<TWINT)|                      // Enable TWI Interupt and clear the flag
                          (0<<TWEA)|(1<<TWSTA)|(0<<TWSTO)|           // Initiate a (RE)START condition.
                          (0<<TWWC);                                 //
                  break;
//        case TWI_MTX_ADR_NACK:      // SLA+W has been tramsmitted and NACK received
//        case TWI_MRX_ADR_NACK:      // SLA+R has been tramsmitted and NACK received
//        case TWI_MTX_DATA_NACK:     // Data byte has been tramsmitted and NACK received
        //    case TWI_NO_STATE              // No relevant state information available; TWINT = “0”
//        case TWI_BUS_ERROR:         // Bus error due to an illegal START or STOP condition
        default:
                      byTWIstate = TWSR;                                     // Store TWSR and automatically sets clears noErrors bit.
                    byTWIctrl = 0;                                    // Reset TWI Interface
                      TWCR = (1<<TWEN)|                                 // Enable TWI-interface and release TWI pins
                             (0<<TWIE)|(0<<TWINT)|                      // Disable Interupt
                             (0<<TWEA)|(0<<TWSTA)|(0<<TWSTO)|           // No Signal requests
                             (0<<TWWC);                                 //
    }
}