Microcontroller as slave, ACK problem

enum commands {
    start=0,
    addr,
    recieve,
    write,
    stop};

void __attribute__((interrupt,no_auto_psv)) _SI2C1Interrupt(void) {

//void i2c(){
    I2C1ADD = SLAVE_ADRESS;
    static unsigned char *d = 0x00;
    unsigned char data_t = 0xFF;
    static unsigned char cmd = start;

    slave:
    switch(cmd) {
        case start:
            if(I2C1STATbits.S)                              //start bit arrived
                cmd = addr;
            else if(I2C1STATbits.P) {                       //stop bit arrived
                cmd = start;
                goto slave;}
 /*****************************************************************************/
        case addr:
            if(!I2C1STATbits.D_A)    {                       // data recieved
                if(!I2C1STATbits.R_W){
                    _TRISB5 = 1;
                    cmd = recieve;
                }
               else if(I2C1STATbits.R_W){
                    _TRISB5 = 0;
                    cmd = write;
                  }
            }
            else cmd = recieve;                            // adress recieved,
            break;
/******************************************************************************/
        case recieve:
            while(!I2C1STATbits.RBF);
            *d = I2C1RCV;
            cmd = start;
            break;
/******************************************************************************/
        case write:
            I2C1TRN = data_t;
            while(I2C1STATbits.TBF);
            cmd = start;
 /*****************************************************************************/
    }
    _SI2C1IF = 0;
    goto slave;
}