I2CDR
I2C_WRITE(I2CDR, addr_byte);
I2C_WRITE(I2CDR, *cmdptr++);
I2C_WRITE(I2CDR, addr_byte);
(void)I2C_READ(I2CDR); /* dummy read */
*dataptr++ = I2C_READ(I2CDR);
(void)I2C_READ(I2CDR); /* dummy read */
I2C_WRITE(I2CDR, *dataptr++);