FIFO status register.
| RXFIFO_RADDR | This is the offset address of the APB reading from rxfifo |
| RXFIFO_WADDR | This is the offset address of i2c module receiving data and writing to rxfifo. |
| TXFIFO_RADDR | This is the offset address of i2c module reading from txfifo. |
| TXFIFO_WADDR | This is the offset address of APB bus writing to txfifo. |
| SLAVE_RW_POINT | The received data in I2C slave mode. |