UART sleep configure register 0
| WK_CHAR1 | This register restores the specified wake up char1 to wake up |
| WK_CHAR2 | This register restores the specified wake up char2 to wake up |
| WK_CHAR3 | This register restores the specified wake up char3 to wake up |
| WK_CHAR4 | This register restores the specified wake up char4 to wake up |