I set the bit 9 of S11 to wake up on UART. Is there any other way to go back to sleep apart from doing software reset?
This depends of the device you are programming on whether it has a sleep function implemented or not. Most programming devices have a function like this. It's advised to check your device's datasheet for more information regarding this issue. To be noted: you can create a function by yourself in which the system is in sleep mode and wake up when a signal reaches the bit 9.