RM0016 Auto-wakeup (AWU)
Doc ID 14587 Rev 8 115/449
12.3 AWU functional description
12.3.1 AWU operation
To use the AWU, perform the following steps in order:
1. Measure the LS clock frequency using the MSR bit in AWU_CSR register and TIM3 or
TIM1 input capture 1.
2. Define the appropriate prescaler value by writing to the APR [5:0] bits in the
Asynchronous prescaler register (AWU_APR).
3. Select the desired auto-wakeup delay by writing to the AWUTB[3:0] bits in the
Timebase selection register (AWU_TBR).
4. Set the AWUEN bit in the Control/status register (AWU_CSR).
5. Execute the HALT instruction. AWU counters are reloaded and start to count a new
AWU time interval.
Note: The counters only start when the MCU enters Active-halt mode after a HALT instruction
(refer to the Active-halt mode section in the power management chapter). The AWU
interrupt is then enabled at the same time.
The prescaler counter starts to count only if APR[5:0] value is different from its reset value,
0x3F.
Idle mode
If the AWU is not in use, then the AWUTB[3:0] bits the Timebase selection register
(AWU_TBR) should be loaded with 0b0000 to reduce power consumption.
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