RM0312 datasheet(85/275 Pages) STMICROELECTRONICS

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RM0312

Auto-wakeup (AWU)

12.3

AWU functional description

12.3.1

AWU operation

To use the AWU, perform the following steps in order:

Measure the LS clock frequency using the MSR bit in AWU_CSR register and TIM

input capture 1.

Define the appropriate prescaler value by writing to the APR [5:0] bits in the

Asynchronous prescaler register (AWU_APR).

Select the desired auto-wakeup delay by writing to the AWUTB[3:0] bits in the

Timebase selection register (AWU_TBR).

Set the AWUEN bit in the Control/status register (AWU_CSR).

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.

RM0312 数据表(PDF) 85 Page - STMicroelectronics