AN2629 datasheet(27/43 Pages) STMICROELECTRONICS

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AN2629

Power and wakeup time measurement

Doc ID 13922 Rev 2

27/43

5.3.2

Detailed description

The wakeup time is defined as follows:

●

For Sleep and Stop modes: the wakeup time starts on setting the wakeup source (in

our case the Wakeup push-button of the STM3210B-EVAL board connected to pin

PA0) and ends:

–

after the execution of the first instruction after the WFE (in the case of wakeup on

an external event) or

–

after the execution of the first instruction of the interrupt service routine (in the

case of wakeup on an external interrupt)

●

Standby mode: after waking up from Standby mode, program execution restarts in the

same way as after a Reset. So the wakeup time for the Standby mode is the time

between the selection of the wakeup source (Wakeup push-button) and the execution

of the first instruction of the code.

Note:

For more details on the different low-power modes please refer to Section 1: Power supply.

Hardware environment

Pin PC6 is set to one after wakeup from the low-power modes, so, to measure the wakeup

time, an oscilloscope should be connected across the PC6 and PA0 pins. The wakeup time

is the time between the rising edge of PA0 (Wakeup button) and the rising edge of PC6.

Firmware description

The firmware provided is divided into the following files:

●

main.c:

This file contains the main Firmware body. The user can select the low-power mode to

test by uncommenting the respective line:

/* Define the Low power mode*/

//#define SLEEP

//#define STOP_Regulator_ON

//#define STOP_Regulator_LowPower

//#define STANDBY

Before entering a low-power mode, PC6 is configured as an output push-pull (speed

50 MHz) and reset to the low level.

For the Sleep and Stop modes:

–

in the case of WFE, a direct write to the BSRR (Bit Set Reset register) is

performed to set PC6 to the high level

–

in case of WFI, the setting of PC6 is managed on the interrupt service routine of

the EXTI line 0

For the Standby mode, pin PC6 should be set at the code startup (this part of the

code is managed in the startup files. See below).

●

tools startup file:

To measure the wakeup time for the Standby mode, it is first necessary to configure

and set the PC6 pin. To manage this, the following asm code is added to the tools

startup file:

; Set clock GPIOC (APB)

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