AN2476 datasheet(43/49 Pages) STMICROELECTRONICS

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AN2476

Operating measurements

43/49

75x_mrcc.c

75x_eic.c

75x_extit.c

75x_cfg.c

Link all compiled files and load your image into Flash

Run the example

Note:

If the line #Define RTC_ON is modified through commenting/uncommenting in the

75x_conf.h file, the project must be rebuilt.

3.2.3

WFI mode

This example shows how to enter the system to WFI mode and wake-up from this mode

using an external Interrupt, an RTC Alarm or a NCKD(no clock detected) interrupt.

●

Choose the Board:

The chosen board for measurements can be selected in the 75x_conf.h file.

Uncomment the appropriate line:

#define STR750_EVAL

//#define Uniboard

●

Choose the WFI Mode:

Uncomment one of these lines in the 75x_conf.h file, to choose the required WFI mode

for the application:

//#define WFI_FLASH_Off

//#define WFI_FLASH_PowerDown

#define WFI_FLASH_On

In the associated software, the system clock is set to 64 MHz and an interrupt is generated

if no clock is present on OSC4M.

The EXTIT line7(P1.05) and EXTIT line15 are configured to generate interrupts on a rising

edge and the RTC is programmed to generate an interrupt each 1 second. The EXTIT

line15 is shared between the RTC_Alarm event and the WKP_STDBY pin (P1.15).

In the RTC interrupt handler, an LED connected to P2.18 pin is toggled and used to indicate

whether the MCU is in WFI or RUN mode.

The system enters WFI mode as follows:

After system is powered on, an LED connected to P2.18 pin is toggled each 1

second

After 5 seconds, the RTC is configured to generate an Alarm event with a trigger

delay of 10 seconds.

The system then enters WFI mode causing the P2.18 pin to stop toggling.

The system exits WFI mode as follows:

To wake-up from WFI mode a rising edge can be applied on EXTIT line15, EXTIT

line7 or the 4MHz external Quartz oscillator can be disconnected.

If within 10 seconds none of those actions are performed, the RTC Alarm wakes

the system up.

The P2.18 pin then restarts toggling and after 5 seconds the system enters WFI

mode again before exiting in the manner described above. This behavior is

repeated in an infinite loop.

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