AN2476 datasheet(42/49 Pages) STMICROELECTRONICS

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Operating measurements

AN2476

42/49

After the clock configuration (system clock set to 60 MHz), the P2.18 pin restarts

toggling and in 5 seconds the system enters STOP mode again before exiting in

the manner described above.

This behavior is repeated in an infinite loop.

●

If RTC is not on (by commenting the line #define RTC_ON in the 75x_conf.h file):

The EXTIT line7(P1.05) and EXTIT line15 ( WKP_STDBY pin P1.15) are configured to

generate interrupts on a rising edge.

An LED connected to P2.18 pin is switched on to indicate when the MCU is in RUN

mode.

The system enters STOP mode as follows:

After system power on, an LED connected to P2.18 pin is switched on.

When a falling edge is detected on EXTIT line7 the system enters STOP mode

causing the P2.18 pin to switch off the LED.

The system exits STOP mode as follows:

To wake-up from STOP mode, either a rising edge can be applied on EXTIT

line15, EXTIT line7 or the 4MHz external Quartz oscillator can be disconnected.

The LED connected to P0.16 is switched on and the VCO of the PLL (FREEOSC)

supplies the system clock.

After the clock configuration (system clock set to 60 MHz), the LED connected to

P2.18 pin is switched on.

When the 4MHz external Quartz oscillator is disconnected, the VCO of the PLL (FREEOSC)

supplies the system clock. Once the 4MHz clock has recovered (by connecting the 4MHz

Quartz oscillator) the system clock is reconfigured to 60 MHz.

If the system fails to enter STOP mode, a led connected to P2.19 pin is turned on.

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Directory contents:

–

75x_conf.h Library Configuration file

–

75x_it.c

Interrupt handlers

–

main.c

Main program

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Hardware environment:

–

Connect three LEDS to P016, P2.18 and P2.19 pins (respectively LD3, LD4 and

LD5 on STR75x-EVAL board).

–

Connect a push-button to WKP_STDBY pin (P1.15) (the wakeup push-button on

STR75x-EVAL board).

–

Connect a push-button to EXTIT line7 pin (P1.05) (the key push-button on

STR75x-EVAL board).

–

On STR75x-EVAL board the 4MHz Quartz oscillator is mounted on socket so it is

easy to disconnect.

●

How to use it:

In order to make the program work, you must do the following :

Create a project and setup all your toolchain's start-up files

Compile the directory content files and required Library files :

75x_lib.c

75x_rtc.c

75x_gpio.c

AN2476 Datasheet(PDF) 42 Page - STMicroelectronics

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