WFI in LowPowerMode

Posted on June 24, 2005 at 05:23

Hi to all.

I have a problem entering in LPWFI: the Main Voltage Regulator is alwais ON, even if bit LPVRWFI is set.

I have made many tests with the same result: the power consumption is too much large!!

For example:

Standby (or powerdown) mode: 800 uA (ARM + rest of board - all PIO in HI)

LPWFI: 2600 uA (ARM + rest of board - all PIO in HI)

This is a source code:

void MySuspend(void)

{

volatile u32 Tmp;

// port in HighImpedence

GPIO_Config(GPIO0, 0xFF, GPIO_HI_AIN_TRI); //

GPIO_Config(GPIO1, 0xFF, GPIO_HI_AIN_TRI); //

// Set LPM in WFI mode

Tmp = RCCU->CLKCTL | 0x01;

RCCU->CLKCTL = Tmp;

// Select CK_AF in LPM

Tmp = RCCU->CLKCTL | 0x02;

RCCU->CLKCTL = Tmp;

// Select 32KHz clock

Tmp = RCCU->CLKCTL | 0x04; // bit 2 - CKAF_SEL

RCCU->CLKCTL = Tmp;

// switch off the PLL1

RCCU->PLLCONF &= ~RCCU_FREEN_Mask; // free running

RCCU->PLLCONF |= 0x07; // stop PLL1

// Power OFF external 4MHz oscillator

GPIO_Config(GPIO1, 0x08, GPIO_OUT_PP); // P1.3 -->> PushPull

GPIO_BitWrite(GPIO1, 3, 0); // 4MHz Oscillator OFF

// Power Menagement in WFI mode

Tmp = 0x0010; // Main Voltage Regulator OFF in WFI

Tmp &= ~PCU_LPRWFI_Mask; // Low Power Regulator ON in Wait-For-Interrupt mode.

Tmp |= 0x0200; // Flash low-power (low-speed) mode select

// Tmp |= 0x0040; // Activate Powerdown Mode

PCU->PWRCTRL |= PCU_WREN_Mask;

PCU->PWRCTRL |= Tmp;

while (PCU->PWRCTRL & 0x4000);

/*==============================*/

// Enter WFI Mode

RCCU->SYSMODE &= ~0x0001;

/*==============================*/

}

Can someon help me ?

Thanks

smart

:-[

Posted on June 24, 2005 at 15:23

Hi Smart,

Your suspend routine seems correct, but I don't think that the high power consumption is due to the MVR.

To have lower power consumption , you have to power down the FLASH during LPWFI mode.

To do this you have to add this instruction:

FLASHR->CR0 |= 0x8000; // set bit PWD

But to do this you must map the interrupt vectors and interrupt service routines in RAM (and remap it to 0x00h). You have to insert a 20µs software delay in the interrupt service routine before accessing any Flash location.

Refer to the STR7x flash reference manual.

Hope it helps

Ciao!

8-)

Posted on July 12, 2005 at 06:37

Excuse me, Bouha, but I believed that when the micro is in LPWFI mode, Flash is automatically in power down. Isn't so?

Thanks

L.

Posted on July 12, 2005 at 07:36

Hi Lucky74,

The Flash is not automaticaly turned in power down mode when going in LPWFI mode, you have to set PWD bit in the FLASH_CR0 register.

Ciao ;)