LPC43xx Deep power down wakeup after more than 64seconds

[KhaVo]

Hi all,

As LPCOpen sample pmc_states.c,

        Chip_ATIMER_DeInit(LPC_ATIMER);
        ATIMER_ClearInts();
        Chip_ATIMER_Init(LPC_ATIMER, RTC_ALARM_TIME*1000);
        LPC_ATIMER->DOWNCOUNTER = RTC_ALARM_TIME*1000;
        Chip_ATIMER_IntEnable(LPC_ATIMER);
                
        /* Call Pre SleepPowerDown function */
        PMC_Pre_SleepPowerDown();

        /* Goto Deep Sleep mode */
        Chip_PMC_Set_PwrState(Pwr_state);

MCU will wake-up by ATimer, but this is Timer 16bit and runs at 1024Hz clock, so the maximum time is 64 second.

1. How could sleep more than that?
2. Is RTC wake-up really work? If it is, why we need to config the ATimer?

Thanks in advance!

Regards,
Kha Vo

[KhaVo]

Hi jeremyzhou,

Thanks for your answers!

So to sleep longer, I need to use RTC wake up. I face another problem with RTC initializing that it take 2 second to init RTC each booting. I've posted this issue here.

Hoping that you or others could help!

Thanks,

Kha Vo

[jeremyzhou]

Hi Kha Vo,

1. How could sleep more than that?

The maximum period is 64s, as the counter/timer clock is fixed :1024 Hz.

2. Is RTC wake-up really work? If it is, why we need to config the ATimer?

In my opinion, the Atimer is particular to generate periodic interrupt which can be used to wake up the device from a low power mode, however the RTC is more complicated than it.
Have a great day,
Ping

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