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about the 32khz osc of LPC1830

Question asked by zhu bin on Jul 30, 2017
Latest reply on Aug 2, 2017 by zhu bin

Hello friends,

   I want to use the alarm timer to wake up from Deep-Sleep(LPC1830) . According to DataSheet,the Alarmtimer is connected directly to the 32kHz OSC. So my question is  whether the 32kHz is external clock or internal clock? If it is a external clock should i connected a 32.768kHz Crystal oscillator to RTCX1/RTCX2 ?

 

I initialize the alarm timer like this:

LPC_CREG->CREG0 &= ~((1 << 3) | (1 << 2));
LPC_CREG->CREG0 |= (1 << 1) | (1 << 0);

LPC_ATIMER->DOWNCOUNTER = 2048;
LPC_ATIMER->PRESET = 1024;

 

but the DOWNCOUNTER  doesn't count ·······

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