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32 KHz crystal for ACLK

Qrul
Prodigy 40 points

Other Parts Discussed in Thread: MSP430F2274

Hi,

I'm using EZ430-RF2480 development kit a and I'm trying to create some simple application, which is going to measure real time. My problem is, that I'm using VLO like clock source for ACLK, but I wanted it more accurate. On the target board are two crystals - one is on the side, where MSP430F2274 is - 32,768KHz and one is on the CC2480's side - 32,000 KHz. My idea is, that I use the 32,768KHz crystal like a source for ACLK and it will be source for TimerA. This is my code:

TACTL &= ~MC_1;

BCSCTL1 |= DIVA_3;

BCSCTL3 |= LFXT1S_0;

TACCR0_INIT = 4096;

TACTL = TASSEL_1 + MC_1;

TACCR0 = TACCR0_INIT;

TACCTL0 = CCIE;

TACTL |= MC_1;

But it doesn't work, the LFXT1OF bit is always set and the Timer can't count. Can anybody help me?

I can also use DCO like clock source, but I don't exactly understand, what it is. Is it crystal too or something like VLO?

I didn't find answers for these questions, so I hope, that I'm not asking for nonsense. Thanks!

 

  • 0
    TI__Genius 16215 points

    Hi,

    If you look at the schematic for the eZ430-RF2480 kit, you will see that the 32kHz crystal is not connected to the MSP430. It is actually connected to the cc2480 itself. Looking at the schematic too, the SRDY line is tied to XIN of the MSP430. Hence, this SRDY is already used for different functionality and won't be able to be used to source clock into the MSP430.

    Regards,

    William

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