Hi everyone,

I’m using MSP430F149. I have a 32KHz xtal in LFXT1CTL and no xtal in XT2CTL. I’m already using ACLK (at 32.768KHz) to feed both Timer_A and Timer_B. I want to use my watchdog with a freq lower than 1Hz so I thought I would feed it using SMCLK using LFXT1CLK as source. So I checked the user’s guide and everything looked ok:



“SMCLK: Sub-main clock. SMCLK is software selectable as LFXT1CLK, XT2CLK (if available on-chip), or DCOCLK. SMCLK is divided by 1, 2, 4, or 8. SMCLK is software selectable for individual peripheral modules.”



So I just went on to see how to configure basic clock module registers and read:



“SELS Bit 3 Select SMCLK. This bit selects the SMCLK source.

0 DCOCLK

1 XT2CLK when XT2 oscillator present on-chip. LFXT1CLK when XT2 oscillator not present on-chip.”



So I thought Oscilator != Xtal and even if there’s no xtal in XT2CTL the oscillator must be present on-chip. So I guess it’s not possible. But I just want to check if I’m right.

Is it possible to feed SMCLK using LFXT1CLK in MSP430F149?



Thanks, Jon.



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Hi Jon,

I use the F261x but I think it is the same.
I is NOT possible in the chip (if the XT2-module is present,
nothing to do with the Xtal). There is a Figure (5-1 in my case)
which show that there is only a connection if XT2-module
is absend, otherwise two outputs working agains each other.
But you can use the ACLK pin and connect it to the TX2IN pin.
And than configurethe XT2CLT.
Never tried this, but it should work.

Regards,

Dirk
Jon Garcia de Salazar Bilbao schrieb:
>
>
> Hi everyone,
>
> I’m using MSP430F149. I have a 32KHz xtal in LFXT1CTL and no xtal in
> XT2CTL. I’m already using ACLK (at 32.768KHz) to feed both Timer_A and
> Timer_B. I want to use my watchdog with a freq lower than 1Hz so I
> thought I would feed it using SMCLK using LFXT1CLK as source. So I
> checked the user’s guide and everything looked ok:
>
> “SMCLK: Sub-main clock. SMCLK is software selectable as LFXT1CLK,
> XT2CLK (if available on-chip), or DCOCLK. SMCLK is divided by 1, 2, 4,
> or 8. SMCLK is software selectable for individual peripheral modules.”
>
> So I just went on to see how to configure basic clock module registers
> and read:
>
> “SELS Bit 3 Select SMCLK. This bit selects the SMCLK source.
>
> 0 DCOCLK
>
> 1 XT2CLK when XT2 oscillator present on-chip. LFXT1CLK when XT2
> oscillator not present on-chip.”
>
> So I thought Oscilator != Xtal and even if there’s no xtal in XT2CTL
> the oscillator must be present on-chip. So I guess it’s not possible.
> But I just want to check if I’m right.
>
> Is it possible to feed SMCLK using LFXT1CLK in MSP430F149?
>
> Thanks, Jon.
>
>

--
Ingenieurbüro Dirk Rapp
Hard- & Softwareentwicklung

Adelhauser Str. 36
79585 Steinen

Tel.: +49 7627 923494
Mobil: +49 173 6686246

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No.

--- In m..., "Jon Garcia de Salazar Bilbao" wrote:
>
> Hi everyone,
>
> I’m using MSP430F149. I have a 32KHz xtal in LFXT1CTL and no xtal in XT2CTL. I’m already using ACLK (at 32.768KHz) to feed both Timer_A and Timer_B. I want to use my watchdog with a freq lower than 1Hz so I thought I would feed it using SMCLK using LFXT1CLK as source. So I checked the user’s guide and everything looked ok:
>
>
>
> “SMCLK: Sub-main clock. SMCLK is software selectable as LFXT1CLK, XT2CLK (if available on-chip), or DCOCLK. SMCLK is divided by 1, 2, 4, or 8. SMCLK is software selectable for individual peripheral modules.”
>
>
>
> So I just went on to see how to configure basic clock module registers and read:
>
>
>
> “SELS Bit 3 Select SMCLK. This bit selects the SMCLK source.
>
> 0 DCOCLK
>
> 1 XT2CLK when XT2 oscillator present on-chip. LFXT1CLK when XT2 oscillator not present on-chip.”
>
>
>
> So I thought Oscilator != Xtal and even if there’s no xtal in XT2CTL the oscillator must be present on-chip. So I guess it’s not possible. But I just want to check if I’m right.
>
> Is it possible to feed SMCLK using LFXT1CLK in MSP430F149?
>
>
>
> Thanks, Jon.
>
>
>
>
>
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Thanks guys!!!



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