Hi Zhengsu ,
I suggest you read the the documentation for your device and
have an extra look into the "Basic Clock and Timing" Appnote from
TI.
Greetz,
Georg
Zhengsu Gao wrote:
>
>> if you don't need an accurate clock in the "fast" phase, you could use
>> DCOCLK at it max values for MCLK. this means that the CPU runs at about
>> 5MHz. this frequency won't be temperature stable and is somewhat lower
>> than your 8MHz.
>
> If I want system runs in 8MHz, I use a 8MHz crystal at XT2, what's the
> difference with your suggestion?
>
>>
>> you may be able to use a watch crystal (32768Hz) at XT1. it can be used
>> for the Timer_A (and maybe Watchdog) module. this way you'd have a
>> accurate time and still a fast CPU.
>
> Can you explain detail about this way? You mean use a watch crystal
> at XT1, CPU will have an accurate time and fast enough?
>
>
> Thank you very much
>
> regards
> Zhengsu
>
>>> However, if I use on 8 MHz crystal, while di
>>> ----- Original Message ----- From: "Chris Liechti" <[email protected]>
>>> To: <[email protected]>
>>> Sent: Friday, December 03, 2004 5:05 PM
>>> Subject: Re: [Mspgcc-users] About system fequency
>>>
>>>
>>>> Gao Zhengsu wrote:
>>>>
>>>>> Hi, everybody:
>>>>> I have a question about system frequency. When I use an 8 MHz
>>>>> crystal in
>>>>> XT2, can I change system frequency from 8MHz to 1MHz simply by
>>>>> divider at run
>>>>> time without losing anything.
>>>>
>>>>
>>>>
>>>> basicaly yes, div 8 is the highest divider you can select in the basic
>>>> clock module and you can switch it at runtime.
>>>> switching clocks can be tricky in some cases, e.g. if you want to
>>>> have a
>>>> realtime clock running accurately.
>>>>
>>>> it's not the same as connecting a lower frequency crystal. in general
>>>> faster clocks use more current. so using a faster crystal than you need
>>>> means less battery life.
>>>>
>>>> chris
>>>>
>>>>
>>>> -------------------------------------------------------
