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Discussion Groups | 68HC12 | What Is My Exact P(E)CLOCK? DG256.
Join our technical discussions about Freescale Microcontrollers: M68HC12. (Freescale Semiconductor is a Subsidiary of Motorola).
What Is My Exact P(E)CLOCK? DG256. - jmey...@emittechnologies.com - Mar 13 17:15:47 2009
I'm rocking a Freescale MC9S12DG256B with a crystal oscillator of 16MHz.
What is my exact P CLOCK or E CLOCK supposed to be? I assume it's 8MHz, but my clock algorith is off one second for every minute. I need an accuracy of on minute per day. Is it more like 8.192 MHz?
Please help.
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What is my exact P CLOCK or E CLOCK supposed to be? I assume it's 8MHz, but my clock algorith is off one second for every minute. I need an accuracy of on minute per day. Is it more like 8.192 MHz?
Please help.
------------------------------------
______________________________
Stellaris® MCU Family: New Parts, New Package, New Price.
(You need to be a member of 68hc12 -- send a blank email to 68hc12-subscribe@yahoogroups.com )
Re: What Is My Exact P(E)CLOCK? DG256. - barry callahan - Mar 14 10:16:24 2009
--- In 6...@yahoogroups.com, jmeyer@... wrote:
>
> I'm rocking a Freescale MC9S12DG256B with a crystal oscillator of 16MHz.
>
> What is my exact P CLOCK or E CLOCK supposed to be? I assume it's 8MHz, but my clock algorith is off one second for every minute. I need an accuracy of on minute per day. Is it more like 8.192 MHz?
>
> Please help.
>
Your P Clock and E Clock will be exactly 1/(2^n) of the frequency of your system oscillator. The value of n will vary depending on what you set the related configuration registers to. If your system oscillator is exactly 16.000MHz and your P Clock is "about" 8 MHz, then it should be *exactly* 8.000 MHz.
If your algorithm is giving you bad results, either you're not using a 16.000 MHz crystal, or your algorithm is bad.
I'd suggest getting familiar with the
------------------------------------
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>
> I'm rocking a Freescale MC9S12DG256B with a crystal oscillator of 16MHz.
>
> What is my exact P CLOCK or E CLOCK supposed to be? I assume it's 8MHz, but my clock algorith is off one second for every minute. I need an accuracy of on minute per day. Is it more like 8.192 MHz?
>
> Please help.
>
Your P Clock and E Clock will be exactly 1/(2^n) of the frequency of your system oscillator. The value of n will vary depending on what you set the related configuration registers to. If your system oscillator is exactly 16.000MHz and your P Clock is "about" 8 MHz, then it should be *exactly* 8.000 MHz.
If your algorithm is giving you bad results, either you're not using a 16.000 MHz crystal, or your algorithm is bad.
I'd suggest getting familiar with the
------------------------------------
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