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Oscillator which can be used for MCP2122?

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Ziko87

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As title I'm interfacing with this part of the microchip. The peculiarity of this component is that it needs to run a clock signal synchronized with the serial data to be sent and that is exactly 16 times the maximum baud rate you want.
To achieve the required I am referring to the following document issued by them:

No. AN946

Here is explained in broad terms how to do in different ways, and finally explains and provides an example of what they say is the best method:
Generate a PWM signal characteristics required by the external component.

So far no problem, what is strange is that in this piece of code works only with the particular values ​​of oscillation of quartz that are not standard ones I use that instead (20.0MHz). The document is not clear what happens if you do not use these crystals .. it undergoes some kind of strange error?

What do you think?

Ps. Sorry for my English. I get better!
 

rhaynes

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Using a straight 20MHz and depending on your required baud rate you could have a baud rate error. That error could be small and insignificant or large enough to data errors. The frequencies listed in the tables are for zero frequency error are derived using integer divisors which the PIC must use. Depending on your baud rate requirements you need to calculate the divisors you would use and see what the error is and if that is acceptable for your application.

Ray
 

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