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Necessity of crystal oscillator for a controller

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Sajjadkhan

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I know a controller internal oscillator like in PIC is composed of RC oscillator and its frequency drifts as temperature drifts. so in UART communication we need to have an external oscillator, but is it also true in the case of SPI or I2C communication?
 

sequel

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it all depends on the error rate that your design can accommodate....large frequency drift may introduce framing error which will certainly report false data to the system
 

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PIC RC oscillator accuracy is often sufficient for UARToperation (depends on the temperature range and PIC type). I don't see a reason why it shouldn't work for SPI and I2C.
 

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Both SPI and I2C are synchronous interfaces that utilize separate data and clock lines where the bit-data is sampled by the receiver relative to an edge of the clock signal. Therefore, the data rate does not have to be at a specific frequency - although devices will impose upper and lower frequency limits. Even if the RC oscillator in the PIC exhibits significant drift it should be well within the frequency range of any SPI or I2C device.
 

Sajjadkhan

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Both SPI and I2C are synchronous interfaces that utilize separate data and clock lines where the bit-data is sampled by the receiver relative to an edge of the clock signal. Therefore, the data rate does not have to be at a specific frequency - although devices will impose upper and lower frequency limits. Even if the RC oscillator in the PIC exhibits significant drift it should be well within the frequency range of any SPI or I2C device.
make sense :)
 

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