Necessity of crystal oscillator for a controller

Status
Not open for further replies.

Sajjadkhan

Full Member level 5
Joined
Sep 25, 2010
Messages
307
Helped
17
Reputation
34
Reaction score
16
Trophy points
1,298
Location
Rawalpindi,Pakistan
www.facebook.com
Activity points
4,199
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?
 

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
 

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.
 

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
 

Status
Not open for further replies.

Similar threads

Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…