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ST72F264

shermantec
Associate II
Posted on July 15, 2005 at 04:59

ST72F264

3 REPLIES 3
shermantec
Associate II
Posted on July 10, 2005 at 11:11

I would like to use the internal RC oscillator and also use SCI communication @4800baud.

I couldn't find in the datasheet the absolute min/max RC clock deviation between ST72264 devices.

I would like to know if it's safe to use the internal RC without preforming calibration for each device? (the other timing beside the SCI communication is negligible).

Thx

torrey
Associate II
Posted on July 14, 2005 at 13:07

In section 6.2 (Multi-Oscillator) of the datasheet, it indicates that the RC oscillator has lower frequency accuracy.

In section 13.5.4 (RC Oscillators), it indicates that the internal frequency can vary from 2 to 6 MHz. Since this is a factor of 3 difference, I'm not sure if there is much hope for any SCI communication without calibration through the Baud Rate registers and/or Extended Prescalers.

It also looks like temperature can affect RC timing significantly, so you may want to make sure you are at operating temp before attempting calibration.

fggnrc
Associate II
Posted on July 15, 2005 at 04:59

Latino,

even if ST72264 devices SCI are not LIN compatible, you could follow what LIN protocol suggests to syncronize clocks.

For instance, the sender may send a BREAK character whose duration is known. The ST2264 receiver could then measure this duration and set-up his local oscillator according to the result.

Then, the only thing that matters is the clock short-term stability.

I hope I was useful...

EtaPhi