Internal oscillation should not be relied on for
accuracy. In one AVR example, it used a 32,768 crystal
to tune the main clock. When I ramp up to a higher
baud, I got garbage. In the document it claims that it
can improve accuracy and reduce error for a given baud
rate when certain clock osc is being used. You may
want to look at AVR ATmega 169P for some clue. The
subtitle should be "Examples of baud rate settings".

John

PS: Tuning it may be a hassle........



--- Xiaofan Chen <xiaofanc@gmail.com> wrote:

> Sometimes we need to exchange data between two MCUs
> through opto
> coupler (or magnetic coupler from Analog Device). If
> both side have SPI or
> I2C or UART, then we will normally use these
> resources. However we may
> not have these features (or they have better things
> to do), then we might
> think of using  two port pins for serial
> communication(software UART).
> 
> Here is once question, if we need relative high
> speed, say to transmit
> 8 bytes of data (64bits) continuously per 1ms
> (>=64kbps). We might also
> need to use certain encoding method so that it is
> more immune to noise. Is
> this easily doable with small MCUs like small
> PIC16Fs running the internal
> RC oscillator of 8MHz or 4-clock-per-instruction
> 8051s running at 20MHz
> crystal? Is it easily doable with an MSP430 with
> internal calibrated 16Mhz
> oscillator (single clock per instruction but clock
> tolerance is +/-5% over
> all temperature)? Will this kind of serial
> communication make the MCU
> fully occupied?
> 
> Regards,
> Xiaofan
> -- 
> http://www.piclist.com PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist
> 


__________________________________________________
Do You Yahoo!?
Tired of spam?  Yahoo! Mail has the best spam protection around 
http://mail.yahoo.com 
-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist