Nearly all of the PIC data sheets on parts with built in UARTS have that
particular section of the table messed up. The rest of the boxes are correct,
just that one is wrong. IIRC, you just need to shift all the values of one
column up or down and it matches up. I assume Mchip knows about it, but whoever
does their docs simply copies the data sheet from the closest PIC and then
modifies it.
That could be why the 16c54 data sheet is still a 'preliminary document'.
I use the equations all the time, anyway. They are easier to remember than the
tables ;-).
BRGH = high(1)
BPS = Fosc/(16 * (spbrg + 1) )
spbrg = 1 + Fosc/(16 * BPS)
For BRGH = low (0) use 64 in place of 16 in both above equations.
These equations are used for every built in USART Microchip has offered so far,
with the only caveat that the 18C chips have a PLL; I believe that Fosc in the
above equations refers to the frequency AFTER the PLL, not the
crystal/resonator/RC/clock input frequency.
-Adam
D Lloyd wrote:
{Quote hidden}>
> Hi,
>
> With respect to this data sheet, have I missed the blindingly obvious or do I
> take it that the baud rate figures are incorrect for the 4MHz clock source ?
> (page 156, table 15-5 "BAUD RATES FOR ASYNCHRONOUS MODE (BRGH = 1)").
> I checked the MCHIP site for errata documents but none pertain to this. If there
> is a correction, anyone know what/where it is?
>
> Regards,
>
> Dan
>
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