Rainbow-electronics ATmega161L Manuale Utente Scaricare il pdf (Pagina 79)

ATmega161(L)

1228C–AVR–08/02

The Baud Rate Generator in

Double UART Speed Mode

Note that the baud rate equation is different from the equation on page 76 when the

UART speed is doubled:

• BAUD = Baud rate

• f

= Crystal Clock frequency

• UBR = Contents of the UBRRHI and UBRR Registers (0 - 4095)

• Note that this equation is only valid when the UART transmission speed is doubled.

For standard crystal frequencies, the most commonly used baud rates can be generated

by using the UBR settings in Table 24. UBR values that yield an actual baud rate differ-

ing less than 1.5% from the target baud rate are boldface in the table. However, since

the number of samples are reduced and the system clock might have some variance

(this applies especially when using resonators), it is recommended that the baud rate

error be less than 0.5%.

BAUD

8(UBR 1 )+

------------------------------=

1 2 ... 74 75 76 77 78 79 80 81 82 83 84 ... 158 159

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Rainbow-electronics ATmega161L Manuale Utente Pagina 79