Datasheet

145
2503Q–AVR–02/11
ATmega32(L)
The USART Character SiZe (UCSZ2:0) bits select the number of data bits in the frame. The
USART Parity mode (UPM1:0) bits enable and set the type of parity bit. The selection between
one or two stop bits is done by the USART Stop Bit Select (USBS) bit. The receiver ignores the
second stop bit. An FE (Frame Error) will therefore only be detected in the cases where the first
stop bit is zero.
Parity Bit Calculation The parity bit is calculated by doing an exclusive-or of all the data bits. If odd parity is used, the
result of the exclusive or is inverted. The relation between the parity bit and data bits is as
follows::
P
even
Parity bit using even parity
P
odd
Parity bit using odd parity
d
n
Data bit n of the character
If used, the parity bit is located between the last data bit and first stop bit of a serial frame.
P
even
d
n 1–
… d
3
d
2
d
1
d
0
0
P
odd
⊕⊕⊕⊕⊕⊕
d
n 1–
… d
3
d
2
d
1
d
0
1⊕⊕⊕⊕⊕⊕
=
=