at91sam9g20-cu ATMEL Corporation, at91sam9g20-cu Datasheet - Page 477

• Manufacturer Part Number: at91sam9g20-cu
• Description: At91 Arm Thumb Microcontrollers
• Manufacturer: ATMEL Corporation

32.6.3.9
6384B–ATARM–15-Dec-08
Parity
The USART supports five parity modes selected by programming the PAR field in the Mode
Register (US_MR). The PAR field also enables the Multidrop mode, see
page
If even parity is selected, the parity generator of the transmitter drives the parity bit at 0 if a num-
ber of 1s in the character data bit is even, and at 1 if the number of 1s is odd. Accordingly, the
receiver parity checker counts the number of received 1s and reports a parity error if the sam-
pled parity bit does not correspond. If odd parity is selected, the parity generator of the
transmitter drives the parity bit at 1 if a number of 1s in the character data bit is even, and at 0 if
the number of 1s is odd. Accordingly, the receiver parity checker counts the number of received
1s and reports a parity error if the sampled parity bit does not correspond. If the mark parity is
used, the parity generator of the transmitter drives the parity bit at 1 for all characters. The
receiver parity checker reports an error if the parity bit is sampled at 0. If the space parity is
used, the parity generator of the transmitter drives the parity bit at 0 for all characters. The
receiver parity checker reports an error if the parity bit is sampled at 1. If parity is disabled, the
transmitter does not generate any parity bit and the receiver does not report any parity error.
Table 32-6
depending on the configuration of the USART. Because there are two bits at 1, 1 bit is added
when a parity is odd, or 0 is added when a parity is even.
Table 32-6.
When the receiver detects a parity error, it sets the PARE (Parity Error) bit in the Channel Status
Register (US_CSR). The PARE bit can be cleared by writing the Control Register (US_CR) with
the RSTSTA bit at 1.
Character
478. Even and odd parity bit generation and error detection are supported.
A
A
A
A
A
shows an example of the parity bit for the character 0x41 (character ASCII “A”)
Parity Bit Examples
Figure 32-22
Hexa
0x41
0x41
0x41
0x41
0x41
illustrates the parity bit status setting and clearing.
0100 0001
0100 0001
0100 0001
0100 0001
0100 0001
AT91SAM9G20 Preliminary
Binary
Parity Bit
None
1
0
1
0
“Multidrop Mode” on
Parity Mode
Space
None
Even
Mark
Odd
477