The order in which the data bits are transmitted and received is defined by MSBF in USARTn_CTRL. When MSBF is cleared, data in a
frame is sent and received with the least significant bit first. When it is set, the most significant bit comes first.
The frame format used by the transmitter can be inverted by setting TXINV in USARTn_CTRL, and the format expected by the receiver
can be inverted by setting RXINV in USARTn_CTRL. These bits affect the entire frame, not only the data bits. An inverted frame has a
low idle state, a high start-bit, inverted data and parity bits, and low stop-bits.
18.3.2.2 Parity Bit Calculation and Handling
When parity bits are enabled, hardware automatically calculates and inserts any parity bits into outgoing frames, and verifies the re-
ceived parity bits in incoming frames. This is true for both asynchronous and synchronous modes, even though it is mostly used in
asynchronous communication. The possible parity modes are defined in
Table 18.5 USART Parity Bits on page 531
. When even pari-
ty is chosen, a parity bit is inserted to make the number of high bits (data + parity) even. If odd parity is chosen, the parity bit makes the
total number of high bits odd.
Table 18.5. USART Parity Bits
PARITY BITS [1:0]
Description
00
No parity bit (Default)
01
Reserved
10
Even parity
11
Odd parity
Reference Manual
USART - Universal Synchronous Asynchronous Receiver/Transmitter
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