24.3.2.2 Frame Formats

Data transfer is frame based, where a serial frame consists of one character of data bits with synchronization bits (start and stop bits) and an optional parity bit for error checking. This does not apply to master SPI operation (See 24.3.2.2.2 SPI Frame Formats). The USART accepts all combinations of the following as valid frame formats:

  • 1 start bit
  • 5, 6, 7, 8 or 9 data bits
  • no, even, or odd parity bit
  • 1 or 2 stop bits

Figure 24-5 illustrates the possible combinations of frame formats. Bits inside brackets are optional.

Figure 24-5. Frame Formats

St Start bit, always low.

(n) Data bits (0 to 8).

P Parity bit, may be odd or even.

Sp Stop bit, always high.

IDLE No transfer on the communication line (RxD or TxD). The IDLE state is always high.