25.3.2.2 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 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 25-5 illustrates the possible combinations of frame formats. Bits inside brackets are optional.
| Symbol | Meaning |
|---|---|
| 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 |