34.2.2.5 Receive Framing Error

Each character in the receive FIFO buffer has a corresponding Framing Error Flag bit. A framing error indicates that the Stop bit was not seen at the expected time. For example, a Break condition will be received as a 0x00 byte with the framing error bit set.

The Framing Error flag is accessed via the FERIF bit. The FERIF bit represents the frame status of the top unread character of the receive FIFO. Therefore, the FERIF bit must be read before reading UxRXB.

The FERIF bit is read-only and only applies to the top unread character of the receive FIFO. A framing error (FERIF = 1) does not preclude reception of additional characters. It is neither necessary nor possible to clear the FERIF bit directly. Reading the next character from the FIFO buffer will advance the FIFO to the next character and the next corresponding framing error, if any.

The FERIF bit is cleared when the character at the top of the FIFO does not have a framing error or when all bytes in the receive FIFO have been read. Clearing the ON bit resets the receive FIFO, thereby also clearing the FERIF bit.

A framing error will generate a summary UxEIF interrupt when the FERIE bit is set. The summary error is reset when the FERIF bit of the top of the FIFO is ‘0’ or when all FIFO characters have been retrieved.