Receive Error Timing; Receive Error Causes - NEC PD78056F User Manual

(e) Receive errors
Three kinds of errors can occur during a receive operation: a parity error, framing error, or overrun error.
The data reception result error flag is set in the asynchronous serial interface status register (ASIS) and
at the same time a receive error interrupt request (INTSER) is generated. Receive error causes are shown
in Table 19-7.
It is possible to determine what kind of error was generated during reception by reading the contents of
ASIS in the reception error interrupt servicing (INTSER) (see Figures 19-9 and 19-10).
The contents of ASIS are reset (0) by reading the receive buffer register (RXB) or receiving the next data
(if there is an error in the next data, the corresponding error flag is set).
Receive Errors
Parity error Transmission-time parity specification and reception data parity do not match
Framing error Stop bit not detected
Overrun error Reception of next data is completed before data is read from receive register buffer
RxD (Input)
Note
INTSR
INTSER (when a framing
error or an overrun error
is generated)
INTSER (when a parity
error is generated)
Note If a receive error is generated while bit 1 (ISRM) of the asynchronous serial interface mode register
(ASIM) is set to (1), INTSR is not generated.
Cautions 1. The contents of the asynchronous serial interface status register (ASIS) are reset (0) by
reading the receive buffer register (RXB) or receiving the next data. To ascertain the error
contents, ASIS must be read before reading RXB.
2. The receive buffer register (RXB) must be read even if a receive error is generated. If RXB
is not read, an overrun error will be generated when the next data is received, and the
receive error state will continue indefinitely.
CHAPTER 19 SERIAL INTERFACE CHANNEL 2
Table 19-7. Receive Error Causes
Figure 19-10. Receive Error Timing
D0 D1 D2
START
Cause
D6 D7 Parity
STOP
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