NEC uPD78P078 - Manual (Page 482)

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CHAPTER 20 SERIAL INTERFACE CHANNEL 2
(e) Receive errors
Three kinds of errors can occur during a receive operation: a parity error, framing error, or overrun error.
If the data reception result error flag is set in the asynchronous serial interface status register (ASIS),
a receive error interrupt request (INTSER) is generated. A receive error interrupt is generated prior to
a receive completion interrupt request (INTSR). Receive error causes are shown in Table 20-7.
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 (see Figures 20-9 and 20-10).
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).
Table 20-7. Receive Error Causes
Receive Errors Cause
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
Figure 20-10. Receive Error Timing
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.
RxD (Input)
INTSR Note
INTSER (when a framing
error or an overrun error
is generated)
INTSER (when a parity
error is generated)
D0 D1 D2 D6 D7
STOP
START
Parity