Receive Error Causes; Receive Error Timing - NEC PD78081(A) User Manual

(e) Receive errors
Three kinds of errors can occur during a receive operation: a parity error, framing error, or overrun error.
When a data reception results error flag is set in the asynchronous serial interface register (ASIS), a
reception error interrupt request (INTSER) is generated.
The reception error interrupt request is generated first before the reception completed interrupt request
(INTSR). Receive error causes are shown in Table 11-7.
It is possible to determine what kind of error was generated during reception by reading the contents of
the asynchronous serial interface status register (ASIS) in the reception error interrupt servicing (INTSER)
(see Figures 11-9 and 11-10).
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)
INTSR
INTSER
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 11 SERIAL INTERFACE CHANNEL 2
Table 11-7. Receive Error Causes
Figure 11-10. Receive Error Timing
D0 D1 D2
START
Cause
D6 D7 Parity
STOP
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