IBM uPD78082 - Manual (Page 184)

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CHAPTER 11 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.
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).
Table 11-7. 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 11-10. Receive Error Timing
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.
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D1 D2 D6 D7 Parity D0 RxD (Input)
INTSR
STOP
START
INTSER
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