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CHAPTER 19 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.
The data reception result error flag is set in the asynchronous serial interface status register (ASIS) and
a receive error interrupt request (INTSER) is generated. The receive error interrupt is generated faster
than receive completion interrupt (INTSR). 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 (see
Figures 19-10
and
19-11
).
The contents of ASIS are reset (to 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 19-7. 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 19-11. Receive Error Timing
Note
INTSR is not generated if a receive error is generated while bit 1 (ISRM) of the asynchronous serial
interface mode register (ASIM) is set (to 1).
Cautions 1. The contents of the asynchronous serial interface status register (ASIS) are reset (to
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.
Parity
STOP
D7
D6
D2
D1
D0
R
X
D (Input)
INTSR
Note
INTSER (When framing/
overrun error occurs)
INTSER (When parity
error occurs)
START