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CHAPTER 11 SERIAL INTERFACE
148
(e) Receive errors
The following three errors may occur during a receive operation: a parity error, framing error, or
overrun error. If the error flag in asynchronous serial interface status register 00 (ASIS00) is set to 1 as
a result of data reception, a reception error interrupt request (INTSER00) is generated. The reception
error interrupt occurs before the reception completion interrupt request (INTSR00). Receive error
causes are shown in Table 11-4.
It is possible to determine what kind of error was generated during reception by reading the contents of
ASIS00 in the reception error interrupt servicing (INTSER00) (see Table 11-4 and Figure11-9).
The contents of ASIS00 are cleared to 0 by reading reception buffer register 00 (RXB00) or receiving
the next data (if there is an error in the next data, the corresponding error flag is set).
Table 11-4. Receive Error Causes
Receive Errors
Cause
ASIS00 Value
Parity error
Transmission-time parity specification and reception data parity do not match
04H
Framing error
Stop bit not detected
02H
Overrun error
Reception of next data is completed before data is read from reception buffer
register 00
01H
Figure 11-9. Receive Error Timing
Note
If the receive error is generated when the ISRM00 bit is set to 1, INTSR00 is not generated.
Cautions 1. The contents of asynchronous serial interface status register 00 (ASIS00) are
cleared to 0 by reading reception buffer register 00 (RXB00) or receiving the next
data. To ascertain the error contents, read ASIS00 before reading RXB00.
2. Be sure to read reception buffer register 00 (RXB00) even if a receive error is
generated. If RXB00 is not read, an overrun error will be generated when the next
data is received, and the receive error state will continue indefinitely.
STOP
D7
D6
D2
D1
D0
START
RxD00 (Input)
(Parity error generated)
INTSR00
Note
(Framing error or overrun
error generated)
INTSER00
INTSER00
Parity