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CHAPTER 11 SERIAL INTERFACE FUNCTION
User’s Manual U15109EJ3V0UD
452
(e) Receive error
There are three types of error during a receive operation: parity errors, framing errors, and overrun errors.
When, as the result of data reception, an error flag is set in asynchronous serial interface status register n
(ASISn).
By reading the contents of ASISn during receive completion interrupt servicing (INTSRn), it is possible to
detect which error has occurred at reception.
The contents of ASISn are reset (0) by reading receive buffer register n (RXBn) or receiving subsequent data
(if there is an error in the subsequent data, the error flag is set).
Table 11-14. Receive Error Causes
Receive Error
Cause
ASISn Value
Parity error
Parity specification at transmission and receive data parity do not match.
04H
Framing error
Stop bit is not detected.
02H
Overrun error
Reception of subsequent data was completed before data was read from the
receive buffer register.
01H
Figure 11-52. Receive Error Timing
RxDn (input)
INTSRn
Note
D7
D6
D2
D1
D0
Parity
STOP
START
Note
Even if a receive error occurs when the ISRMn bit of ASIMn is set (1), INTSRn is not generated.
The receive error type can be ascertained by reading the contents of ASISn in the reception
completion interrupt servicing (INTSRn).
Cautions 1. The contents of asynchronous serial interface status register n (ASISn) are reset (0) by
reading receive buffer register n (RXBn) or receiving subsequent data. To check the
contents of an error, always read ASISn before reading RXBn.
2. Be sure to read receive buffer register n (RXBn) even when a receive error has
occurred. If RXBn is not read out, an overrun error will occur during subsequent data
reception and as a result receive errors will continue to occur.
Remark
n = 0 to 3