CHAPTER 10 SERIAL INTERFACE FUNCTION
User’s Manual U13850EJ6V0UD
417
(e) Receive error
Three types of errors can occur during a receive operation: a parity error, framing error, and overrun error.
When, as the result of data reception, an error flag is set in asynchronous serial interface status register n
(ASISn), the receive error interrupt request (INTSERn) is generated. The receive error interrupt request is
generated prior to the receive completion interrupt request (INTSRn).
By reading the contents of ASISn during receive error interrupt servicing (INTSERn), it is possible to
ascertain which error has occurred during 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 10-17. 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 10-54. Receive Error Timing
RxDn (Input)
INTSRn
Note
D7
D6
D2
D1
D0
Parity
STOP
START
INTSERn
INTSERn
(When parity error occurs)
Note
Even if a receive error occurs when the ISRMn bit of ASIMn is set (1), INTSRn is not generated.
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 error, always read ASISn before reading RXBn.
2.
Be sure to read receive buffer register n (RXBn) even when a receive error occurs. 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, 1
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