
CHAPTER 10
SERIAL INTERFACE FUNCTION
User’s Manual U12768EJ4V1UD
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(v) 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). Table 10-9 shows receive error causes.
By reading the contents of ASISn during receive error interrupt servicing (INTSERn), it is possible to ascertain
which error has occurred during reception (see Table 10-9 and 10.4.2 (2) Asynchronous serial interface
status registers 0 and 1 (ASIS0, ASIS1)
The contents of ASISn are reset (0) by reading the receive buffer register (RXBn) or receiving subsequent
data (if there is an error in the subsequent data, the error flag is set).
Table 10-9. 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 10-34. Receive Error Timing
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 an 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
START
D0
RxDn (Input)
INTSRnNote
INTSERn
(When parity error occurs)
D1
D2
D6
D7
STOP
Parity