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CHAPTER 17 ASYNCHRONOUS SERIAL INTERFACE/3-WIRE SERIAL I/O
(e) Receive error
Errors that occur during reception are of three types: parity errors, framing errors, and overrun errors. As
the data reception result error flag is set inside the asynchronous serial interface status register n (ASISn),
the receive error interrupt (INTSERn) is generated. A receive error interruption is generated before a receive
end interrupt (INTSRn). Receive error causes are shown in Table 17-5.
What type of error has occurred during reception can be detected by reading the contents of the asynchronous
serial interface status register n (ASISn) during processing of the receive error interrupt (INTSERn) (rerer
to
Table 17-5
and
Figure 17-10
).
The contents of ASISn are reset to 0 either when the receive buffer register n (RXBn) is read or when the
next data is received (If the next data has an error, this error flag is set).
Remark
n = 1, 2
Table 17-5. Receive Error Causes
Receive Error
Cause
ASIS
Parity error
Parity specified for transmission and parity of receive data don’t match
04H
Framing error
Stop bit was not detected
02H
Overrun error
Next data reception was completed before data was read from the receive buffer register
01H
Figure 17-10. Receive Error Timing
Note
If a receive error occurs, when bit ISRMn is set (1), INTSRn is not generated.
Cautions 1. The contents of the ASISn register are reset to 0 either when the receive buffer
register n (RXBn) is read or when the next data is received. To find out the contents
of the error, be sure to read ASIS before reading RXBn.
2. Be sure to read the receive buffer register n (RXBn) even when a receive error occurs.
If RXBn is not read, an overrun error will occur at reception of the next data, and the
receive error status will continue indefinitely.
Remark
n = 1, 2
D1
D2
D6
D7
Parity
D0
RxDn (input)
INTSRn
Note
STOP
START
INTSERn
(Framing/overrrun
errors occur)
INTSERn
(when parity
errors occur)