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CHAPTER 16 SERIAL INTERFACE UART0
User’s Manual U15798EJ2V0UD
(e) Receive errors
Three types of errors can occur during a receive operation: parity error, framing error, or overrun error. If,
as the result of data reception, an error flag is set to asynchronous serial interface status register 0 (ASIS0),
a receive error interrupt request (INTSER0) will occur. Receive error interrupt requests are generated before
receive completion interrupt requests (INTSR0). Table 16-4 lists the causes behind receive errors.
As part of receive error interrupt request (INTSER0) servicing, the contents of ASIS0 can be read to determine
which type of error occurred during the receive operation (see
Table 16-4
and
Figure 16-10
).
The contents of ASIS0 are reset (to “0”) when receive buffer register 0 (RXB0) is read or when the next data
is received (if the next data contains an error, its error flag will be set).
Table 16-4. Causes of Receive Errors
Receive Error
Cause
ASIS0 Value
Parity error
Specified parity does not match parity of receive data
04H
Framing error
Stop bit was not detected
02H
Overrun error
Reception of the next data was completed before data was read from
01H
receive buffer register 0 (RXB0)
Figure 16-10. Receive Error Timing
RxD0 (input)
D0
D1
D2
D6
D7
Parity
STOP
START
INTSR0
Note
INTSER0
(When framing/overrun error occurs)
INTSER0
(When parity error occurs)
Note
Even if a receive error occurs when the ISRM0 bit has been set (1), INTSR0 does not occur.
Cautions 1. The contents of asynchronous serial interface status register 0 (ASIS0) are reset (to
“0”) when receive buffer register 0 (RXB0) is read or when the next data is received.
To obtain information about the error, be sure to read the contents of ASIS0 before
reading RXB0.
2. Be sure to read the contents of receive buffer register 0 (RXB0) after a receive
completion interrupt request is generated even when a receive error has occurred.
Overrun errors will occur during the next data receive operations and the receive error
status will remain until the contents of RXB0 are read after a receive completion
interrupt request is generated.
