NEC mPD780065 Series Preliminary User's Manual page 205

(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 the asynchronous serial interface status register (ASIS0),
a receive error interrupt request (INTSER0) will occur. Receive error interrupts requests are generated before
receiving completion interrupts request (INTSR0). Table 13-4 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 13-4 and Figure 13-9).
The contents of ASIS0 are reset (to "0") when the receive buffer register (RXB0) is read or when the next
data is received (if the next data contains an error, its error flag will be set).
Receive Error
Parity error Parity specified during transmission does not match parity of receive data
Framing error Stop bit was not detected
Overrun error Reception of the next data was completed before data was read from the
receive buffer register
RxD0 (input)
INTSR0
INTSER0
(When framing/overrun error occurs)
INTSER0
(When parity error occurs)
Note If a receive error occurs when ISRM0 bit has been set (1), INTSR0 does not occur.
Cautions 1. The contents of ASIS0 are reset (to "0") when the receive buffer register (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 the receive buffer register (RXB0) 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.
CHAPTER 13 SERIAL INTERFACE (UART0)
Table 13-4. Causes of Receive Errors
Cause
Figure 13-9. Receive Error Timing
START D0
Note
Preliminary User's Manual U13420EJ2V0UM00
D1 D2 D6
ASIS0 Value
04H
02H
01H
D7 Parity STOP
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