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CHAPTER 8 SERIAL INTERFACE FUNCTION
(2) Asynchronous serial interface status registers 0 and 1 (ASIS0, ASIS1)
These registers consist of the 3-bit error flag that indicates error status when UARTn receive is completed
and the transmit status flag.
The error flags always indicate the status of an error that has occurred most recently. If two or more errors
occur before the current received data, only the status of the error that has occurred last is retained.
If a receive error occurs, read the receive buffer RXBn after reading the ASISn registers, and then clear the
error flag.
These registers can only be read in 8- or 1-bit units.
Bit Position
Bit Name
Function
7
SOTn
Status Of Transmission
Status flag that indicates transmission operation status.
Set (1)
: Beginning of transmission of a data frame (writing to TXSn register)
Clear (0) : End of transmission of a data frame (occurrence of INTSTn interrupt)
When serial data transfer begins, this flag will indicate if the transmit shift register is ready to be
written or not.
2
PEn
Parity Error
Status flag that indicates parity error.
Set (1)
: Transmit parity and receive parity do not match
Clear (0) : Processing to read out the data from the receive buffer.
1
FEn
Framing Error
Status flag that indicates framing error.
Set (1)
: Stop bit is not detected
Clear (0) : Processing to read out the data from the receive buffer.
0
OVEn
Overrun Error
Status flag that indicates overrun error.
Set (1)
: Set when UARTn has completed the next receive processing before obtaining the
receive data from the receive buffer.
Clear (0) : Processing to read out the receive data from the receive buffer.
Because contents of receive shift register are transferred to receive buffer each time one frame
of data has been received, if overrun error occurs, next receive data is written over contents of
receive buffer, and previous receive data is discarded.
Remark
n = 0, 1
Address
FFFFF0C4H
7
SOT0
ASIS0
6
0
5
0
4
0
3
0
2
PE0
1
FE0
0
OVE0
After reset
00H
FFFFF0D4H
SOT1
ASIS1
0
0
0
0
PE1
FE1
OVE1
00H