CHAPTER 10 SERIAL INTERFACE FUNCTION
User’s Manual U14492EJ3V0UD
421
(2) Asynchronous serial interface status register 0 (ASIS0)
The ASIS0 register, which consists of 3-bit error flags (PE, FE, and OVE), indicates the error status when
UART0 reception is completed.
The status flag, which indicates a reception error, always indicates the status of the error that occurred most
recently. That is, if the same error occurred several times before the receive data was read, this flag would
hold only the status of the error that occurred last.
The ASIS0 register is cleared to 00H by a read operation. When a reception error occurs, the reception
buffer register 0 (RXB0) should be read and the error flag should be cleared after the ASIS0 register is read.
This register is read-only in 8-bit units.
Caution
When the UARTCAE0 bit or RXE0 bit of the ASIM0 register is set to 0, or when the ASIS0
register is read, the PE, FE, and OVE bits of the ASIS0 register are cleared (0).
7
6
5
4
3
2
1
0
Address
Initial value
ASIS0
0
0
0
0
0
PE
FE
OVE
FFFFFA03H
00H
Bit Position
Bit Name
Function
2
PE
This is a status flag that indicates a parity error.
0: When the ASIM0 register’s UARTCAE0 and RXE0 bits are both set to 0, or
when the ASIS0 register has been read
1: When reception was completed, the transmit data parity did not match
the parity bit
Caution The operation of the PE bit differs according to the settings of the
PS1 and PS0 bits of the ASIM0 register.
1
FE
This is a status flag that indicates a framing error.
0: When the ASIM0 register’s UARTCAE0 and RXE0 bits are both set to 0, or
when the ASIS0 register has been read
1: When reception was completed, no stop bit was detected
Caution For receive data stop bits, only the first bit is checked regardless
of the stop bit length.
0
OVE
This is a status flag that indicates an overrun error.
0: When the ASIM0 register’s UARTCAE0 and RXE0 bits are both set to 0, or
when the ASIS0 register has been read.
1: UART0 completed the next receive operation before reading the RXB0
receive data.
Caution When an overrun error occurs, the next receive data value is not
written to the RXB0 register and the data is discarded.
Содержание V850E/IA1 mPD703116
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