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Chapter 13
Serial Interface Function
Preliminary User’s Manual U15839EE1V0UM00
(2)
Asynchronous serial interface status registers (ASIS0 to ASIS2)
The ASISn register, which consists of 3-bit error flags (PE, FE and OVE), indicates the error status
when UART5n 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 ASISn register is cleared to 00H by a read operation. When a reception error occurs, the
reception buffer register (RXBn) should be read and the error flag should be cleared after the
ASISn register is read.
This register is read-only in 8-bit or 1-bit units (n = 0, 1).
Caution:
When the Power bit or RXE bit of the ASIMn register is set to 0, or when the ASIS0
register is read, the PE, FE, and OVE bits of the ASISn register are cleared (0).
Figure 13-3:
Asynchronous Serial Interface Status Registers (ASIS0, ASIS1)
7
6
5
4
3
2
1
0
Address
Initial
value
ASIS0
0
0
0
0
0
PE
FE
OVE
FFFF FA03H
00H
ASIS1
0
0
0
0
0
PE
FE
OVE
FFFF FA43H
00H
Bit Position
Bit Name
Function
2
PE
This is a status flag that indicates a parity error.
0: When the ASIMn register’s Power and RXE bits are both set to 0, or
when the ASISn 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 ASIMn register.
1
FE
This is a status flag that indicates a framing error.
0: When the ASIMn register’s Power and RXE bits are both set to 0, or
when the ASISn 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 number of stop bits.
0
OVE
This is a status flag that indicates an overrun error.
0: When the ASIMn register’s Power and RXE bits are both 0, or when
the ASISn register has been read.
1: UART5n completed the next receive operation before reading the
RXBn receive data.
Caution:
When an overrun error occurs, the next receive data value
is not written to the RXBn register and the data is
discarded.
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