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CHAPTER 16 ASYNCHRONOUS SERIAL INTERFACE (UART)
User’s Manual U16890EJ1V0UD
443
(2) Asynchronous serial interface status register n (ASISn)
The ASISn register, which consists of 3 error flag bits (PEn, FEn and OVEn), indicates the error status when
UARTn reception is complete.
The ASISn register is cleared to 00H by a read operation. When a reception error occurs, the RXBn register
should be read and the error flag should be cleared after the ASISn register is read.
This register is read-only, in 8-bit units.
After reset, ASISn is set to 00H.
Cautions 1. When the ASIMn.UARTEn bit or ASIMn.RXEn bit is cleared to 0, or when the ASISn
register is read, the PEn, FEn, and OVEn bits are cleared (0).
2. Operation using a bit manipulation instruction is prohibited.
3. When the main clock is stopped and the CPU is operating on the subclock, do not
access the ASISn register using an access method that causes a wait.
For details, refer to 3.4.8 (2).
7
0
ASISn
(n = 0, 1)
6
0
5
0
4
0
3
0
2
PEn
1
FEn
0
OVEn
After reset: 00H R Address: ASIS0 FFFFFA03H, ASIS1 FFFFFA13H
PEn
Status flag indicating a parity error
0
When the UARTEn or RXEn bit is cleared to 0, or after the ASISn register has been read
1
When reception was completed, the receive data parity did not match the parity bit
The operation of the PEn bit differs according to the settings of the ASIMn.PSn1 and ASIMn.PSn0 bits.
FEn
Status flag indicating framing error
0
When the UARTEn or RXEn bit is cleared to 0, or after the ASISn register has been read
1
When reception was completed, no stop bit was detected
For receive data stop bits, only the first bit is checked regardless of the stop bit length.
OVEn
Status flag indicating an overrun error
0
When the UARTEn or RXEn bit is cleared to 0, or after the ASISn register has been read.
1
UARTn completed the next receive operation before reading receive data of the RXBn register.
When an overrun error occurs, the next receive data value is not written to the RXBn register and the data is
discarded.