
CHAPTER 15 ASYNCHRONOUS SERIAL INTERFACE (UART)
User
’
s Manual U15862EJ3V0UD
448
(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 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, reception buffer
register n (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 units.
Cautions 1. When the UARTEn bit or RXEn bit of the ASIMn register is set to 0, or when the ASISn
register is read, the PEn, FEn, and OVEn bits of the ASISn register are cleared (0).
2. Operation using a bit manipulation instruction is prohibited.
7
0
ASISn
6
0
5
0
4
0
3
0
2
PEn
1
FEn
0
OVEn
After reset: 00H R Address: FFFFFA03H, FFFFFA13H, FFFFFA23H
PEn
Status flag indicating a parity error
0
When the ASIMn register
’
s UARTEn or RXEn bit is set 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 PSn1 and PSn0 bits of the ASIMn register.
FEn
Status flag indicating framing error
0
When the ASIMn register
’
s UARTEn or RXEn bit is set 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 ASIMn register
’
s UARTEn or RXEn bit is set to 0, or after the ASISn register has been read.
1
UARTn completed the next receive operation before reading the RXBn receive data.
When an overrun error occurs, the next receive data value is not written to the RXBn register and the data is
discarded.
Remark
n = 0, 1 (V850ES/KF1, V850ES/KG1)
n = 0 to 2 (V850ES/KJ1)