CHAPTER 12 SERIAL INTERFACE 20
(3) Asynchronous serial interface status register 20 (ASIS20)
ASIS20 indicates the type of a reception error, if it occurs while asynchronous serial interface mode is set.
ASIS20 is set with a 1-bit or 8-bit memory manipulation instruction.
The contents of ASIS20 are undefined in 3-wire serial I/O mode.
RESET input sets ASIS20 to 00H.
Figure 12-5. Format of Asynchronous Serial Interface Status Register 20
Symbol
ASIS20
7
0
6
0
5
0
4
0
3
0
<2> <1> <0>
Address
FF71H
After reset
00H
R/W
R
PE20 FE20 OVE20
PE20
Parity error flag
0
1
No parity error has occurred.
A parity error has occurred (when the parity of transmit data does not match).
FE20
Flaming error flag
No framing error has occurred.
0
1
A framing error has occurred (when stop bit is not detected).Note 1
OVE20
Overrun error flag
No overrun error has occurred.
0
1
An overrun error has occurred.Note 2
(when the next receive operation is completed before the data is read from reception buffer register 20)
Notes 1. Even when the stop bit length is set to 2 bits by setting bit 2 (SL20) of asynchronous serial
interface mode register 20 (ASIM20), the stop bit detection at reception is performed with 1 bit.
2. Be sure to read reception buffer register 20 (RXB20) when an overrun error occurs. If not, every
time the data is received an overrun error will occur.
User’s Manual U15075EJ1V0UM00
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NEC [ NEC ]
