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CHAPTER 16 ASYNCHRONOUS SERIAL INTERFACE/3-WIRE SERIAL I/O
16.3 Operation
The asynchronous serial interface has the following two operation modes.
• Operation stop mode
• Asynchronous serial interface (UART) mode
16.3.1 Operation stop mode
Serial transfer cannot be performed in the operation stop mode, resulting in reduced power consumption.
Moreover, in the operation stop mode, pins can be used as regular ports.
(1) Register setting
Setting of the operation stop mode is done with asynchronous serial interface mode registers 1 and 2 (ASIM1,
ASIM2).
ASIM1 and ASIM2 are set by a 1-bit or 8-bit memory manipulation instruction.
RESET input sets ASIM1 and ASIM2 to 00H.
Address: 0FF70H, 0FF71H After reset: 00H
Symbol
7
ASIMn
TXEn
Note
Be sure to write "0" to bit 0.
Caution Switch across to the operational mode after stopping serial sending and receiving opera-
tions.
Remark n = 1, 2
268
R/W
6
5
4
RXEn
PSn1
PSn0
TXEn
RXEn
Operation mode
0
0
Operation stop
0
1
UART mode
(Receive only)
1
0
UART mode
(Transmit only)
1
1
UART mode
(Transmit/Receive)
User's Manual U12697EJ3V0UM
3
2
1
CLn
SLn
ISRMn
RxD1/P20, RxD2/P70
TxD1/P21, TxD2/P71
pin function
pin function
Port function
Port function
Serial function
Port function
Port function
Serial function
Serial function
Serial function
0
Note
0
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