CHAPTER 12 SERIAL INTERFACE 20
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12.4 Serial Interface 20 Operation
Serial interface 20 provides the following three modes.
•
Operation stop mode
•
Asynchronous serial interface (UART) mode
•
3-wire serial I/O mode
12.4.1 Operation stop mode
In operation stop mode, serial transfer is not executed, thereby reducing the power consumption. The
P23/SCK20/ASCK20, P24/SO20/TxD20, and P25/SI20/RxD20 pins can be used as normal I/O ports.
(1)
Register setting
Operation stop mode is set by serial operation mode register 20 (CSIM20) and asynchronous serial
interface mode register 20 (ASIM20).
(a) Serial operation mode register 20 (CSIM20)
CSIM20 is set with a 1-bit or 8-bit memory manipulation instruction.
RESET input clears CSIM20 to 00H.
CSIE20
0
1
Operation control in 3-wire serial I/O mode
Operation disabled
Operation enabled
CSIE20
SSE20
0
0
DAP20
DIR20
CSCK20
CKP20
CSIM20
<7>
6
5
4
Symbol
Address
After reset
R/W
FF72H
00H
R/W
3
2
1
0
Caution
Bits 4 and 5 must be set to 0.
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