4 serial interface 20 operation, 1 operation stop mode – NEC PD78F9488 User Manual
Page 197
CHAPTER 11 SERIAL INTERFACE 20
User’s Manual U15331EJ4V1UD
197
11.4 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
11.4.1 Operation stop mode
In operation stop mode, serial transfer is not executed, thereby reducing the power consumption. The
P20/SCK20/ASCK20, P21/SO20/TxD20, and P22/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
0
0
0
0
DIR20
CSCK20
0
CSIM20
<7>
6
5
4
Symbol
Address
After reset
R/W
FF72H
00H
R/W
3
2
1
0
Caution Bits 0 and 3 to 6 must be set to 0.