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User
’
s Manual U14701EJ3V0UD
CHAPTER 16 SERIAL INTERFACE CSI1
16.4 Serial Interface CSI1 Operations
Serial interface CSI1 can be used in the following two modes.
Operation stop mode
3-wire serial I/O mode
16.4.1 Operation stop mode
Serial transfer is not executed in this mode. Therefore, the power consumption can be reduced. In addition, the
P23/SI1, P24/SO1, and P25/SCK1 pins can be used as normal I/O port pins in this mode.
(1) Register setting
The operation stop mode is set by serial operation mode register 1 (CSIM1).
(a) Serial operation mode register 1 (CSIM1)
This register is set by a 1-bit or 8-bit memory manipulation instruction.
RESET input sets the value of this register to 00H.
Address: FFB0H After reset: 00H R/W
Symbol
7
6
5
4
3
2
1
0
CSIM1
CSIE1
TRMD1
0
DIR1
0
0
0
CSOT1
CSIE1
Operation control in 3-wire serial I/O mode
0
Stops operation (SI1/P23, SO1/P24, and SCK1/P25 pins can be used as general-purpose port
pins).
1
Enables operation (SI1/P23, SO1/P24, and SCK1/P25 pins are at active level).
16.4.2 3-wire serial I/O mode
The 3-wire serial I/O mode is useful for connecting peripheral I/Os and display controllers having a conventional
clocked serial interface, such as the 75XL Series, 78K Series, and 17K Series.
In this mode, communication is executed by using three lines: serial clock (SCK1), serial output (SO1), and serial
input (SI1) lines.
(1) Register setting
The 3-wire serial I/O mode is set by using serial operation mode register 1 (CSIM1) and serial clock select register
1 (CSIC1).