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19.4.3 3-wire serial I/O mode
The 3-wire serial I/O mode is useful for connection of peripheral I/Os and display controllers, etc., which incorporate
a conventional synchronous clocked serial interface, such as the 75X/XL series, 78K series, 17K series, etc.
Communication is performed using three lines: the serial clock (SCK2), serial output (SO2), and serial input (SI2).
(1) Register setting
3-wire serial I/O mode settings are performed using serial operating mode register 2 (CSIM2), the asynchronous
serial interface mode register (ASIM), and the baud rate generator control register (BRGC).
(a) Serial operating mode register 2 (CSIM2)
CSIM2 is set with a 1-bit or 8-bit memory manipulation instruction.
RESET input sets CSIM2 to 00H.
Symbol
<7>
6
5
CSIM2 CSIE2
0
0
Caution Ensure that bits 0 and 3 to 6 are set to 0.
CHAPTER 19 SERIAL INTERFACE CHANNEL 2
4
3
2
1
0
CSIM
0
0
CSCK
0
22
Address
After Reset
R/W
FF72H
00H
R/W
CSCK
Selection of Serial Operation Mode
0
UART mode
1
3-wire serial I/O mode
First Bit Specification
CSIM22
0
MSB
1
LSB
CSIE2
Operation Control in 3-wire Serial I/O Mode
0
Operation stopped
1
Operation enabled
467
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