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CHAPTER 20 SERIAL INTERFACE CHANNEL 2
20.4.3 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 is set 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.
Caution Ensure that bit 0 and bits 3 through 6 are set to 0.
6543210<7>
Symbol
CSIM2 CSIE2 0 0 0 0
CSIM
22
CSCK 0
CSCK
0
1
Clock Selection in 3-wire Serial I/O Mode
Input clock from off-chip to SCK2 pin
Dedicated baud rate generator output
CSIM22
0
1
First Bit Specification
MSB
LSB
CSIE2
0
1
Operation Control in 3-wire Serial I/O Mode
Operation stopped
Operation enabled
FF72H 00H R/W
Address After Reset R/W