IBM nec pd78p081(a2) User Manual
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CHAPTER 11 SERIAL INTERFACE CHANNEL 2
11.4.3 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 asynchro-
nous 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
Set 0 to the bits 0 and 3 to 6.
6
5
4
3
2
1
0
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