uPD789871 Subseries 8-Bit Single-Chip Microcontrollers PUM

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CHAPTER 10 SERIAL INTERFACE 10
10.4.2 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 clocked serial interface, such as the 75XL Series, 78K Series, 17K Series, etc.
Communication is performed using three lines: the serial clock (SCK10), serial output (SO10), and serial input
(SI10).
(1) Register setting
3-wire serial I/O mode settings are performed using serial operation mode register 10 (CSIM10).
(a) Serial operation mode register 10 (CSIM10)
CSIM10 is set with a 1-bit or 8-bit memory manipulation instruction.
RESET input clears CSIM10 to 00H.
Symbol 6 5 4 3 2 1 0 Address After reset R/W
CSIM10
CSIE10 0 TPS101TPS100 0 DIR10 CSCK10 0
CSIE10
0
1
TPS101 TPS100
0
0
1
1
DIR10
0
1
CSCK10
0
1
Operation stopped
Operation enabled
0
1
0
1
MSB
LSB
fX/2 2 (1.25 MHz)
fX/2 3 (625 kHz)
fX/2 4 (313 kHz)
fX/2 5 (157 kHz)
Caution Bits 0, 3, and 6 must be set to 0.
Operation control in 3-wire serial I/O mode
Remarks 1. fX: Main system clock oscillation frequency
2. The parenthesized values apply to operation at fX = 5.0 MHz.
Preliminary User’s Manual U14938EJ1V0UM
FF72H 00H R/W
Count clock selection during operation enabled in 3-wire serial I/O mode
Input clock to SCK10 pin from external
Count clock selected by TPS100, TPS101
Start bit specification
Clock selection in 3-wire serial I/O mode