
235
CHAPTER 13
SERIAL INTERFACE SIO0
User’s Manual U12790EJ2V0UD
13.4.2 3-wire serial I/O mode operation
The 3-wire serial I/O mode is effective for connection of peripheral I/O units and display controllers which
incorporate a conventional clocked serial interface as is the case with the 75XL, 78K, and 17K Series.
Communication is carried out with three lines, one each for the serial clock (SCK0), serial output (SO0), and serial
input (SI0).
(1) Register setting
The 3-wire serial I/O mode is set using serial operating mode register 0 (CSIM0), serial bus interface control
register 0 (SBIC0), port mode register 2 (PM2), and port 2 (P2).
(a) Serial operating mode register 0 (CSIM0)
CSIM0 is set by a 1-bit or 8-bit memory manipulation instruction.
Reset input sets CSIM0 to 00H.
Caution When using SCK0 or SCL, set P27 to 1. If P27 is set to 0, it always outputs a low level.
Notes 1. Bit 6 (COI) is a read-only bit.
2. Can be used as P25 (CMOS I/O) when used only for transmission.
3. Be sure to set WUP to 0 when the 3-wire serial I/O mode is selected.
Remark
×:
Don’t care
PM
××: Port mode register
P
××:
Output latch of port
<6>
<5>
4
3210
<7>
Symbol
CSIM0
CSIM01
0
Selection of serial interface SIO0 clock
Clock Input to SCK0/SCL/P27 pin from off-chip
0
SBI mode (refer to 13.4.3 SBI mode operation).
R/W
1
Clock specified by bits 0 to 3 of serial interface clock select register 0 (SCL0)
CSIM
04
0
FF60H
00H
R/WNote 1
Address
After reset
R/W
CSIM
03
CSIM
02
PM25 P25 PM26 P26 PM27 P27
Operating
mode
Start bit
SIO/SB0/SDA0/P25
pin function
SO0/SB1/SDA1/P26
pin function
SCK0/SCL/P27
pin function
×
10
WUP
0
1
Control of wakeup function
Interrupt request signal generated with each serial transfer in any mode
Setting prohibitedNote 3
R/W
1
MSB
LSB
1
×
0001
Note 2
3-wire serial
l/O mode
SI0
(Input)
SO0
(CMOS output)
SCK0
(CMOS I/O)
2-wire serial I/O mode (refer to 13.4.4 2-wire serial I/O mode operation) or
I2C bus mode (refer to 13.4.5 I2C bus mode operation).
11
Note 2
CSIE0
0
Control of serial interface SIO0 operation
Operation stopped
Operation enabled
R/W
1
CSIE0 COI
WUP CSIM04 CSIM03 CSIM02 CSIM01
0