CHAPTER 11 SERIAL INTERFACE FUNCTION
User’s Manual U15109EJ3V0UD
329
(2) 3-wire serial I/O mode
3-wire serial I/O mode is useful when connecting to devices such as peripheral I/O that include a clocked serial
interface, and display controllers.
This mode executes data transfers via three lines: a serial clock line (SCKn), a serial output line (SOn), and a
serial input line (SIn).
(a) Register settings
3-wire serial I/O mode is set by serial operation mode register n (CSIMn).
Figure 11-3. CSIMn Setting (3-Wire Serial I/O Mode)
After reset:
00H
R/W
Address: CSIM0
FFFFF2A2H
CSIM2
FFFFF2C2H
CSIM3
FFFFF2D2H
<7>
6
5
4
3
2
1
0
CSIMn
CSIEn
0
0
0
0
MODEn
SCLn1
SCLn0
(n = 0, 2, 3)
SIOn operation enable/disable specification
CSIEn
Shift register operation
Serial counter
Port
1
Operation enabled
Count operation enabled
Serial fu port function
Transfer operation mode flag
MODEn
Operation mode
Transfer start trigger
SOn output
0
Transmit/receive mode
Write to SIOn
Normal output
1
Receive-only mode
Read from SIOn
Port function
SCLn2
SCLn1
SCLn0
Clock selection
0
0
0
External clock input (SCKn)
0
0
1
when n = 0, 3: TM5 output
when n = 2: TM6 output
0
1
0
f
XX
/8
0
1
1
f
XX
/16
1
0
0
Setting prohibited
1
0
1
Setting prohibited
1
1
0
f
XX
/32
1
1
1
f
XX
/64
Remarks
1.
Refer to
11.2.2 (1) Serial clock select register n (CSISn) and serial operation mode register
n (CSIMn)
for the SCLn2 bit.
2.
If the selected clock is specified as a timer output, the P17/T05/TI5 and P30/T06/TI6 pins do not
need to be in timer output mode.