CHAPTER 11 SERIAL INTERFACE FUNCTION
User’s Manual U15109EJ3V0UD
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11.3.3 Operations
CSI4 has the following two operation modes.
•
Operation stopped mode
•
3-wire serial I/O mode
(1) Operation stopped mode
In this mode, serial transfers are not performed, thus enabling a reduction in power consumption.
In operation stopped mode, the SI4, SO4, and SCK4 pins can be used as normal I/O port pins.
(a) Register settings
Operation stopped mode is set via the CSIE4 bit of variable-length serial control register 4 (CSIM4). When
CSIE4 = 0 (SIO4 operation stop state), the pins connected to SI4, SO4, or SCK4 function as port pins.
Figure 11-7. CSIM4 Setting (Operation Stopped Mode)
After reset:
00H
R/W
Address: FFFFF2E2H
<7>
6
5
4
3
2
1
0
CSIM4
CSIE4
0
0
0
0
MODE4
0
SCL4
SIO4 operation enable/disable specification
CSIE4
Shift register operation
Serial counter
Port
0
Operation disabled
Cleared
Port function