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14.1 Functions of Serial Interface SIO3
Serial interface SIO3 has the following two modes.
(1) Operation stop mode
This mode is used when serial transfers are not performed. For details, see 14.4.1 Operation stop mode.
(2) 3-wire serial I/O mode (fixed as MSB first)
This is an 8-bit data transfer mode using three lines: a serial clock line (SCK3), serial output line (SO3), and
serial input line (SI3).
Since simultaneous transmit and receive operations are enabled in 3-wire serial I/O mode, the processing time
for data transfers is reduced.
The first bit of the serially transferred 8-bit data is fixed as the MSB.
3-wire serial I/O mode is useful for connection to a peripheral IC incorporating a clocked serial interface, or a
display controller, etc. For details, see 14.4.2 3-wire serial I/O mode.
Figure 14-1 shows a block diagram of the serial interface SIO3.
SI3/P20
SO3/P21
SCK3/P22
CHAPTER 14 SERIAL INTERFACE SIO3
Figure 14-1. Block Diagram of Serial Interface SIO3
Internal bus
User's Manual U15798EJ2V0UD
8
Serial I/O shift register
3 (SIO3)
Interrupt
Serial clock
request signal
counter
generator
Serial clock
controller
Selector
INTCSI3
3
f
/2
X
5
f
/2
X
7
f
/2
X
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