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14.1 Serial Interface Functions
The serial interface SIO2 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 (SCK2), a serial output line (SO2), and
a serial input line (SI2).
Since simultaneous transmit and receive operations are enabled in the 3-wire serial I/O mode, the processing
time for data transfers is reduced.
The first bit in the 8-bit data in serial transfer is fixed as the MSB. This data contains a 1-byte receive buffer,
and can be received successively. The serial clock and the data phase/polarity can be selected.
The 3-wire serial I/O mode is useful for connection to a peripheral I/O device that includes a clocked serial
interface, a display controller, etc.
Figure 14-1 shows the serial interface SIO2 block diagram.
Serial receive buffer
status register
(SRBS2)
SDVA
SI2/P05
SO2/P04
SCK2/P03
CHAPTER 14 SERIAL INTERFACE SIO2
Figure 14-1. Serial Interface SIO2 Block Diagram
Internal bus
Receive buffer
SDOF
register (SIRB2)
Serial I/O shift register 2 (SIO2)
CSIE
Serial operation mode register 2 (CSIM2)
Internal bus
Preliminary User's Manual U14581EJ3V0UM00
Serial
Interrupt request
clock
signal generator
counter
Serial
clock
controller
CLPH
CLPO
MODE2
SCL21
INTCSI2
9
f
/2
X
10
Selector
f
/2
X
11
f
/2
X
SCL20
187
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