CHAPTER 20 EXPANDED I/O SERIAL INTERFACE
20.1 Overview of Expanded I/O Serial Interface
The expanded I/O serial interface is a serial I/O interface with an 8-bit/1-channel
configuration that is used to transfer data by clock synchronization. For data transfer,
LSB first or MSB first can be selected.
I Overview of expanded I/O serial interface
The expanded I/O serial interface has the following two operation modes:
•
Internal shift clock mode: This mode transfers data by synchronization with the internal clock.
•
External shift clock mode: This mode transfers data by synchronization with a clock that is
supplied via an external pin (SCK). Data can also be transferred in this mode by using a
general-purpose port that shares the external pin (SCK).
I Block diagram of expanded I/O serial interface
Figure 20.1-1 "Block diagram of expanded I/O serial interface" shows a block diagram of the
expanded I/O serial interface.
Figure 20.1-1 Block diagram of expanded I/O serial interface
(MSB First) D0 to D7
SIN1, 2
SOT1, 2
SCK1, 2
Internal clock
SMD2 SMD1 SMD0
378
Internal data bus
SDR (Serial data register)
Control circuit
2
1
0
SIE
SIR
Internal data bus
D7 to D0 (LSB First)
Select transfer direction
Shift clock counter
BUSY STOP
STRT MODE BDS SOE
Interrupt
request
Initial value
Read
Write
SCOE