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CHAPTER 13
SERIAL INTERFACE SIO0
User’s Manual U12790EJ2V0UD
(1) SBI functions
In the conventional serial I/O format, when a serial bus is configured by connecting two or more devices, many
ports and wiring are necessary to provide chip select signals to identify commands and data, and to judge
the busy state, because only the data transfer function is available. If these operations are to be controlled
by software, the software will become heavily loaded.
In SBI, a serial bus can be configured with two signal lines, one for the serial clock SCK0 and one for the serial
data bus SB0 (SB1). Thus, use of SBI leads to a reduction in the number of microcontroller ports and the
amount of wiring and routing on the board.
The SBI functions are described below.
(a) Address/command/data identification function
Serial data is distinguished as addresses, commands, and data.
(b) Chip select function by address transmission
The master executes slave chip selection by address transmission.
(c) Wakeup function
The slave can easily judge address reception (chip select judgment) with the wakeup function (which can
be set/reset by software).
When the wakeup function is set, the interrupt request signal (INTCSI0) is generated upon reception of
Thus, when communication is executed with two or more devices, the CPU of devices other than the
selected slave device can operate independent of serial communications.
(d) Acknowledge signal (ACK) control function
The acknowledge signal is controlled to check serial data reception.
(e) Busy signal (BUSY) control function
The busy signal is controlled to report the slave busy state.