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CHAPTER 13
SERIAL INTERFACE SIO0
User’s Manual U12790EJ2V0UD
(3) SBI (serial bus interface) mode (MSB-first)
This mode is used for 8-bit data transfer with two or more devices using two lines, one for the serial clock (SCK0)
and one for the serial data bus (SB0 or SB1).
In the SBI mode, transfer data is classified into “addresses”, “commands” and “data” for transmission/
reception, in conformance with serial bus format of NEC Electronics.
Address:
Data to select the target device for serial communication
Command:
Data to give instructions to the target device
Data:
Data actually transferred
In fact, transfer is started when the master device outputs an “address” to the serial bus to select one of the
slave devices subject to communication. After that, “commands” and “data” are transmitted between the
master device and slave device to implement serial communication. The receiver can automatically identify
the received data as “addresses”, “commands”, or “data” by hardware.
This function enables the I/O ports to be used effectively and the application program serial interface control
portions to be simplified.
In this mode, the wakeup function for handshake and the acknowledge and busy signal output function can
also be used.
Figure 13-1. System Configuration Example of Serial Bus Interface (SBI)
Master CPU
SCK0
SB0
SCK0
SB0
Slave CPU1
SCK0
SB0
Slave CPU2
SCK0
SB0
Slave CPUn
VDD