NEC PD75402A Manuale Utente

The SBI (serial bus interface) is a high-speed serial interface which conforms to the the NEC serial bus format.

The SBI is a single-master high-speed serial bus. Its format includes the addition of bus configuration functions

to the clocked serial I/O method to enable communication to be performed with multiple devices using two signal

lines. Consequently, when a serial bus is configured with multiple microcomputers and peripheral ICs, it is possible

to reduce the number of ports used and the amount of wiring on the substrate.

The master can output to a slave on the serial data bus an address to select the target device for serial

communication, a command which gives a directive to the target device, and actual data. The slave can determine

by hardware whether the received data is an address, command or actual data. This function allows the serial

interface control portion of the application program to be simplified.

SBI functions are incorporated in a number of devices including the 75X series, and 78K series 8-bit single-chip

microcomputers.

An example of a serial bus configuration when CPUs and peripheral ICs with a serial interface conforming to the

SBI are used is shown in Fig. 5-32.

In the SBI the SB0 serial data bus pin is an open-drain output and thus the serial data bus line is in the wired-

OR state. The serial data bus line requires a pull-up resistor.

Master
CPU

SB0

SCK

Seroal Data Bis

Serial Clock

SB0

SCK

Slave CPU

Address 1

SB0

SCK

Slave CPU

Address 2

•  •  •

 

•  •  •

 

SB0

SCK

Slave IC

Address N

+ V

DD