UPD75238GJ NEC [NEC], UPD75238GJ Datasheet - Page 99

• Manufacturer Part Number: UPD75238GJ
• Description: 4 BIT SINGLE-CHIP MICROCOMPUTER
• Manufacturer: NEC [NEC]

(d) SBI mode operation
The SBI (serial bus interface) is a high-speed serial interface that conforms to the NEC serial bus
format.
To allow communication with multiple devices on a single-master and high-speed serial bus using
two signal lines, the SBI has a bus configuration function added to the clock synchronous serial I/O
method. So the SBI can reduce ports and wires on boards when multiple microcomputers and
peripheral ICs are used to configure a serial bus.
Fig. 4-52 is an example of the SBI system configuration.
Cautions 1. In the SBI mode, the serial data bus pin SB0 (or SB1) is an open-drain output. So the
2. To switch between the master and slave, a pull-up resistor is required also for the serial
serial data bus line is placed in the wired OR state. A pull-up resistor is required for
the serial data bus line.
clock line (SCK0), because SCK0 input/output switching is performed between the
master and slave asynchronously.
Master CPU
PD75238
SB0 (SB1)
Fig. 4-52 Example of SBI System Configuration
SCK0
SB0 (SB1)
SCK0
SB0 (SB1)
SCK0
SB0 (SB1)
SCK0
Slave IC
Slave CPU
Slave CPU
PD75238
Address 1
Address 2
Address N
PD75238
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