UPD75518 NEC, UPD75518 Datasheet - Page 103

• Manufacturer Part Number: UPD75518
• Description: 4 BIT SINGLE-CHIP MICROCOMPUTER
• Manufacturer: NEC

(4) 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. 4-47 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 serial
Master CPU
2. To switch between the master and slave, a pull-up resistor is required also for the serial clock
data bus line is placed in the wired OR state. A pull-up resistor is required for the serial data
bus line.
line (SCK0), because SCK0 input/output switching is performed between the master and
slave asynchronously.
SB0 (SB1)
Fig. 4-47 Example of SBI System Configuration
SCK0
Serial data bus
Serial clock
+V
DD
SB0 (SB1)
SCK0
SB0 (SB1)
SCK0
SB0 (SB1)
SCK0
Slave CPU
Address 1
Slave CPU
Address 2
Slave IC
Address N
PD75518(A)
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