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CHAPTER 15 SERIAL INTERFACE CHANNEL 0 (
μ
PD78018F SUBSERIES)
(5) Transfer start
Serial transfer is started by setting the transfer data to the serial I/O shift register 0 (SIO0) when the following
two conditions are satisfied:
Operation control bit of serial interface channel 0 (CSIE0) = 1
When internal serial clock is stopped or SCK0 is high after 8-bit serial transfer
Caution
Even if CSIE0 is set to “1” after data has been written to SIO0, transfer is not started.
Serial transfer is automatically stopped at the end of 8-bit transfer, and an interrupt request flag (CSIIF0) is
set.
15.4.3 Operation in SBI mode
SBI (serial bus interface) is a high-speed serial interface mode conforming to NEC’s serial bus format.
SBI is a clocked serial I/O method in a format with a function for bus configuration added, so that a single master
can communicate with two or more devices with a high-speed serial bus consisting of two signal lines. Therefore,
the number of ports and wirings on a printed wiring board can be reduced when the serial bus consists of plural
microcomputers and peripheral ICs.
The master can output “addresses” that select the target device(s) for serial communication, “commands” that
directs the target device(s), and actual “data” to the slaves via serial data bus. A slave can identify the received data
as an “address”, “command”, or “data” by hardware. This function can simplify the application program which controls
the serial interface channel 0.
The SBI function is provided to some devices such as the 75X/XL series and the 78K series.
Figure 15-9 shows an example of configuration of the serial bus when a CPU or peripheral IC with a serial interface
conforming to SBI is used.
Because the serial data bus pin SB0 (SB1) in SBI is an open-drain output pin, the serial data bus line is wired-
ORed. A pull-up resistor is necessary for the serial data bus line.
When using the SBI mode, refer to
(11) Notes on SBI mode (d)
.