UPD78F9418A NEC, UPD78F9418A Datasheet - Page 171

• Manufacturer Part Number: UPD78F9418A
• Description: (UPD7894xxA) 8-Bit Single Chip Microcontrollers
• Manufacturer: NEC

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13.1 Functions of Serial Interface 00
Serial interface 00 has the following three modes.
• Operation stopped mode
• Asynchronous serial interface (UART) mode
• 3-wire serial I/O mode
(1)
(2)
(3)
Operation stopped mode
This mode is used to reduce power consumption when serial transfer is not carried out.
Asynchronous serial interface (UART) mode
In this mode, one byte of data following the start bit is transmitted/received, and full-duplex operation is
possible.
A dedicated UART baud rate generator is incorporated, allowing communication over a wide range of baud
rates. In addition, the baud rate can be defined by dividing the clock input to the ASCK pin.
3-wire serial I/O mode (MSB/LSB start bit switchable)
In this mode, 8-bit data transfer is carried out using three lines, one for the serial clock (SCK) and two for
serial data (SI, SO).
The 3-wire serial I/O mode supports simultaneous transmit and receive operations, reducing data transfer
processing time.
It is possible to switch the start bit of 8-bit data to be transmitted between the MSB and the LSB, thus
allowing connection to devices with either start bit.
The 3-wire serial I/O mode is effective for connecting display controllers and peripheral I/Os such as the
75XL Series, 78K Series, and 17K Series, which have conventional clock synchronous serial interfaces.
CHAPTER 13 SERIAL INTERFACE 00
User’s Manual U13952EJ3V0UD
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