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User’s Manual U12790EJ2V0UD
CHAPTER 13 SERIAL INTERFACE SIO0
13.1 Functions of Serial Interface SIO0
Serial interface SIO0 employs the following five modes.
 Operation stop mode
 3-wire serial I/O mode
 SBI (serial bus interface) mode
 2-wire serial I/O mode
I2C (Inter IC) bus modeNote
Note
When using the I2C bus mode (including when this mode is implemented by software without using the
internal hardware), consult NEC Electronics when placing an order for a mask.
Caution
Do not change the operation mode (3-wire serial I/O, SBI, 2-wire serial I/O, or I2C bus) while
the operation of serial interface SIO0 is enabled. To change the operation mode, stop the serial
operation.
(1) Operation stop mode
This mode is used when serial transfer is not carried out to reduce power consumption.
(2) 3-wire serial I/O mode (MSB-/LSB-first selectable)
This mode is used for 8-bit data transfer using three lines, one each for the serial clock (SCK0), serial output
(SO0) and serial input (SI0). This mode enables simultaneous transmission/reception and therefore reduces
the data transfer processing time.
The start bit of transferred 8-bit data is switchable between the MSB and LSB, so that devices can be connected
regardless of their start bit recognition format.
This mode should be used when connecting with peripheral I/O devices or display controllers which incorporate
a conventional clocked serial interface as is the case with the 75XL, 78K, and 17K Series.