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User’s Manual U12790EJ2V0UD
CHAPTER 14 SERIAL INTERFACE SIO1
14.1 Functions of Serial Interface SIO1
Serial interface SIO1 employs the following three modes.
 Operation stop mode
 3-wire serial I/O mode
 3-wire serial I/O mode with automatic transmit/receive function
(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 (SCK1), serial output
(SO1) and serial input (SI1).
The 3-wire serial I/O mode enables simultaneous transmission/reception and so decreases the data transfer
processing time.
Since the start bit of 8-bit data to undergo serial transfer is switchable between MSB and LSB, connection
is enabled with either start bit device.
The 3-wire serial I/O mode is effective for connection of peripheral I/O units and display controllers which
incorporate a conventional clocked serial interface such as the 75XL, 78K and 17K Series.
(3) 3-wire serial I/O mode with automatic transmit/receive function (MSB-/LSB-first selectable)
This mode has an automatic transmit/receive function in addition to the functions in (2) above.
The automatic transmit/receive function is used to transmit/receive data with a maximum of 32 bytes. This
function enables the hardware to transmit/receive data to/from an OSD (On Screen Display) device and a
device with a built-in display controller/driver independently of the CPU, thus alleviating the software load.