NEC PD78058FY(A) - Manual (Page 387)

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CHAPTER 18 SERIAL INTERFACE CHANNEL 1
18.1 Serial Interface Channel 1 Functions
Serial interface channel 1 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 switchable)
This mode is used for 8-bit data transfer using three lines, each for 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 valid for connection of peripheral I/O units and display controllers which
incorporate a conventional synchronous serial interface such as the 75X/XL, 78K and 17K Series.
(3) 3-wire serial I/O mode with automatic transmit/receive function (MSB-/LSB-first switchable)
This is the mode that an automatic transmit/receive function is appended to the above mode, (2) 3-wire serial
I/O mode.
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 the OSD (On Screen Display) device and a
device with built-in display controller/driver independently of the CPU, thus the software load can be alleviated.