NEC PD78F9488 - Manual (Page 216)

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User’s Manual U15331EJ4V1UD
CHAPTER 12 SERIAL INTERFACE 1A0
12.1 Function of Serial Interface 1A0
Serial interface 1A0 has 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 will not be performed. It enables a reduction in power consumption.
(2) 3-wire serial I/O mode (MSB/LSB-first switchable)
This mode is used to transfer 8-bit data using three lines: a serial clock line (SCK10) and two serial data lines
(SI10 and SO10).
Because this mode supports simultaneous transmission and reception, 3-wire serial I/O mode requires less
processing time for data transfer.
Also, when using 3-wire serial I/O mode, it is possible to select whether 8-bit data transfer will start with the
MSB or LSB, so any device can be connected regardless of whether that device is designed for MSB-first or
LSB-first transfers.
3-wire serial I/O mode is useful for connecting peripheral I/O circuits and display controllers with conventional
clocked serial interfaces, such as those found in the 75XL Series, 78K Series, and 17K Series.
(3) 3-wire serial mode with automatic transmit/receive function (MSB/LSB-first switchable)
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 16 bytes. This
function enables the hardware to transmit/receive data to/from the OSD (On Screen Display) device and a
device with an on-chip display controller/driver independently of the CPU, thus alleviating the software load.