
379
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 mode is equivalent to the 3-wire serial I/O mode with the addition of an automatic transmit/receive function.
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.
Caution
When using the P23/STB/TxD1 and P24/BUSY/RxD1 pins in the asynchronous serial interface
(UART) mode of serial interface channel 2, the busy control option and busy & strobe control
option are invalid.