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CHAPTER 19 SERIAL INTERFACE CHANNEL 2
19.1 Serial Interface Channel 2 Functions
Serial interface channel 2 has the following three modes.
Operation stop mode
Asynchronous serial interface (UART) mode (with time-division transfer function)
3-wire serial I/O mode
(1) Operation stop mode
This mode is used when serial transfer is not carried out to reduce power consumption.
(2) Asynchronous serial interface (UART) mode (with time-division transfer function)
In this mode, one byte of data is transmitted/received following the start bit, and full-duplex operation is
possible.
A dedicated UART baud rate generator is incorporated, allowing communication over a wide range of baud
rates. In addition, the baud rate can be defined by scaling the input clock to the ASCK pin.
The MIDI standard baud rate (31.25 kbps) can be used by employing the dedicated UART baud rate generator.
Two sets of data I/O pins (RxD and TxD) are provided, and the pin to be used can be selected by software
(time-division transfer function). However, only one set of pins can be used at one time.
Cautions 1. If it is not necessary to change the data I/O pin, use of the RxD0/SI2/P70 and TxD0/SO2/
P71 pins is recommended. If only port 2 (RxD1/BUSY/P24 and TxD1/STB/P23) is used
as data I/O pins, the function of port 7 is limited.
2. When using the busy control option or busy & strobe control option in the three-wire
serial I/O mode with automatic transmit/receive function of the serial interface channel
1, the RxD1/BUSY/P24 and TxD1/STB/P23 pins cannot be used as data I/O pins.
(3) 3-wire serial I/O mode (MSB-first/LSB-first switchable)
In this mode, 8-bit data transfer is performed using three lines: the serial clock (SCK2), and serial data lines
(SI2, SO2).
In the 3-wire serial I/O mode, simultaneous transmission and reception is possible, increasing the data transfer
processing speed.
Either the MSB or LSB can be specified as the start bit for an 8-bit data serial transfer, allowing connection
to devices using either as the start bit.
The 3-wire serial I/O mode is useful for connection to peripheral I/Os and display controllers, etc., which
incorporate a conventional synchronous clocked serial interface, such as the 75X/XL Series, 78K Series, 17K
Series, etc.