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CHAPTER 19 SERIAL INTERFACE CHANNEL 2
19.4.2 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 3-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.
(1) Register setting
UART mode (with time-division transfer function) is set with serial operating mode register 2 (CSIM2), the
asynchronous serial interface mode register (ASIM), the asynchronous serial interface status register (ASIS),
the baud rate generator control register (BRGC), and serial interface pin select register (SIPS).
(a) Serial operating mode register 2 (CSIM2)
CSIM2 is set with a 1-bit or 8-bit memory manipulation instruction.
RESET input clears CSIM2 to 00H.
When the UART mode is selected, 00H should be set in CSIM2.
Caution
Ensure that bits 0 and 3 to 6 are set to 0.
6
5
4
3
2
1
0
7
Symbol
CSIM2 CSIE2
0
0
0
0
CSIM
22
CSCK
0
CSCK
0
1
Clock Selection in 3-wire Serial I/O Mode
Input clock from off-chip to SCK2 pin
Dedicated baud rate generator output
CSIM22
0
1
First Bit Specification
MSB
LSB
CSIE2
0
1
Operation Control in 3-wire Serial I/O Mode
Operation stopped
Operation enabled
FF72H 00H
R/W
Address After Reset R/W