CHAPTER 16 ASYNCHRONOUS SERIAL INTERFACE/3-WIRE SERIAL I/O
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User’s Manual U12697EJ3V0UM
16.2 Asynchronous Serial Interface Mode
The asynchronous serial interface (UART: Universal Asynchronous Receiver Transmitter) offers the following two
modes.
(1) Operation stop mode
This mode is used when serial transfer is not performed to reduce the power consumption.
(2) Asynchronous serial interface (UART) mode
This mode is used to send and receive 1-byte data that follows the start bit, and supports full-duplex transmission.
A UART-dedicated baud rate generator is provided on-chip, enabling transmission at any baud rate within a broad
range. The baud rate can also be defined by dividing the input clock to the ASCK pin.
The MIDI specification baud rate (31.25 Kbps) can be used by utilizing the UART-dedicated baud rate generator.
16.2.1 Configuration
The asynchronous serial interface includes the following hardware.
Figure 16-2 gives the block diagram of the asynchronous serial interface.
Table 16-2. Configuration of Asynchronous Serial Interface
Item
Configuration
Registers
Transmit shift registers 1, 2 (TXS1, TXS2)
Receive shift registers 1, 2 (RX1, RX2)
Receive buffer registers 1, 2 (RXB1, RXB2)
Control registers
Asynchronous serial interface mode registers 1, 2 (ASIM1, ASIM2)
Asynchronous serial interface status registers 1, 2 (ASIS1, ASIS2)
Baud rate generator control registers 1, 2 (BRGC1, BRGC2)
