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16.2 Configuration of Serial Interface UART0
Serial interface UART0 consists of the following hardware.
Item
Registers
Control registers
(1) Transmit shift register 0 (TXS0)
This is the register for setting transmit data. Data written to TXS0 is transmitted as serial data.
When the data length is set as 7 bits, bits 0 to 6 of the data written to TXS0 are transferred as transmit data.
Writing data to TXS0 starts the transmit operation.
TXS0 can be written by an 8-bit memory manipulation instruction. It cannot be read.
RESET input sets the value of this register to FFH.
Caution Do not write to TXS0 during a transmit operation.
The same address is assigned to TXS0 and receive buffer register 0 (RXB0). A read operation
reads values from RXB0.
(2) Receive shift register 0 (RX0)
This register converts serial data input via the RxD0 pin to parallel data. When one byte of data is received at
this register, the receive data is transferred to receive buffer register 0 (RXB0).
RX0 cannot be manipulated directly by a program.
(3) Receive buffer register 0 (RXB0)
This register is used to hold receive data. When one byte of data is received, one byte of new receive data is
transferred from the receive shift register (RX0).
When the data length is set as 7 bits, receive data is transferred to bits 0 to 6 of RXB0. In this case, the MSB
of RXB0 always becomes 0.
RXB0 can be read by an 8-bit memory manipulation instruction. It cannot be written to.
RESET input sets the value of this register to FFH.
Caution The same address is assigned to RXB0 and transmit shift register 0 (TXS0). During a write
operation, values are written to TXS0.
(4) Transmit controller
The transmit controller controls transmit operations, such as adding a start bit, parity bit, and stop bit to data that
is written to transmit shift register 0 (TXS0), based on the values set to asynchronous serial interface mode register
0 (ASIM0).
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CHAPTER 16 SERIAL INTERFACE UART0
Table 16-1. Configuration of Serial Interface (UART0)
Transmit shift register 0 (TXS0)
Receive shift register 0 (RX0)
Receive buffer register 0 (RXB0)
Asynchronous serial interface mode register 0 (ASIM0)
Asynchronous serial interface status register 0 (ASIS0)
Baud rate generator control register 0 (BRGC0)
User's Manual U15798EJ2V0UD
Configuration
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