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CHAPTER 14 SERIAL INTERFACE UART0
User
’
s Manual U14260EJ3V1UD
14.2 Configuration of Serial Interface UART0
Serial interface UART0 includes the following hardware.
Table 14-1. Configuration of Serial Interface UART0
Item
Configuration
Registers
Transmit shift register 0 (TXS0)
Receive shift register 0 (RX0)
Receive buffer register 0 (RXB0)
Control registers
Asynchronous serial interface mode register 0 (ASIM0)
Asynchronous serial interface status register 0 (ASIS0)
Baud rate generator control register 0 (BRGC0)
Port mode register 2 (PM2)
Port register 2 (P2)
(1) Transmit shift register 0 (TXS0)
This is a 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 TXS0 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), so 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 sent to bits 0 to 6 of RXB0. In this case, the MSB of RXB0
is always 0.
RXB0 can be read by an 8-bit memory manipulation instruction. It cannot be written.
RESET input sets RXB0 to FFH.
Caution
The same address is assigned to RXB0 and transmit shift register 0 (TXS0), so during a write
operation, values are written to TXS0.