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CHAPTER 16
SERIAL INTERFACE UART0 (
PD178076, 178078, AND 178F098 ONLY)
User’s Manual U12790EJ2V0UD
16.2 Configuration of Serial Interface UART0
Serial interface UART0 consists of the following hardware.
Table 16-1. 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 7 (PM7)
Port 7 (P7)
(1) Transmit shift register 0 (TXS0)
This register stores transmit data. The data written to TXS0 is transmitted as serial data.
When the data length is specified to be 7 bits, bits 0 to 6 of the data written to TXS0 are transferred as transmit
data. The transmission operation is started by writing data to TXS0.
TXS0 is written by an 8-bit memory manipulation instruction, but it cannot be read.
The value of this register is set to FFH after reset.
Caution
Do not write data to TXS0 during transmission.
Because TXS0 and receive buffer register 0 (RXB0) are assigned to the same address, if this
address is read, the value of RXB0 is read.
(2) Receive shift register 0 (RX0)
This register converts the serial data input to the RxD0 pin into parallel data. When 1 byte of data has been
received, the receive data is transferred to receive buffer register 0 (RXB0).
RXB0 cannot be directly manipulated by software.
(3) Receive buffer register 0 (RXB0)
This register holds receive data. Each time 1 byte of data has been received, new receive data is transferred
from receive shift register 0 (RX0).
If the data length is specified to be 7 bits, the receive data is transferred to bits 0 to 6 of RXB0, and the MSB
of RXB0 is always 0.
RXB0 can be read by an 8-bit memory manipulation instruction, but it cannot be written.
The value of this register is set to FFH after reset.
Caution
Because RXB0 and transmit shift register 0 (TXS0) are assigned to the same address, if data
is written to this address, the value is written to TXS0.