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CHAPTER 15 SERIAL INTERFACE UART2
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User’s Manual U14260EJ3V1UD
15.2 Configuration of Serial Interface UART2
Serial interface UART2 includes the following hardware.
Table 15-1. Configuration of Serial Interface UART2
Item
Configuration
Registers
Transmit shift register 2 (TXS2)
Receive shift register 2 (RX2)
Transmit buffer register 2 (TXB2)
Receive buffer register 2 (RXB2)
Control registers
Asynchronous serial interface mode register 2 (ASIM2)
Asynchronous serial interface status register 2 (ASIS2)
Asynchronous serial interface transmit status register 2 (ASIF2)
Baud rate generator control register 2 (BRGC2)
Clock select register 2 (CKSEL2)
Transfer mode specification register 2 (TRMC2)
Port mode register 3 (PM3)
Port register 3 (P3)
(1) Transmit shift register 2 (TXS2)
This register transmits the data transferred from transmit buffer register 2 (TXB2), as serial data from the TxD2
pin.
The value of this register is set to FFH if bits 7 and 6 (TXE2) of asynchronous serial interface mode register 2
(ASIM2) are cleared to 0.
TXS2 cannot be manipulated directly by a program.
(2) Receive shift register 2 (RX2)
This register converts serial data input via the RxD2 pin to parallel data. When one byte of data is received at
this register, the receive data is transferred to receive buffer register 2 (RXB2).
RX2 cannot be manipulated directly by a program.
(3) Transmit buffer register 2 (TXB2)
This register sets data to be transmitted. The data written to TXB2 is transferred to transmit shift register 2 (RX2)
and transmitted from the TxD2 pin as serial data.
No data can be written to TXB2 if bit 1 (TXBF) of transmit status register 2 (ASIF2) is 1.
TXB2 is set by an 8-bit memory manipulation instruction.
RESET input sets TXB2 to FFH.
(4) Receive buffer register 2 (RXB2)
This register holds receive data. When one byte of data is received, one byte of new receive data is transferred
from the receive shift register (RX2).
When the data length is set as 7 bits, receive data is transferred to bits 0 to 6 of RXB2. In this case, the MSB
of RXB2 is always 0.
If an overrun error (OVE2) occurs, however, the receive data is not transferred to RXB2 but is discarded.
RXB2 can be read by an 8-bit memory manipulation instruction. It cannot be written.
The value of this register is also initialized to FFH at RESET input or by clearing bit 7 (POWER2) of asynchronous
serial interface mode register 2 (ASIM2) to 0.