SH7011 Datasheet, PDF (202/292 Pages) Renesas Technology Corp – CMOS single-chip microprocessors

12.2.2 Receive Data Register (RDR)
The receive data register (RDR) stores serial receive data. The SCI completes the reception of one
byte of serial data by moving the received data from the receive shift register (RSR) into the RDR
for storage. The RSR is then ready to receive the next data. This double buffering allows the SCI
to receive data continuously.
The CPU can read but not write the RDR. The RDR is initialized to H'00 by a power-on reset.
Bit: 7
6
5
4
3
2
1
0
Initial value: 0
0
0
0
0
0
0
0
R/W: R
R
R
R
R
R
R
R
12.2.3 Transmit Shift Register (TSR)
The transmit shift register (TSR) transmits serial data. The SCI loads transmit data from the
transmit data register (TDR) into the TSR, then transmits the data serially from the TxD pin, LSB
(bit 0) first. After transmitting one data byte, the SCI automatically loads the next transmit data
from the TDR into the TSR and starts transmitting again. If the TDRE bit of the SSR is 1,
however, the SCI does not load the TDR contents into the TSR.
The CPU cannot read or write the TSR directly.
Bit: 7
6
5
4
3
2
1
0
R/W: —
—
—
—
—
—
—
—
12.2.4 Transmit Data Register (TDR)
The transmit data register (TDR) is an 8-bit register that stores data for serial transmission. When
the SCI detects that the transmit shift register (TSR) is empty, it moves transmit data written in the
TDR into the TSR and starts serial transmission. Continuous serial transmission is possible by
writing the next transmit data in the TDR during serial transmission from the TSR.
The CPU can always read and write the TDR. The TDR is initialized to H'FF by a power-on reset.
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