12.2
Register Descriptions
12.2.1
Receive Shift Register (RSR)
Bit
7
6
5
4
3
2
1
0
Read/Write
—
—
—
—
—
—
—
—
RSR is a shift register that converts incoming serial data to parallel data. When one data character
has been received, it is transferred to the receive data register (RDR).
The CPU cannot read or write RSR directly.
12.2.2
Receive Data Register (RDR)
Bit
7
6
5
4
3
2
1
0
Initial value
Read/Write
0
0
0
0
0
0
0
0
R
R
R
R
R
R
R
R
RDR stores received data. As each character is received, it is transferred from RSR to RDR,
enabling RSR to receive the next character. This double-buffering allows the SCI to receive data
continuously.
RDR is a read-only register. RDR is initialized to H'00 by a reset and in the standby modes.
12.2.3
Transmit Shift Register (TSR)
Bit
7
6
5
4
3
2
1
0
Read/Write
—
—
—
—
—
—
—
—
TSR is a shift register that converts parallel data to serial transmit data. When transmission of one
character is completed, the next character is moved from the transmit data register (TDR) to TSR
and transmission of that character begins. If the TDRE bit is still set to 1, however, nothing is
transferred to TSR.
The CPU cannot read or write TSR directly.
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RENESAS [ RENESAS TECHNOLOGY CORP ]
