SH7032 Datasheet, PDF (383/687 Pages) Renesas Technology Corp – 32-Bit RISC Microcomputer

Section 13 Serial Communication Interface (SCI)
storage. 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 to RDR. RDR is initialized to H'00 by a reset and in standby
mode.
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
13.2.3 Transmit Shift Register
The transmit shift register (TSR) transmits serial data. The SCI loads transmit data from the
transmit data register (TDR) into 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
TDR into TSR and starts transmitting again. If the TDRE bit in SSR is 1, however, the SCI does
not load the TDR contents into TSR. The CPU cannot read or write to TSR directly.
Bit
7
6
5
4
3
2
1
0
Read/Write
—
—
—
—
—
—
—
—
13.2.4 Transmit Data Register
The transmit data register (TDR) is an eight-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 TDR into TSR and starts serial transmission. Continuous serial transmission is possible by
writing the next transmit data in TDR during serial transmission from TSR.
The CPU can always read and write to TDR. TDR is initialized to H'FF by a reset and in standby
mode.
Bit
7
6
5
4
3
2
1
0
Initial value
Read/Write
1
1
1
1
1
1
1
1
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Rev. 7.00 Jan 31, 2006 page 357 of 658
REJ09B0272-0700