h8s-2138 Renesas Electronics Corporation., h8s-2138 Datasheet - Page 447

• Manufacturer Part Number: h8s-2138
• Description: Renesas 16-bit Single-chip Microcomputer H8s Family/h8s/2100 Series
• Manufacturer: Renesas Electronics Corporation.

15.2.3
TSR is a register used to transmit serial data.
To perform serial data transmission, the SCI first transfers transmit data from TDR to TSR, then
sends the data to the TxD pin starting with the LSB (bit 0).
When transmission of one byte is completed, the next transmit data is transferred from TDR to
TSR, and transmission started, automatically. However, data transfer from TDR to TSR is not
performed if the TDRE bit in SSR is set to 1.
TSR cannot be directly read or written to by the CPU.
15.2.4
TDR is an 8-bit register that stores data for serial transmission.
When the SCI detects that TSR is empty, it transfers the transmit data written in TDR to TSR and
starts serial transmission. Continuous serial transmission can be carried out by writing the next
transmit data to TDR during serial transmission of the data in TSR.
TDR can be read or written to by the CPU at all times.
TDR is initialized to H'FF by a reset, and in standby mode, watch mode, subactive mode, subsleep
mode, and module stop mode.
Bit
Initial value
Read/Write
Bit
Read/Write
Transmit Shift Register (TSR)
Transmit Data Register (TDR)
R/W
—
7
7
1
R/W
—
6
6
1
R/W
—
5
5
1
Section 15 Serial Communication Interface (SCI, IrDA)
R/W
—
4
4
1
Rev. 4.00 Jun 06, 2006 page 393 of 1004
R/W
—
3
3
1
R/W
—
2
2
1
R/W
—
REJ09B0301-0400
1
1
1
R/W
—
0
0
1