Hitachi H8/3006 Hardware Manual page 726

TDR—Transmit Data Register
7
Bit
Initial value 1
Read/Write R/W
6 5
1 1
R/W R/W R/W
Serial transmit data
H'FFFB3
4 3
1 1
R/W R/W
SCI0
2 1 0
1 1 1
R/W R/W
713