Hitachi H8/3022 Hardware Manual page 622

TDR—Transmit Data Register
Bit
Initial value
Read/Write
7 6
1 1
R/W R/W
5 4
1 1
R/W R/W
Serial transmit data
H'B3
3 2
1 1
R/W R/W
SCI0
1 0
1 1
R/W R/W
613