1.5 Data Formats
The H8/300H CPU can process 1-bit, 4-bit, 8-bit (byte), 16-bit (word), and 32-bit (longword)
data. Bit-manipulation instructions operate on 1-bit data by accessing bit n (n = 0, 1, 2, …, 7) of
byte operand data. The DAA and DAS decimal-adjust instructions treat byte data as two digits of
4-bit BCD data.
1.5.1 General Register Data Formats
Figure 1-10 shows the data formats in general registers.
Figure 1-10 General Register Data Formats
7 6 5 4 3 2 1 0
Don’t care
7
0
Don’t care
7 6 5 4 3 2 1 0
4 3
7
0
7
0
Don’t care
Upper
Lower
LSB
MSB
LSB
Data type
Register number
Data format
1-bit data
1-bit data
4-bit BCD data
4-bit BCD data
Byte data
Byte data
RnH
RnL
RnH
RnL
RnH
RnL
MSB
Don’t care
Upper
Lower
4 3
7
0
Don’t care
7
0
Don’t care
7
0
12