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2.5
Data Formats
The H8/300H CPU can process 1-bit, 4-bit (BCD), 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.
2.5.1
General Register Data Formats
Figures 2.6 and 2.7 show the data formats in general registers.
Data Type
1-bit data
1-bit data
4-bit BCD data
4-bit BCD data
Byte data
Byte data
Legend:
RnH: General register RH
RnL: General register RL
34
General
Register
RnH
RnL
RnH
RnL
RnH
RnL
Figure 2.6 General Register Data Formats
Data Format
7
0
7
6 5 4 3 2 1 0
7
Don't care
7 6 5 4 3 2 1 0
4 3
7
0
Upper digit
Lower digit
7
Don't care
Upper digit
7
0
MSB
LSB
7
Don't care
MSB
Don't care
0
Don't care
4 3
0
Lower digit
Don't care
0
LSB
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