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2.5
Data Formats
The 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
Figure 2-10 shows 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
Register Number
RnH
RnL
RnH
RnL
RnH
RnL
Figure 2-10 General Register Data Formats
Data Format
7
0
7 6 5 4 3 2 1 0
Don't care
7
4 3
0
Upper
Lower
Don't care
7
0
MSB
LSB
Don't care
Don't care
7
0
7 6 5 4 3 2 1 0
Don't care
7
4 3
0
Upper
Lower
Don't care
7
0
MSB
LSB
41
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