Filter
Top Products
21
CHAPTER 3 REGISTERS
3.3.2 Byte Data Transfer and Operation of Accumulator (A)
and Temporary Accumulator (T)
When data transfer to the accumulator (A) is performed byte-by-byte, the transfer data
is stored in the AL. Automatic data transfer to the temporary accumulator (T) is also
performed byte-by-byte and only the contents of the original AL are stored in the TL.
Neither the upper 8 bits of the accumulator nor the temporary accumulator are affected
by the transfer. Only the lower 8 bits are used for byte operation between the
accumulator and temporary accumulator. None of the upper 8 bits of the accumulator or
temporary accumulator are affected by the operation.
■ Example of Operation of Accumulator (A) and Temporary Accumulator (T) in Byte Data
Processing
An example of addition with carry of 8-bit data stored at addresses 1280
H
and 0042
H
is shown below.
Figure 3.3-8 shows the operation of the accumulator and temporary accumulator when the above example
is executed.
Figure 3.3-8 Operation of Accumulator and Temporary Accumulator in Byte Data Processing
MOV A, 0042H -
MOV A, 1280H
-
ADDC A -
A A A A
T T T CF 1 T
RAM RAM RAM RAM
56H 56H 56H 56H
EFH EFH EFH EFH
ABXXH
CDXXH
ABEFH
CDXXH
AB56H
CDEFH
AB 46H
CDEFH
1280H
0042H
...
1280H
0042H
1280H
0042H
1280H
0042H
...
...
...
...
...
...
...
Before execution
Last result
*2
*1
*1 The TH does not change when there is automatic data transfer to the temporary accumulator.
*2 The AH is not changed by the result of the addition of the AL, TL, and CF.
+