Fujitsu F2MC-8FX manual Accumulator a and Temporary Accumulator T

CHAPTER 3 REGISTERS

3.3Accumulator (A) and Temporary Accumulator (T)

The accumulator (A) and temporary accumulator (T) are application-specific registers existing in the CPU.

The accumulator (A) is used as the area where the results of operations are temporarily stored.

The temporary accumulator (T) is used as the area where the old data is temporarily saved for data transfer to the accumulator (A) or the operand for operations.

■Accumulator (A)

For 16-bit operation all 16 bits are used as shown in Figure 3.3-1.For 8-bit operation only the lower 8 bits

are used as shown in Figure 3.3-2.

Figure 3.3-1 Accumulator (A) Operation (16-bit Operation)

Before execution

A 1234H

T5678H

CF 1

After execution

A 68ADH

T 5678H ADDCW A

CF 0

Figure 3.3-2 Accumulator (A) Operation (8-bit Operation)

Before execution

A 1234H

T5678H

CF 1

After execution

A 12ADH

T 5678H ADDC A

CF 0

■Temporary Accumulator (T)

When 16-bit data is transferred to the accumulator (A), all the old 16-bit data in the accumulator is transferred to the temporary accumulator (T) as shown in Figure 3.3-3.When 8-bit data is transferred to the accumulator, old 8-bit data stored in the lower 8 bits of the accumulator is transferred to the lower 8 bits of the temporary accumulator as shown in Figure 3.3-4.Although all 16-bits are used as the operand for 16-bit operations as shown in Figure 3.3-5,only the lower 8 bits are used for 8-bit operations as shown in Figure 3.3-6.

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