Fujitsu MB96300 series Hardware Manual page 73

F2mc-16fx 16-bit

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MB96300 Super Series Hardware Manual

Accumulator (A)

The accumulator (A) register consists of two 16-bit arithmetic operation registers (AH

and AL), and is used as a temporary storage for operation results and transfer data.

■ Accumulator (A)

The A register consists of two 16-bit arithmetic operation registers (AH and AL). The A register is used as a

temporary storage for operation results and transfer data. During 32-bit data processing, AH and AL are used

together. Only AL is used for word processing in 16-bit data processing mode or for byte processing in 8-bit

data processing mode (see Figure 2.4-2"32-bit data transfer" and Figure 2.4-3"AL-AH transfer"). The data

stored in the A register can be operated upon with the data in memory or registers (Ri, Rwi, or Rli). In the

same manner as with the F

item in AL is automatically sent to AH (data preservation function). The data preservation function and

operation between AL and AH help to improve processing efficiency.

When a byte or shorter data item is transferred to AL, the data is sign-extended or zero-extended and stored

as a 16-bit data item in AL. The data in AL can be handled either as word or byte.

When a byte-processing arithmetic operation instruction is executed on AL, the high-order eight bits of AL

before the operation are ignored. After the operation the heigh-order eight bits become zero.

The A register is not initialized by a reset. The A register holds an undefined value immediately after a reset.

MOVL A, @RW1+6

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of the A register