Freescale Semiconductor, Inc.
Ce ntra l Proc e ssor Unit (CPU)
3.8 Arithm e tic / Log ic Unit (ALU)
The ALU performs the arithmetic and logical operations defined by the
instruction set. The binary arithmetic circuits decode instructions and set
up the ALU for the selected operation. Most binary arithmetic is based
on the addition algorithm, carrying out subtraction as negative addition.
Multiplication is not performed as a discrete operation but as a chain of
addition and shift operations within the ALU. The multiply instruction
(MUL) requires 11 internal clock cycles to complete this chain of
operations.
General Release Specification
MC68HC705JJ7/MC68HC705JP7 — Rev. 3.0
Central Processor Unit (CPU)
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