MC68HC05X4 Datasheet, PDF (32/156 Pages) Motorola, Inc – HCMOS Microcontroller Unit

Freescale Semiconductor, Inc.
CPU
Arithmetic/Logic 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.
Instruction Set Overview
The MCU instruction set has 62 instructions and uses eight addressing
modes. The instructions include all those of the M146805 CMOS Family
plus one more: the unsigned multiply (MUL) instruction. The MUL
instruction allows unsigned multiplication of the contents of the
accumulator (A) and the index register (X). The high-order product is
stored in the index register, and the low-order product is stored in the
accumulator.
Addressing Modes
The CPU uses eight addressing modes for flexibility in accessing data.
The addressing modes provide eight different ways for the CPU to find
the data required to execute an instruction. The eight addressing modes
are:
• Inherent
• Immediate
• Direct
• Extended
• Indexed, no offset
MC68HC05X4
CPU
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