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Table Of Contents
Modern Computer Architecture and Organization - Third Edition
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Although this section includes detailed 6502 examples, it is intended to illustrate general architectural patterns, such as operand sourcing, address calculation, and control flow, which are broadly applicable to processors of all types.
We will examine the instruction categories available in the 6502 processor, beginning with memory and register data transfer instructions. We will continue with arithmetic, logical, and bit manipulation operations, and conclude with branching instructions, subroutine calls and returns, and interrupt-related instructions.
The 6502 uses load and store instructions to read data values from system memory into processor registers and to write register contents to memory. In the 6502 architecture, the LDA, LDX, and LDY instructions load the register identified in the instruction mnemonic with an 8-bit word from system memory. LDA supports all addressing modes available in the 6502, while LDX and LDY...