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6502 Addressing Modes
Category
Programming/Assembly

Topic
What are addressing modes? Most CPU instructions deal with the memory. When you access the memory, you can refer to it in various ways. For example, LDA $1021 would load memory location $1021 into the "A" register. Directly referring to memory location $1021 in this case is an example of "Absolute addressing mode". However, we could also use LDX #$21, LDA $1000,X. The ",X" part tells the CPU to look up the "X"th ($21th in this case) memory address from $1000. So esentially this example also reads the same memory location, but we've used "Absolute,X addressing mode".

The 6502 has the following 13 addressing modes:

Implicit addressing mode
Accumulator addressing mode
Immediate addressing mode
Zero Page addressing mode
Zero Page,X addressing mode
Zero Page,Y addressing mode
Relative addressing mode
Absolute addressing mode
Absolute,X addressing mode
Absolute,Y addressing mode
Indirect addressing mode
Indexed Indirect addressing mode
Indirect Indexed addressing mode



Keywords
addressing modes 



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