| Load Accumulator With Memory |
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LDA (Load Accumulator With Memory) loads the accumulator with specified memory. It is probably the most-used opcode in 6502 assembly as it loads the most-used register. It is similar in function to LDX and LDY.
Operation
This pseudo C code shows how the LDA opcode functions when it is executed.
SET_NEGATIVE(Operand); // Clears the Negative Flag if the Operand is $#00-7F, otherwise sets it.
SET_ZERO(Operand); // Sets the Zero Flag if the Operand is $#00, otherwise clears it.
ACCUMULATOR = Operand; // Stores the Operand in the Accumulator Register.
Addressing Modes
| Addressing Mode
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Assembly Language Form
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Opcode
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# Bytes
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# Cycles
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| Immediate
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LDA #Operand
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A9
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2
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2
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| Zero Page
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LDA Operand
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A5
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2
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3
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| Zero Page, X
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LDA Operand, X
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B5
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2
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4
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| Absolute
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LDA Operand
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AD
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3
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4
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| Absolute, X
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LDA Operand, X
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BD
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3
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4*
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| Absolute, Y
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LDA Operand, Y
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B9
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3
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4*
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| (Indirect, X)
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LDA (Operand, X)
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A1
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2
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6
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| (Indirect), Y
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LDA (Operand), Y
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B1
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2
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5*
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| * Add 1 if page boundary is crossed.
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Examples
