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LDA: Difference between revisions

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'''LDA''' (Load Accumulator) is a 65x instruction that loads the accumulator.  In all [[addressing modes]], LDA takes one extra cycle when the accumulator is 16 bits wide. In [[direct page addressing]] modes, LDA takes another extra cycle if the low byte of the [[direct page register]] is nonzero. In both the [[Absolute Indexed]] and the DP Indirect Indexed by Y admodes, LDA takes an extra cycle if adding the index crosses a page boundary.
'''LDA''' (Load Accumulator) is a 65x instruction that loads the accumulator.  In [[immediate addressing]] only, LDA is a total of 3 bytes long when the accumulator is 16 bits wide.
 
===== Cycle Penalties =====
* In all [[addressing modes]], LDA takes one extra cycle when the accumulator is 16 bits wide.
* In [[direct page addressing]] modes, LDA takes another extra cycle if the low byte of the [[direct page register]] is nonzero.
* In both the [[Absolute Indexed]] and the DP Indirect Indexed by Y admodes, LDA takes an extra cycle if adding the index crosses a page boundary.


=== See Also ===
=== See Also ===

Revision as of 04:46, 20 November 2023

Basic Info
Addressing Mode Opcode Length Speed
Immediate A9 2 bytes* 2 cycles*
Absolute AD 3 bytes 4 cycles*
absolute long AF 4 bytes 5 cycles*
direct page A5 2 bytes 3 cycles*
direct page indirect B2 2 bytes 5 cycles*
direct page indirect long A7 2 bytes 6 cycles*
absolute indexed by X BD 3 bytes 4 cycles*
absolute long indexed by X BF 4 bytes 5 cycles*
absolute indexed by Y B9 3 bytes 4 cycles*
direct page indexed by X B5 2 bytes 4 cycles*
direct page indexed indirect by X A1 2 bytes 6 cycles*
direct page indirect indexed by Y B1 2 bytes 5 cycles*
direct page indirect long indexed by Y B7 2 bytes 6 cycles*
stack relative A3 2 bytes 4 cycles*
stack relative indirect indexed by Y B3 2 bytes 7 cycles*
Flags Affected
N V M X D I Z C
. . . . . .

LDA (Load Accumulator) is a 65x instruction that loads the accumulator. In immediate addressing only, LDA is a total of 3 bytes long when the accumulator is 16 bits wide.

Cycle Penalties

See Also

External Links

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