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ORA: Difference between revisions

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|3 cycles*
|3 cycles*
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|+
|direct page indirect
|[[Direct Page Indirect]]
|12
|12
|2 bytes
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|5 cycles*
|5 cycles*
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|direct page indirect long
|[[Direct Page Indirect Long]]
|07
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|6 cycles*
|6 cycles*
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|stack relative
|[[Stack Relative]]
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!colspan="8"|Flags Affected
!colspan="8"|Flags Affected
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|+
|N
|[[Negative Flag|N]]
|V
|[[Overflow Flag|V]]
|M
|[[M Flag|M]]
|X
|[[X Flag|X]]
|D
|[[Decimal Flag|D]]
|I
|[[I Flag|I]]
|Z
|[[Zero Flag|Z]]
|C
|[[Carry Flag|C]]
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'''ORA''' is a 65x instruction that performs a logical OR. In all [[addressing modes]], ORA takes one extra cycle when the accumulator is 16 bits wide. In [[direct page addressing]] modes, ORA takes another extra cycle if the low byte of the [[direct page register]] is nonzero.
'''ORA''' is a 65x instruction that performs a logical OR and stores the result in the [[accumulator]].
 
===== Cycle Penalties =====
* In all [[addressing modes]], ORA takes one extra cycle when the accumulator is 16 bits wide.
* In [[direct page addressing]] modes, ORA takes another extra cycle if the low byte of the [[direct page register]] is nonzero.


=== See Also ===
=== See Also ===
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=== External Links ===
=== External Links ===
* [[Eyes & Lichty]] page on ORA: https://archive.org/details/0893037893ProgrammingThe65816/page/n497
* [[Eyes & Lichty]] page 471, on ORA: https://archive.org/details/0893037893ProgrammingThe65816/page/n497
* [[Labiak]] page on ORA: https://archive.org/details/Programming_the_65816/page/n166
* [[Labiak]] page 156 on ORA: https://archive.org/details/Programming_the_65816/page/n166
* [[MCS6500 Manual]] page on ORA: https://archive.org/details/mos_microcomputers_programming_manual/page/n36
* [[MCS6500 Manual]] page 21 on ORA: https://archive.org/details/mos_microcomputers_programming_manual/page/n36
* [[Carr]] page on ORA: https://archive.org/details/6502UsersManual/page/n279
* [[Carr]] page 266 on ORA: https://archive.org/details/6502UsersManual/page/n279
* [[Leventhal]] page on ORA: https://archive.org/details/6502-assembly-language-programming/page/n128
* [[Leventhal]] page 3-79 on ORA: https://archive.org/details/6502-assembly-language-programming/page/n128
* snes9x implementation of ORA: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L917
* snes9x implementation of ORA: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L917
* undisbeliever on ORA: https://undisbeliever.net/snesdev/65816-opcodes.html#ora-or-accumulator-with-memory
* undisbeliever on ORA: https://undisbeliever.net/snesdev/65816-opcodes.html#ora-or-accumulator-with-memory

Latest revision as of 04:19, 6 December 2023

Basic Info
Addressing Mode Opcode Length Speed
Immediate 09 2 bytes 2 cycles*
Absolute 0D 3 bytes 4 cycles*
Absolute Long 0F 4 bytes 5 cycles*
Direct Page 05 2 bytes 3 cycles*
Direct Page Indirect 12 2 bytes 5 cycles*
Direct Page Indirect Long 07 2 bytes 6 cycles*
absolute indexed by X 1D 3 bytes 4 cycles*
absolute long indexed by X 1F 4 bytes 5 cycles*
absolute indexed by Y 19 3 bytes 4 cycles*
direct page indexed by X 15 2 bytes 4 cycles*
direct page indexed indirect by X 01 2 bytes 6 cycles*
direct page indirect indexed by Y 11 2 bytes 5 cycles*
direct page indirect long indexed by Y 17 2 bytes 6 cycles*
Stack Relative 03 2 bytes 4 cycles*
stack relative indirect indexed by Y 13 2 bytes 7 cycles*
Flags Affected
N V M X D I Z C
. . . . . .

ORA is a 65x instruction that performs a logical OR and stores the result in the accumulator.

Cycle Penalties

See Also

External Links

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