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ORA: Difference between revisions

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'''ORA''' is a 65x instruction that performs a logical OR.
{| class="wikitable" style="float:right;clear:right;width:50%"
 
{| class="wikitable" style="float:right;clear:right;width:30%"
!colspan="8"|Basic Info
!colspan="8"|Basic Info
|+
|+
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|'''Speed'''
|'''Speed'''
|+
|+
|immediate
|[[Immediate]]
|09
|09
|2 bytes
|2 bytes
|2 cycles
|2 cycles*
|+
|+
|absolute
|[[Absolute]]
|0D
|0D
|3 bytes
|3 bytes
|4 cycles
|4 cycles*
|+
|+
|absolute long
|[[Absolute Long Addressing|Absolute Long]]
|0F
|0F
|4 bytes
|4 bytes
|5 cycles
|5 cycles*
|+
|+
|direct page
|[[Direct Page Addressing|Direct Page]]
|05
|05
|2 bytes
|2 bytes
|3 cycles
|3 cycles*
|+
|+
|direct page indirect
|[[Direct Page Indirect]]
|12
|12
|2 bytes
|2 bytes
|5 cycles
|5 cycles*
|+
|+
|direct page indirect long
|[[Direct Page Indirect Long]]
|07
|07
|2 bytes
|2 bytes
|6 cycles
|6 cycles*
|+
|+
|absolute indexed by X
|absolute indexed by X
|1D
|1D
|3 bytes
|3 bytes
|4 cycles
|4 cycles*
|+
|+
|absolute long indexed by X
|absolute long indexed by X
|1F
|1F
|4 bytes
|4 bytes
|5 cycles
|5 cycles*
|+
|+
|absolute indexed by Y
|absolute indexed by Y
|19
|19
|3 bytes
|3 bytes
|4 cycles
|4 cycles*
|+
|+
|direct page indexed by X
|direct page indexed by X
|15
|15
|2 bytes
|2 bytes
|4 cycles
|4 cycles*
|+
|+
|direct page indexed indirect by X
|direct page indexed indirect by X
|01
|01
|2 bytes
|2 bytes
|6 cycles
|6 cycles*
|+
|+
|direct page indirect indexed by Y
|direct page indirect indexed by Y
|11
|11
|2 bytes
|2 bytes
|5 cycles
|5 cycles*
|+
|+
|direct page indirect long indexed by Y
|direct page indirect long indexed by Y
|17
|17
|2 bytes
|2 bytes
|6 cycles
|6 cycles*
|+
|+
|stack relative
|[[Stack Relative]]
|03
|03
|2 bytes
|2 bytes
|4 cycles
|4 cycles*
|+
|+
|stack relative indirect indexed by Y
|stack relative indirect indexed by Y
|13
|13
|2 bytes
|2 bytes
|7 cycles
|7 cycles*
|}
|}


{| class="wikitable" style="float:right;clear:right;width:30%"
{| class="wikitable" style="float:right;clear:right;width:30%"
!colspan="8"|Flags Clobbered
!colspan="8"|Flags Affected
|+
|+
|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 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 21 on ORA: https://archive.org/details/mos_microcomputers_programming_manual/page/n36
* [[Carr]] page 266 on ORA: https://archive.org/details/6502UsersManual/page/n279
* [[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
* undisbeliever on ORA: https://undisbeliever.net/snesdev/65816-opcodes.html#ora-or-accumulator-with-memory


[[Category:ASM]]
[[Category:ASM]]
[[Category:Group One Instructions]]
[[Category:Group One Instructions]]
[[Category:Inherited from 6502]]
[[Category:Inherited from 6502]]

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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