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ORA: Difference between revisions
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''' | {| class="wikitable" style="float:right;clear:right;width:50%" | ||
!colspan="8"|Basic Info | |||
|+ | |||
|'''Addressing Mode''' | |||
|'''Opcode''' | |||
|'''Length''' | |||
|'''Speed''' | |||
|+ | |||
|[[Immediate]] | |||
|09 | |||
|2 bytes | |||
|2 cycles* | |||
|+ | |||
|[[Absolute]] | |||
|0D | |||
|3 bytes | |||
|4 cycles* | |||
|+ | |||
|[[Absolute Long Addressing|Absolute Long]] | |||
|0F | |||
|4 bytes | |||
|5 cycles* | |||
|+ | |||
|[[Direct Page Addressing|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* | |||
|} | |||
{| class="wikitable" style="float:right;clear:right;width:30%" | {| class="wikitable" style="float:right;clear:right;width:30%" | ||
!colspan="8"|Flags | !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]] | ||
|+ | |+ | ||
| | | | ||
|. | |||
|. | |||
|. | |||
|. | |||
|. | |||
| | | | ||
| | |. | ||
|} | |} | ||
'''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 === | ||
* [[AND]] | * [[AND]] | ||
* [[EOR]] | * [[EOR]] | ||
=== External Links === | |||
* [[Eyes & Lichty]] page 471, on ORA: https://archive.org/details/0893037893ProgrammingThe65816/page/n497 | |||
* [[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:Inherited from 6502]] |
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
- 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
External Links
- Eyes & Lichty page 471, on ORA: https://archive.org/details/0893037893ProgrammingThe65816/page/n497
- 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