XOR (Super FX): Difference between revisions
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The low nybble of the opcode specifies either the immediate value or which general register to use, like OR. We can deduce this by contradiction because if it were the high nybble instead, [[RPIX]] would have the same opcode as XOR R<sub>4</sub> making them indistinguishable. | The low nybble of the opcode specifies either the immediate value or which general register to use, like OR. We can deduce this by contradiction because if it were the high nybble instead, [[RPIX]] would have the same opcode as XOR R<sub>4</sub> making them indistinguishable. | ||
[[HIB]]'s opcode is C0 and it appears to not care whether ALT1/ALT2 are set. If that is the case, then we can conclude that like OR, R<sub>0</sub> is not available as XOR's operand and neither can zero be the immediate value. (But R<sub>0</sub> can still be the source register.) | |||
The source and destination registers should be specified in advance using [[WITH]], [[FROM]], or [[TO]]. Otherwise, R<sub>0</sub> serves as the default. | The source and destination registers should be specified in advance using [[WITH]], [[FROM]], or [[TO]]. Otherwise, R<sub>0</sub> serves as the default. | ||
Revision as of 09:07, 22 July 2024
| Basic Info | |||||||
|---|---|---|---|---|---|---|---|
| Addressing Mode | Opcode | Length | Speed | ||||
| Immediate | 3FCn | 2 bytes | |||||
| Implied (type 1) | 3DCn | 2 bytes | |||||
| Flags Affected | ||||||||
|---|---|---|---|---|---|---|---|---|
| B | ALT1 | ALT2 | O/V | S | CY | Z | ||
| 0? | 0? | 0? | .? | ? | .? | ? | ||
XOR is an undocumented[dubious] (XOR is mentioned on page 2-2-7 of Book II of the Nintendo documentation) Super FX instruction that performs an exculsive or.
It probably restores the ALT0 state like OR.
The low nybble of the opcode specifies either the immediate value or which general register to use, like OR. We can deduce this by contradiction because if it were the high nybble instead, RPIX would have the same opcode as XOR R4 making them indistinguishable.
HIB's opcode is C0 and it appears to not care whether ALT1/ALT2 are set. If that is the case, then we can conclude that like OR, R0 is not available as XOR's operand and neither can zero be the immediate value. (But R0 can still be the source register.)
The source and destination registers should be specified in advance using WITH, FROM, or TO. Otherwise, R0 serves as the default.
Syntax
XOR Rn XOR #n
See Also
References
- https://en.wikibooks.org/wiki/Super_NES_Programming/Super_FX_tutorial#Instruction_Set_Table
- Example 3 on page 2-8-10 of Book II of the official Super Nintendo development manual