GB Programming: Difference between revisions
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>ISSOtm (→Instructions get!: Remove instructions that don't exist on the Game Boy) |
>ISSOtm (→Flags: Remove flags that don't exist on Game Boy) |
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|Z||N||H||C||-||-||-||- |
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All "-" are unused flags. They are set to 0 at all times. |
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===S : Sign=== |
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If the accumulator is negative (from a signed perspective), the flag is set. You can also view it as a copy of the accumulator's 7th bit. |
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===Z : Zero=== |
===Z : Zero=== |
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===H : Half-Carry=== |
===H : Half-Carry=== |
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Works like the Carry flag, but referring to the least-significant ''nibble''. It is only used with the DAA instruction, so... forget it until then. |
Works like the Carry flag, but referring to the least-significant ''nibble''. It is only used with the DAA instruction, so... forget it until then. |
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===P/V : Parity/Overflow=== |
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This flag's meaning depends on the last operation. |
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If it means parity, it is set if the number of 1 in the accumulator is even. If it is odd, then it is reset. |
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If it means overflow, it is set if the last operation caused the accumulator's sign to change. |
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===N : Add/Subtract=== |
===N : Add/Subtract=== |
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