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DAS (SPC700): Difference between revisions
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!colspan="8"|Basic Info | !colspan="8"|Basic Info | ||
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|'''Speed''' | |'''Speed''' | ||
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| | |[[Accumulator Addressing | Accumulator]] | ||
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!colspan="8"|Flags | !colspan="8"|Flags Affected | ||
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|N | |[[Negative Flag|N]] | ||
|V | |[[Overflow Flag|V]] | ||
|P | |[[Direct Page Flag|P]] | ||
|B | |[[Break Flag|B]] | ||
|H | |[[Half-Carry Flag|H]] | ||
|I | |[[Interrupt Enable Flag|I]] | ||
|Z | |[[Zero Flag|Z]] | ||
|C | |[[Carry Flag|C]] | ||
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'''DAS''' (Decimal Adjust for Subtraction) is an [[SPC700]] instruction that performs the following: | |||
# If either the [[carry flag]] is clear or the accumulator exceeds 0x99, 0x60 is subtracted from the accumulator and the carry flag is cleared. | |||
# Then, if either the [[half-carry flag]] is clear or the low nibble of the accumulator exceeds 0x09, 0x06 is subtracted from the accumulator | |||
=== See Also === | === See Also === | ||
* [[DAA]] | * [[DAA]] | ||
* [[BCD]] | * [[BCD]] | ||
=== External Links === | |||
* Official Super Nintendo development manual on DAS: Table C-14 in [https://archive.org/details/SNESDevManual/book1/page/n233 Appendix C-8 of Book I] | |||
* [https://archive.org/details/SNESDevManual/book1/page/n180 page 3-8-2 of Book I], lbid | |||
* ares source code, SPC700::instructionDecimalAdjustSub | |||
[[Category:ASM]] | [[Category:ASM]] | ||
[[Category:SPC700]] | [[Category:SPC700]] | ||
[[Category:Decimal Compensation Commands]] | [[Category:Decimal Compensation Commands]] | ||
Latest revision as of 05:03, 27 November 2023
| Basic Info | |||||||
|---|---|---|---|---|---|---|---|
| Addressing Mode | Opcode | Length | Speed | ||||
| Accumulator | BE | 1 byte | 3 cycles | ||||
| Flags Affected | |||||||
|---|---|---|---|---|---|---|---|
| N | V | P | B | H | I | Z | C |
| . | . | . | . | . | |||
DAS (Decimal Adjust for Subtraction) is an SPC700 instruction that performs the following:
- If either the carry flag is clear or the accumulator exceeds 0x99, 0x60 is subtracted from the accumulator and the carry flag is cleared.
- Then, if either the half-carry flag is clear or the low nibble of the accumulator exceeds 0x09, 0x06 is subtracted from the accumulator
See Also
External Links
- Official Super Nintendo development manual on DAS: Table C-14 in Appendix C-8 of Book I
- page 3-8-2 of Book I, lbid
- ares source code, SPC700::instructionDecimalAdjustSub