DAS (SPC700): Difference between revisions

Revision as of 08:19, 4 July 2024


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, subtract 0x60 from the accumulator and clear the carry flag.
Then, if either the half-carry flag is clear or the low nibble of the accumulator exceeds 0x09, subtract 0x06 from the accumulator.

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

@@ Line 36: / Line 36: @@
 '''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.
+# If either the [[carry flag]] is clear or the accumulator exceeds 0x99, subtract 0x60 from the accumulator and clear the carry flag.
-# Then, if either the [[half-carry flag]] is clear or the low nibble of the accumulator exceeds 0x09, 0x06 is subtracted from the accumulator
+# Then, if either the [[half-carry flag]] is clear or the low nibble of the accumulator exceeds 0x09, subtract 0x06 from the accumulator.
 === See Also ===