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DAS (SPC700): Difference between revisions

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'''DAS''' (Decimal Adjust for Subtraction) is an [[SPC700]] instruction that performs the following:
'''DAS''' (Decimal Adjust for Subtraction) is an [[SPC700]] instruction that corrects a [[BCD]] difference:
# If either the [[carry flag]] is clear or the accumulator exceeds 0x99, subtract 0x60 from the accumulator and clear the carry flag.
# 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.
# Then, if either the [[half-carry flag]] is clear or the low nibble of the accumulator exceeds 0x09, subtract 0x06 from the accumulator.
The SPC700 has no [[decimal mode]].


==== Syntax ====
==== Syntax ====

Revision as of 22:23, 4 August 2024

Basic Info
Addressing Mode Opcode Length Speed
Accumulator BE 1 byte 3 cycles
Flags Affected
N V P B H I Z C
N . . . . . Z C

DAS (Decimal Adjust for Subtraction) is an SPC700 instruction that corrects a BCD difference:

  1. If either the carry flag is clear or the accumulator exceeds 0x99, subtract 0x60 from the accumulator and clear the carry flag.
  2. Then, if either the half-carry flag is clear or the low nibble of the accumulator exceeds 0x09, subtract 0x06 from the accumulator.

The SPC700 has no decimal mode.

Syntax

DAS
DAS A

See Also

External Links

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