AAS              ASCII Adjust after Subtraction      Flags: O D I T S Z A P C
?       ? ? * ? *

Logic:    If (AL & 0Fh) > 9 or AF = 1 then
AL   AL - 6
AH   AH - 1
AF   1;  CF   1
AF   0;  CF   0
AL   AL & 0Fh

AAS corrects the result of a previous subtraction of two valid
unpacked BCD operands, changing the content of AL to a valid BCD
number. The destination operand of the subtraction must have been
specified as AL. The high-order nibble of AL is always set to 0.

Operands                  Clocks   Transfers  Bytes   Example
no operands                 4          -        1     AAS

Note:          Unpacked BCD stores one digit per byte; AH contains
the most-significant digit and AL the least-
significant digit.

See also: AAA
See also: AAD
See also: AAS
See also: SUB
See also: SBB
See also: DAS
See also: Flags

AAS ASCII Adjust after Subtraction