Intel 253666-024US - Manual (Page 306)

3-260 Vol. 2A DAS—Decimal Adjust AL after Subtraction
INSTRUCTION SET REFERENCE, A-M
Example
SUB AL, BL Before: AL = 35H, BL = 47H, EFLAGS(OSZAPC) = XXXXXX
After: AL = EEH, BL = 47H, EFLAGS(0SZAPC) = 010111
DAA Before: AL = EEH, BL = 47H, EFLAGS(OSZAPC) = 010111
After: AL = 88H, BL = 47H, EFLAGS(0SZAPC) = X10111
Flags Affected
The CF and AF flags are set if the adjustment of the value results in a decimal borrow
in either digit of the result (see the “Operation” section above). The SF, ZF, and PF
flags are set according to the result. The OF flag is undefined.
Protected Mode Exceptions
#UD If the LOCK prefix is used.
Real-Address Mode Exceptions
#UD If the LOCK prefix is used.
Virtual-8086 Mode Exceptions
#UD If the LOCK prefix is used.
Compatibility Mode Exceptions
#UD If the LOCK prefix is used.
64-Bit Mode Exceptions
#UD If in 64-bit mode.