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CHAPTER 5 EXPLANATION OF INSTRUCTIONS
Subtract Word
SUBW
Word Data Subtraction
[Instruction format]
SUBW dst, src
[Operation]
dst, CY
←
dst – src
[Operand]
Mnemonic
Operand(dst,src)
SUBW
AX, #word
[Flag]
Z
AC
CY
×
×
×
[Description]
The source operand (src) specified with the 2nd operand is subtracted from the destination operand (dst)
specified with the 1st operand and the result is stored in the destination operand (dst) and the CY flag.
The destination operand can be cleared to 0 by equalizing the source operand (src) and the destination
operand (dst).
If the subtraction shows that dst is 0, the Z flag is set to (1). In all other cases, the Z flag is cleared to (0).
If the subtraction generates a borrow out of bit 15, the CY flag is set to (1). In all other cases, the CY flag
is cleared to (0).
As a result of subtraction, the AC flag becomes undefined.
[Description example]
SUBW AX, #ABCDH;
ABCDH is subtracted from the AX register contents and the result is stored in the AX
register.