38
The 68000's Instruction Set
[M(080001)] ← [D0(24:31)]
[M(080003)]
← [D0(16:23)]
[M(080005)]
← [D0(8:15)]
[M(080007)]
← [D0(0:7)]
Condition codes: X N Z C V
- - - - -
MOVEQ Move quick (copy a small literal to a
destination)
Operation: [destination] ← <literal>
Syntax: MOVEQ #<data>,Dn
Attributes: Size = longword
Description: Move the specified literal to a data register. The literal data is an
eight-bit field within the MOVEQ op-code and specifies a signed
value in the range -128 to +127. When the source operand is
transferred, it is sign-extended to 32 bits. Consequently, although
only 8 bits are moved, the MOVEQ instruction is a longword
operation.
Application: MOVEQ is used to load small integers into a data register. Beware
of its sign-extension. The two operations MOVE.B #12,D0 and
MOVEQ #12,D0 are not equivalent. The former has the effect
[D0(0:7)]←12, while the latter has the effect [D0(0:31)]←12 (with
sign-extension).
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