movea.md

MOVEA - Move address

Operation

[An] ← [source]

Syntax

MOVEA <ea>,An

Attributes

Size word, longword

Description

Move the contents of the source to the destination location. The destination is an address register. The source must be a word or longword. If it is a word, it is sign-extended to a longword. The condition codes are not affected.

Application

The MOVEA instruction is used to load an address register (some assemblers simply employ the MOVE mnemonic for both MOVE and MOVEA). Note that the instruction LEA can often be used to perform the same operation (e.g., MOVEA.L #$1234,A0 is the same as LEA $1234,A0).

Take care because the MOVEA.W #$8000,A0 instruction sign-extends the source operand to $FFFF8000 before loading it into A0, whereas LEA $8000,A0 loads A0 with $00008000.

You should appreciate that the MOVEA and LEA instructions are not interchangeable. The operation MOVEA (Ai),An cannot be implemented by an LEA instruction, since MOVEA (Ai),An performs a memory access to obtain the source operand, as the following RTL demonstrates.

LEA (Ai),An = [An] ← [Ai]
MOVEA (Ai),An = [An] ← [M([Ai])]

Condition codes

X	N	Z	V	C
-	-	-	-	-

Source operand addressing modes

Dn	An	(An)	(An)+	‑(An)	(d,An)	(d,An,Xi)	ABS.W	ABS.L	(d,PC)	(d,PC,Xn)	imm
✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓	✓

From MOTOROLA M68000 FAMILY Programmer's reference manual. Copyright 1992 by Motorola Inc./NXP. Adapted with permission.