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Chapter 26. M680x0 Dependent Features

26.2. Syntax

This syntax for the Motorola 680x0 was developed at mit.

The 680x0 version of

as

uses instructions names and syntax compatible with the Sun assembler.

Intervening periods are ignored; for example,

movl

is equivalent to

mov.l

.

In the following table

apc

stands for any of the address registers (

%a0

through

%a7

), the program

counter (

%pc

), the zero address relative to the program counter (

%zpc

), a suppressed address register

(

%za0

through

%za7

), or it may be omitted entirely. The use of

size

means one of

w

or

l

, and it may

be omitted, along with the leading colon, unless a scale is also specified. The use of

scale

means one

of

1

,

2

,

4

, or

8

, and it may always be omitted along with the leading colon.

The following addressing modes are understood:

Immediate

#number

Data Register

%d0

through

%d7

Address Register

%a0

through

%a7 %a7

is also known as

%sp

, i.e. the Stack Pointer.

%a6

is also known as

%fp

, the

Frame Pointer.

Address Register Indirect

%a0@

through

%a7@

Address Register Postincrement

%a0@+

through

%a7@+

Address Register Predecrement

%a0@ 

through

%a7@ 

Indirect Plus Offset

apc@(number)

Index

apc@(number,register:size:scale)

The

number

may be omitted.

Postindex

apc@(number)@(onumber,register:size:scale)

The

onumber

or the

register

, but not both, may be omitted.

Preindex

apc@(number,register:size:scale)@(onumber)

The

number

may be omitted. Omitting the

register

produces the Postindex addressing mode.

Absolute

symbol

, or

digits

, optionally followed by

:b

,

:w

, or

:l

.