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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'.


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