Node: M68HC11-Syntax, Next: M68HC11-Modifiers, Previous: M68HC11-Opts, Up: M68HC11-Dependent

### Syntax

In the M68HC11 syntax, the instruction name comes first and it may be followed by one or several operands (up to three). Operands are separated by comma (`,`). In the normal mode, `as` will complain if too many operands are specified for a given instruction. In the MRI mode (turned on with `-M` option), it will treat them as comments. Example:

         inx
         lda  #23
         bset 2,x #4
         brclr *bot #8 foo

The following addressing modes are understood for 68HC11 and 68HC12:

Immediate
  `#`number``
Address Register
  ``number`,X`, ``number`,Y`

  The number may be omitted in which case 0 is assumed.

Direct Addressing mode
  `*`symbol``, or `*`digits``
Absolute
  ``symbol``, or ``digits``

The M68HC12 has other more complex addressing modes. All of them are supported and they are represented below:

Constant Offset Indexed Addressing Mode
  ``number`,`reg``

  The number may be omitted in which case 0 is assumed. The register can be either `X`, `Y`, `SP` or `PC`. The assembler will use the smaller post-byte definition according to the constant value (5-bit constant offset, 9-bit constant offset or 16-bit constant offset). If the constant is not known by the assembler it will use the 16-bit constant offset post-byte and the value will be resolved at link time.

Offset Indexed Indirect
  `[`number`,`reg`]`

  The register can be either `X`, `Y`, `SP` or `PC`.

Auto Pre-Increment/Pre-Decrement/Post-Increment/Post-Decrement
  ``number`,-`reg`` ``number`,+`reg`` ``number`,`reg`-` ``number`,`reg`+`

  The number must be in the range `-8`..`+8` and must not be 0. The register can be either `X`, `Y`, `SP` or `PC`.

Accumulator Offset
  ``acc`,`reg``

  The accumulator register can be either `A`, `B` or `D`. The register can be either `X`, `Y`, `SP` or `PC`.

Accumulator D offset indexed-indirect
  `[D,`reg`]`

  The register can be either `X`, `Y`, `SP` or `PC`.

For example:

         ldab 1024,sp
         ldd [10,x]
         orab 3,+x
         stab -2,y-
         ldx a,pc
         sty [d,sp]