#### 8.19.2 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]