9.24.2 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 presence of a `;' character or a `!' character anywhere on a line indicates the start of a comment that extends to the end of that line.

A `*' or a `#' character at the start of a line also introduces a line comment, but these characters do not work elsewhere on the line. If the first character of the line is a `#' then as well as starting a comment, the line could also be logical line number directive (see Comments) or a preprocessor control command (see Preprocessing).

The M68HC11 assembler does not currently support a line separator character.

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]