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| <h4 class="subsection">9.23.2 Syntax</h4> |
| |
| <p><a name="index-M68HC11-syntax-1477"></a><a name="index-syntax_002c-M68HC11-1478"></a> |
| 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 (‘<samp><span class="samp">,</span></samp>’). In the normal mode, |
| <code>as</code> will complain if too many operands are specified for |
| a given instruction. In the MRI mode (turned on with ‘<samp><span class="samp">-M</span></samp>’ option), |
| it will treat them as comments. Example: |
| |
| <pre class="smallexample"> inx |
| lda #23 |
| bset 2,x #4 |
| brclr *bot #8 foo |
| </pre> |
| <p><a name="index-line-comment-character_002c-M68HC11-1479"></a><a name="index-M68HC11-line-comment-character-1480"></a>The presence of a ‘<samp><span class="samp">;</span></samp>’ character or a ‘<samp><span class="samp">!</span></samp>’ character anywhere |
| on a line indicates the start of a comment that extends to the end of |
| that line. |
| |
| <p>A ‘<samp><span class="samp">*</span></samp>’ or a ‘<samp><span class="samp">#</span></samp>’ 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 ‘<samp><span class="samp">#</span></samp>’ then as |
| well as starting a comment, the line could also be logical line number |
| directive (see <a href="Comments.html#Comments">Comments</a>) or a preprocessor control command |
| (see <a href="Preprocessing.html#Preprocessing">Preprocessing</a>). |
| |
| <p><a name="index-line-separator_002c-M68HC11-1481"></a><a name="index-statement-separator_002c-M68HC11-1482"></a><a name="index-M68HC11-line-separator-1483"></a>The M68HC11 assembler does not currently support a line separator |
| character. |
| |
| <p><a name="index-M68HC11-addressing-modes-1484"></a><a name="index-addressing-modes_002c-M68HC11-1485"></a>The following addressing modes are understood for 68HC11 and 68HC12: |
| <dl> |
| <dt><dfn>Immediate</dfn><dd>‘<samp><span class="samp">#</span><var>number</var></samp>’ |
| |
| <br><dt><dfn>Address Register</dfn><dd>‘<samp><var>number</var><span class="samp">,X</span></samp>’, ‘<samp><var>number</var><span class="samp">,Y</span></samp>’ |
| |
| <p>The <var>number</var> may be omitted in which case 0 is assumed. |
| |
| <br><dt><dfn>Direct Addressing mode</dfn><dd>‘<samp><span class="samp">*</span><var>symbol</var></samp>’, or ‘<samp><span class="samp">*</span><var>digits</var></samp>’ |
| |
| <br><dt><dfn>Absolute</dfn><dd>‘<samp><var>symbol</var></samp>’, or ‘<samp><var>digits</var></samp>’ |
| </dl> |
| |
| <p>The M68HC12 has other more complex addressing modes. All of them |
| are supported and they are represented below: |
| |
| <dl> |
| <dt><dfn>Constant Offset Indexed Addressing Mode</dfn><dd>‘<samp><var>number</var><span class="samp">,</span><var>reg</var></samp>’ |
| |
| <p>The <var>number</var> may be omitted in which case 0 is assumed. |
| The register can be either ‘<samp><span class="samp">X</span></samp>’, ‘<samp><span class="samp">Y</span></samp>’, ‘<samp><span class="samp">SP</span></samp>’ or |
| ‘<samp><span class="samp">PC</span></samp>’. 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. |
| |
| <br><dt><dfn>Offset Indexed Indirect</dfn><dd>‘<samp><span class="samp">[</span><var>number</var><span class="samp">,</span><var>reg</var><span class="samp">]</span></samp>’ |
| |
| <p>The register can be either ‘<samp><span class="samp">X</span></samp>’, ‘<samp><span class="samp">Y</span></samp>’, ‘<samp><span class="samp">SP</span></samp>’ or ‘<samp><span class="samp">PC</span></samp>’. |
| |
| <br><dt><dfn>Auto Pre-Increment/Pre-Decrement/Post-Increment/Post-Decrement</dfn><dd>‘<samp><var>number</var><span class="samp">,-</span><var>reg</var></samp>’ |
| ‘<samp><var>number</var><span class="samp">,+</span><var>reg</var></samp>’ |
| ‘<samp><var>number</var><span class="samp">,</span><var>reg</var><span class="samp">-</span></samp>’ |
| ‘<samp><var>number</var><span class="samp">,</span><var>reg</var><span class="samp">+</span></samp>’ |
| |
| <p>The number must be in the range ‘<samp><span class="samp">-8</span></samp>’..‘<samp><span class="samp">+8</span></samp>’ and must not be 0. |
| The register can be either ‘<samp><span class="samp">X</span></samp>’, ‘<samp><span class="samp">Y</span></samp>’, ‘<samp><span class="samp">SP</span></samp>’ or ‘<samp><span class="samp">PC</span></samp>’. |
| |
| <br><dt><dfn>Accumulator Offset</dfn><dd>‘<samp><var>acc</var><span class="samp">,</span><var>reg</var></samp>’ |
| |
| <p>The accumulator register can be either ‘<samp><span class="samp">A</span></samp>’, ‘<samp><span class="samp">B</span></samp>’ or ‘<samp><span class="samp">D</span></samp>’. |
| The register can be either ‘<samp><span class="samp">X</span></samp>’, ‘<samp><span class="samp">Y</span></samp>’, ‘<samp><span class="samp">SP</span></samp>’ or ‘<samp><span class="samp">PC</span></samp>’. |
| |
| <br><dt><dfn>Accumulator D offset indexed-indirect</dfn><dd>‘<samp><span class="samp">[D,</span><var>reg</var><span class="samp">]</span></samp>’ |
| |
| <p>The register can be either ‘<samp><span class="samp">X</span></samp>’, ‘<samp><span class="samp">Y</span></samp>’, ‘<samp><span class="samp">SP</span></samp>’ or ‘<samp><span class="samp">PC</span></samp>’. |
| |
| </dl> |
| |
| <p>For example: |
| |
| <pre class="smallexample"> ldab 1024,sp |
| ldd [10,x] |
| orab 3,+x |
| stab -2,y- |
| ldx a,pc |
| sty [d,sp] |
| </pre> |
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