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| <h4 class="subsection">9.48.2 Syntax</h4> |
| |
| <p><a name="index-XGATE-syntax-2236"></a><a name="index-syntax_002c-XGATE-2237"></a> |
| In XGATE RISC syntax, the instruction name comes first and it may |
| be followed by up to three operands. Operands are separated by commas |
| (‘<samp><span class="samp">,</span></samp>’). <code>as</code> will complain if too many operands are specified |
| for a given instruction. The same will happen if you specified too few |
| operands. |
| |
| <pre class="smallexample"> nop |
| ldl #23 |
| CMP R1, R2 |
| </pre> |
| <p><a name="index-line-comment-character_002c-XGATE-2238"></a><a name="index-XGATE-line-comment-character-2239"></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-XGATE-2240"></a><a name="index-statement-separator_002c-XGATE-2241"></a><a name="index-XGATE-line-separator-2242"></a>The XGATE assembler does not currently support a line separator |
| character. |
| |
| <p><a name="index-XGATE-addressing-modes-2243"></a><a name="index-addressing-modes_002c-XGATE-2244"></a>The following addressing modes are understood for XGATE: |
| <dl> |
| <dt><dfn>Inherent</dfn><dd>‘<samp></samp>’ |
| |
| <br><dt><dfn>Immediate 3 Bit Wide</dfn><dd>‘<samp><span class="samp">#</span><var>number</var></samp>’ |
| |
| <br><dt><dfn>Immediate 4 Bit Wide</dfn><dd>‘<samp><span class="samp">#</span><var>number</var></samp>’ |
| |
| <br><dt><dfn>Immediate 8 Bit Wide</dfn><dd>‘<samp><span class="samp">#</span><var>number</var></samp>’ |
| |
| <br><dt><dfn>Monadic Addressing</dfn><dd>‘<samp><var>reg</var></samp>’ |
| |
| <br><dt><dfn>Dyadic Addressing</dfn><dd>‘<samp><var>reg</var><span class="samp">, </span><var>reg</var></samp>’ |
| |
| <br><dt><dfn>Triadic Addressing</dfn><dd>‘<samp><var>reg</var><span class="samp">, </span><var>reg</var><span class="samp">, </span><var>reg</var></samp>’ |
| |
| <br><dt><dfn>Relative Addressing 9 Bit Wide</dfn><dd>‘<samp><span class="samp">*</span><var>symbol</var></samp>’ |
| |
| <br><dt><dfn>Relative Addressing 10 Bit Wide</dfn><dd>‘<samp><span class="samp">*</span><var>symbol</var></samp>’ |
| |
| <br><dt><dfn>Index Register plus Immediate Offset</dfn><dd>‘<samp><var>reg</var><span class="samp">, (</span><var>reg</var><span class="samp">, #</span><var>number</var><span class="samp">)</span></samp>’ |
| |
| <br><dt><dfn>Index Register plus Register Offset</dfn><dd>‘<samp><var>reg</var><span class="samp">, </span><var>reg</var><span class="samp">, </span><var>reg</var></samp>’ |
| |
| <br><dt><dfn>Index Register plus Register Offset with Post-increment</dfn><dd>‘<samp><var>reg</var><span class="samp">, </span><var>reg</var><span class="samp">, </span><var>reg</var><span class="samp">+</span></samp>’ |
| |
| <br><dt><dfn>Index Register plus Register Offset with Pre-decrement</dfn><dd>‘<samp><var>reg</var><span class="samp">, </span><var>reg</var><span class="samp">, -</span><var>reg</var></samp>’ |
| |
| <p>The register can be either ‘<samp><span class="samp">R0</span></samp>’, ‘<samp><span class="samp">R1</span></samp>’, ‘<samp><span class="samp">R2</span></samp>’, ‘<samp><span class="samp">R3</span></samp>’, |
| ‘<samp><span class="samp">R4</span></samp>’, ‘<samp><span class="samp">R5</span></samp>’, ‘<samp><span class="samp">R6</span></samp>’ or ‘<samp><span class="samp">R7</span></samp>’. |
| |
| </dl> |
| |
| <p>Convience macro opcodes to deal with 16-bit values have been added. |
| |
| <dl> |
| <dt><dfn>Immediate 16 Bit Wide</dfn><dd>‘<samp><span class="samp">#</span><var>number</var></samp>’, or ‘<samp><span class="samp">*</span><var>symbol</var></samp>’ |
| |
| <p>For example: |
| |
| <pre class="smallexample"> ldw R1, #1024 |
| ldw R3, timer |
| ldw R1, (R1, #0) |
| COM R1 |
| stw R2, (R1, #0) |
| </pre> |
| </dl> |
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