https://rurandom.org/justintime/index.php?title=Sx_instruction_decision_tree&feed=atom&action=historySx instruction decision tree - Revision history2024-03-28T09:22:58ZRevision history for this page on the wikiMediaWiki 1.35.0https://rurandom.org/justintime/index.php?title=Sx_instruction_decision_tree&diff=1624&oldid=prevDanny at 21:36, 24 January 20152015-01-24T21:36:12Z<p></p>
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 21:36, 24 January 2015</td>
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<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>The image below shows a decision tree that can be used by an SX instruction decoder. Such a decoder could examine the bits of an instruction word from most significant (left) to least significant (right), starting at the root of the tree. Depending on the bit value found, the decoder takes either the '1' or the '0' branch. When the decoder reaches a labeled node, we have decoded enough bits to identify the instruction. Example: when the encoder finds the bit values 0, 1, 0, 1, we've identified the 'setb_fr_bit' ('''SETB <fr>.<bit>''') instruction.</div></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>The image below shows a decision tree that can be used by an SX instruction decoder. Such a decoder could examine the bits of an instruction word from most significant (left) to least significant (right), starting at the root of the tree. Depending on the bit value found, the decoder takes either the '1' or the '0' branch. When the decoder reaches a labeled node, we have decoded enough bits to identify the instruction. Example: when the encoder finds the bit values 0, 1, 0, 1, we've identified the 'setb_fr_bit' ('''SETB <fr>.<bit>''') instruction.</div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;"></ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">Instead of '1' and '0', there are a few 'x', or don't-care values in this tree. This means that an instruction decoder that is only interested in documented instructions does not have to look at the corresponding bit, because either the 0, or 1-branch don't lead to known instructions. I've used one of those branches to introduce a ''BREAKPOINT''-instruction, just for the SX emulator.</ins></div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[Image:Sx instruction decision tree.png]]</div></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[Image:Sx instruction decision tree.png]]</div></td></tr>
</table>Dannyhttps://rurandom.org/justintime/index.php?title=Sx_instruction_decision_tree&diff=697&oldid=prevDanny at 11:03, 14 January 20122012-01-14T11:03:05Z<p></p>
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 11:03, 14 January 2012</td>
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<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;">The image below shows a decision tree that can be used by an SX instruction decoder. Such a decoder could examine the bits of an instruction word from most significant (left) to least significant (right), starting at the root of the tree. Depending on the bit value found, the decoder takes either the '1' or the '0' branch. When the decoder reaches a labeled node, we have decoded enough bits to identify the instruction. Example: when the encoder finds the bit values 0, 1, 0, 1, we've identified the 'setb_fr_bit' ('''SETB <fr>.<bit>''') instruction.</ins></div></td></tr>
<tr><td colspan="2"> </td><td class='diff-marker'>+</td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div><ins style="font-weight: bold; text-decoration: none;"></ins></div></td></tr>
<tr><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[Image:Sx instruction decision tree.png]]</div></td><td class='diff-marker'> </td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>[[Image:Sx instruction decision tree.png]]</div></td></tr>
</table>Dannyhttps://rurandom.org/justintime/index.php?title=Sx_instruction_decision_tree&diff=324&oldid=prevDanny: 2 revisions: copying content from old site2010-07-12T22:07:38Z<p>2 revisions: copying content from old site</p>
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<td colspan="1" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 22:07, 12 July 2010</td>
</tr><tr><td colspan="2" class="diff-notice" lang="en"><div class="mw-diff-empty">(No difference)</div>
</td></tr></table>Dannyhttps://rurandom.org/justintime/index.php?title=Sx_instruction_decision_tree&diff=323&oldid=prevDanny: moved Sx instruction decision tree.png to Sx instruction decision tree2009-07-18T23:23:48Z<p>moved <a href="/justintime/index.php?title=Sx_instruction_decision_tree.png&action=edit&redlink=1" class="new" title="Sx instruction decision tree.png (page does not exist)">Sx instruction decision tree.png</a> to <a href="/justintime/w/Sx_instruction_decision_tree" title="Sx instruction decision tree">Sx instruction decision tree</a></p>
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<td colspan="1" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 23:23, 18 July 2009</td>
</tr><tr><td colspan="2" class="diff-notice" lang="en"><div class="mw-diff-empty">(No difference)</div>
</td></tr></table>Dannyhttps://rurandom.org/justintime/index.php?title=Sx_instruction_decision_tree&diff=322&oldid=prevDanny: Created page with 'Image:Sx instruction decision tree.png'2009-07-18T23:19:13Z<p>Created page with '<a href="/justintime/w/File:Sx_instruction_decision_tree.png" title="File:Sx instruction decision tree.png">Image:Sx instruction decision tree.png</a>'</p>
<p><b>New page</b></p><div>[[Image:Sx instruction decision tree.png]]</div>Danny