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SICP - A Simulator for Digital Circuits
<?xml version="1.0" encoding="UTF-8"?>
<!--Xholon Workbook http://www.primordion.com/Xholon/gwt/ MIT License, Copyright (C) Ken Webb, Fri Apr 11 2014 09:51:00 GMT-0400 (EDT)-->
<XholonWorkbook>
<Notes><![CDATA[
Xholon
------
Title: SICP - A Simulator for Digital Circuits
Description:
Url: http://www.primordion.com/Xholon/gwt/
InternalName: 10419442
Keywords:
My Notes
--------
This Xholon Workbook explores the `Simulator for Digital Circuits` model
described in section 3.3.4 of Abelson and Sussman's
`Structure and Interpretation of Computer Programs, second edition` book[1].
The book provides Scheme[8] code for one possible implementation of the model.
I've jotted down a few ideas in my journal, but I'm not yet sure which of
several Xholon-based approaches I'll proceed with.
The book is freely available online in several formats, including PDF[3], HTML5, and SVG.
This workbook includes one or more of the SVG images created by Andres Raba[4].
Goal:
- write as little code as possible
- how much can I do with structure only?
A Petri Net approach
--------------------
One promising approach is to implement the circuits as Petri Nets,
a mechanism that Xholon already supports.
Petri Net places represent the wires, which carry a signal with a value of 0 or 1.
Petri Net transitions represent the primitive functions,
which act on the values in the wires.
The circuits themselves are just containers for the primitive functions.
References
----------
(1) http://en.wikipedia.org/wiki/Structure_and_Interpretation_of_Computer_Programs
(2) http://sicpebook.wordpress.com/
(3) http://sicpebook.files.wordpress.com/2012/11/sicp.pdf
(4) https://github.com/sarabander/sicp
(5) https://github.com/robertberry/SICP-Exercises
(6) https://github.com/zodiac/isicp
(7) http://sarabander.github.io/sicp/
(8) http://en.wikipedia.org/wiki/Scheme_%28programming_language%29
]]></Notes>
<_-.XholonClass>
<DigitalSystem/>
<Wire superClass="PlacePN"/>
<PrimitiveFunctionBox superClass="TransitionPN">
<Inverter/>
<AndGate/>
<OrGate/>
</PrimitiveFunctionBox>
<!-- containers -->
<Circuit>
<HalfAdder/>
<FullAdder/>
</Circuit>
</_-.XholonClass>
<xholonClassDetails>
</xholonClassDetails>
<DigitalSystem>
<Wire roleName="a" token="1"/>
<Wire roleName="b" token="1"/>
<Wire roleName="s"/>
<Wire roleName="c"/>
<!-- Truth Table expected after several time steps when the circuit stabilizes
inputs outputs
a b s c
1 1 0 1
1 0 1 0
0 1 1 0
0 0 0 0
-->
<HalfAdder>
<Wire roleName="d"/>
<Wire roleName="e"/>
<OrGate kineticsType="KINETICS_LOGIC_OR"> <!-- KINETICS_LOGIC_OR 9 -->
<InputArcs>
<InputArc weight="1" connector="ancestor::DigitalSystem/Wire[@roleName='a']"/>
<InputArc weight="1" connector="ancestor::DigitalSystem/Wire[@roleName='b']"/>
</InputArcs>
<OutputArcs>
<OutputArc weight="1" connector="ancestor::HalfAdder/Wire[@roleName='d']"/>
</OutputArcs>
</OrGate>
<AndGate kineticsType="KINETICS_LOGIC_AND"> <!-- KINETICS_LOGIC_AND 8 -->
<InputArcs>
<InputArc weight="1" connector="ancestor::DigitalSystem/Wire[@roleName='a']"/>
<InputArc weight="1" connector="ancestor::DigitalSystem/Wire[@roleName='b']"/>
</InputArcs>
<OutputArcs>
<OutputArc weight="1" connector="ancestor::DigitalSystem/Wire[@roleName='c']"/>
</OutputArcs>
</AndGate>
<AndGate kineticsType="KINETICS_LOGIC_AND"> <!-- KINETICS_LOGIC_AND 8 -->
<InputArcs>
<InputArc weight="1" connector="ancestor::HalfAdder/Wire[@roleName='d']"/>
<InputArc weight="1" connector="ancestor::HalfAdder/Wire[@roleName='e']"/>
</InputArcs>
<OutputArcs>
<OutputArc weight="1" connector="ancestor::DigitalSystem/Wire[@roleName='s']"/>
</OutputArcs>
</AndGate>
<Inverter kineticsType="KINETICS_LOGIC_NOT"> <!-- KINETICS_LOGIC_NOT 10 -->
<InputArcs>
<InputArc weight="1" connector="ancestor::DigitalSystem/Wire[@roleName='c']"/>
</InputArcs>
<OutputArcs>
<OutputArc weight="1" connector="ancestor::HalfAdder/Wire[@roleName='e']"/>
</OutputArcs>
</Inverter>
</HalfAdder>
<PetriNet roleName="sicpDigitalCircuit01">
<QueueTransitions connector="ancestor::DigitalSystem"/>
<AnalysisPetriNet/>
<AnalysisCRN/>
<AnalysisCat/>
</PetriNet>
</DigitalSystem>
<Blockbehavior implName="org.primordion.xholon.base.Behavior_gwtjs"><![CDATA[
// TODO ?
]]></Blockbehavior>
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<dc:description>Based on the diagram in Abelson, Sussman &amp; Sussman's "Structure and Interpretation of Computer Programs", 2nd ed.</dc:description>
<dc:source>http://mitpress.mit.edu/sicp/full-text/book/book-Z-H-22.html#%_fig_3.25</dc:source>
<dc:creator>
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<dc:title>Andres Raba</dc:title>
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<dc:date>2012-11-17</dc:date>
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