diff --git a/doc/images/pstates.xml b/doc/images/pstates.xml
new file mode 100644
index 0000000..9279680
--- /dev/null
+++ b/doc/images/pstates.xml
@@ -0,0 +1 @@
+<mxGraphModel dx="1085" dy="551" grid="1" gridSize="10" guides="1" tooltips="1" connect="1" arrows="1" fold="1" page="0" pageScale="1" pageWidth="850" pageHeight="1100"><root><mxCell id="0"/><mxCell id="1" parent="0"/><mxCell id="4" style="edgeStyle=orthogonalEdgeStyle;rounded=0;orthogonalLoop=1;jettySize=auto;html=1;entryX=0;entryY=0.5;entryDx=0;entryDy=0;" edge="1" parent="1" source="2" target="3"><mxGeometry relative="1" as="geometry"/></mxCell><mxCell id="2" value="PIDLE" style="rounded=1;whiteSpace=wrap;html=1;" vertex="1" parent="1"><mxGeometry x="160" y="125" width="110" height="60" as="geometry"/></mxCell><mxCell id="7" style="edgeStyle=orthogonalEdgeStyle;rounded=0;orthogonalLoop=1;jettySize=auto;html=1;entryX=0.5;entryY=0;entryDx=0;entryDy=0;" edge="1" parent="1" source="3" target="6"><mxGeometry relative="1" as="geometry"/></mxCell><mxCell id="12" style="edgeStyle=orthogonalEdgeStyle;rounded=0;orthogonalLoop=1;jettySize=auto;html=1;entryX=0.5;entryY=0;entryDx=0;entryDy=0;" edge="1" parent="1" source="3" target="2"><mxGeometry relative="1" as="geometry"><Array as="points"><mxPoint x="425" y="90"/><mxPoint x="215" y="90"/></Array></mxGeometry></mxCell><mxCell id="18" style="edgeStyle=orthogonalEdgeStyle;rounded=0;orthogonalLoop=1;jettySize=auto;html=1;" edge="1" parent="1" source="3" target="16"><mxGeometry relative="1" as="geometry"><Array as="points"><mxPoint x="425" y="230"/><mxPoint x="235" y="230"/></Array></mxGeometry></mxCell><mxCell id="21" style="edgeStyle=orthogonalEdgeStyle;rounded=0;orthogonalLoop=1;jettySize=auto;html=1;" edge="1" parent="1" source="3" target="20"><mxGeometry relative="1" as="geometry"><Array as="points"><mxPoint x="425" y="230"/><mxPoint x="50" y="230"/></Array></mxGeometry></mxCell><mxCell id="29" style="edgeStyle=orthogonalEdgeStyle;rounded=0;orthogonalLoop=1;jettySize=auto;html=1;" edge="1" parent="1" source="3" target="28"><mxGeometry relative="1" as="geometry"><Array as="points"><mxPoint x="425" y="230"/><mxPoint x="-105" y="230"/></Array></mxGeometry></mxCell><mxCell id="3" value="PRUNNING" style="rounded=1;whiteSpace=wrap;html=1;" vertex="1" parent="1"><mxGeometry x="370" y="125" width="110" height="60" as="geometry"/></mxCell><mxCell id="5" value="Start()" style="text;html=1;strokeColor=none;fillColor=none;align=center;verticalAlign=middle;whiteSpace=wrap;rounded=0;" vertex="1" parent="1"><mxGeometry x="300" y="130" width="40" height="20" as="geometry"/></mxCell><mxCell id="10" style="edgeStyle=orthogonalEdgeStyle;rounded=0;orthogonalLoop=1;jettySize=auto;html=1;entryX=1;entryY=0.5;entryDx=0;entryDy=0;" edge="1" parent="1" source="6" target="3"><mxGeometry relative="1" as="geometry"><Array as="points"><mxPoint x="540" y="330"/><mxPoint x="540" y="155"/></Array></mxGeometry></mxCell><mxCell id="6" value="PTIMEOUT&lt;br&gt;t=T+m&lt;br&gt;PINTERRUPT" style="rounded=1;whiteSpace=wrap;html=1;" vertex="1" parent="1"><mxGeometry x="355" y="290" width="140" height="80" as="geometry"/></mxCell><mxCell id="8" value="delay(m)" style="text;html=1;strokeColor=none;fillColor=none;align=center;verticalAlign=middle;whiteSpace=wrap;rounded=0;" vertex="1" parent="1"><mxGeometry x="430" y="255" width="80" height="20" as="geometry"/></mxCell><mxCell id="11" value="t&amp;lt;T" style="text;html=1;strokeColor=none;fillColor=none;align=center;verticalAlign=middle;whiteSpace=wrap;rounded=0;" vertex="1" parent="1"><mxGeometry x="510" y="340" width="40" height="20" as="geometry"/></mxCell><mxCell id="13" value="end END" style="text;html=1;strokeColor=none;fillColor=none;align=center;verticalAlign=middle;whiteSpace=wrap;rounded=0;" vertex="1" parent="1"><mxGeometry x="310" y="50" width="40" height="20" as="geometry"/></mxCell><mxCell id="26" style="edgeStyle=orthogonalEdgeStyle;rounded=0;orthogonalLoop=1;jettySize=auto;html=1;entryX=0;entryY=0.5;entryDx=0;entryDy=0;" edge="1" parent="1" source="16" target="24"><mxGeometry relative="1" as="geometry"><Array as="points"><mxPoint x="235" y="430"/></Array></mxGeometry></mxCell><mxCell id="31" style="edgeStyle=orthogonalEdgeStyle;rounded=0;orthogonalLoop=1;jettySize=auto;html=1;" edge="1" parent="1" source="16"><mxGeometry relative="1" as="geometry"><mxPoint x="370" y="155" as="targetPoint"/><Array as="points"><mxPoint x="340" y="330"/><mxPoint x="340" y="155"/></Array></mxGeometry></mxCell><mxCell id="16" value="PSUSPENDED" style="rounded=1;whiteSpace=wrap;html=1;" vertex="1" parent="1"><mxGeometry x="160" y="290" width="150" height="80" as="geometry"/></mxCell><mxCell id="27" style="edgeStyle=orthogonalEdgeStyle;rounded=0;orthogonalLoop=1;jettySize=auto;html=1;" edge="1" parent="1" source="19"><mxGeometry relative="1" as="geometry"><mxPoint x="665" y="230" as="targetPoint"/></mxGeometry></mxCell><mxCell id="30" style="edgeStyle=orthogonalEdgeStyle;rounded=0;orthogonalLoop=1;jettySize=auto;html=1;dashed=1;" edge="1" parent="1" source="19" target="28"><mxGeometry relative="1" as="geometry"><Array as="points"><mxPoint x="665" y="200"/><mxPoint x="-105" y="200"/></Array></mxGeometry></mxCell><mxCell id="19" value="+&lt;br&gt;PHANDLER" style="rounded=1;whiteSpace=wrap;html=1;" vertex="1" parent="1"><mxGeometry x="610" y="125" width="110" height="60" as="geometry"/></mxCell><mxCell id="22" style="edgeStyle=orthogonalEdgeStyle;rounded=0;orthogonalLoop=1;jettySize=auto;html=1;entryX=0.5;entryY=0;entryDx=0;entryDy=0;" edge="1" parent="1" source="20" target="19"><mxGeometry relative="1" as="geometry"><Array as="points"><mxPoint x="50" y="430"/><mxPoint x="580" y="430"/><mxPoint x="580" y="105"/><mxPoint x="665" y="105"/></Array></mxGeometry></mxCell><mxCell id="20" value="PINTERRUPT" style="rounded=1;whiteSpace=wrap;html=1;" vertex="1" parent="1"><mxGeometry x="-20" y="290" width="140" height="80" as="geometry"/></mxCell><mxCell id="23" value="RaiseEvent()" style="text;html=1;strokeColor=none;fillColor=none;align=center;verticalAlign=middle;whiteSpace=wrap;rounded=0;" vertex="1" parent="1"><mxGeometry x="330" y="480" width="130" height="20" as="geometry"/></mxCell><mxCell id="24" value="+&lt;br&gt;PEVENTPEND" style="rounded=1;whiteSpace=wrap;html=1;" vertex="1" parent="1"><mxGeometry x="320" y="390" width="140" height="80" as="geometry"/></mxCell><mxCell id="28" value="PERROR" style="rounded=1;whiteSpace=wrap;html=1;" vertex="1" parent="1"><mxGeometry x="-160" y="290" width="110" height="80" as="geometry"/></mxCell><mxCell id="32" value="go" style="text;html=1;strokeColor=none;fillColor=none;align=center;verticalAlign=middle;whiteSpace=wrap;rounded=0;" vertex="1" parent="1"><mxGeometry x="300" y="255" width="40" height="20" as="geometry"/></mxCell><mxCell id="33" value="stop&lt;br&gt;INTERRUPT(0)" style="text;html=1;strokeColor=none;fillColor=none;align=center;verticalAlign=middle;whiteSpace=wrap;rounded=0;" vertex="1" parent="1"><mxGeometry x="110" y="250" width="120" height="20" as="geometry"/></mxCell><mxCell id="34" value="call" style="text;html=1;strokeColor=none;fillColor=none;align=center;verticalAlign=middle;whiteSpace=wrap;rounded=0;" vertex="1" parent="1"><mxGeometry x="680" y="200" width="40" height="20" as="geometry"/></mxCell></root></mxGraphModel>
\ No newline at end of file