2022-01-31 17:51:43 +01:00
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<title>GRAPHS</title>
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<!-- start of slide -->
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<div class="content">
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2025-01-03 11:46:17 +01:00
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2022-01-31 17:51:43 +01:00
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<h1>VIEWING SIMULATION DATA WITH XSCHEM</h1><br>
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<p>
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Usually when a spice simulation is done you want to see the results, this is usually accomplished
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with a waveform viewer. There are few open source viewers, like
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<a href="https://github.com/StefanSchippers/xschem-gaw">GAW</a>... <br>
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<img src="graphs02.png"><br>
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...Or ngspice internal plotting facilities:<br>
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<img src="graphs01.png"><br>
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There is also an interesting commercial product from Analog Flavor, called
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<a href="https://www.analogflavor.com/en/bespice/">BeSpice (bspwave)</a>
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that offers a free of charge one year evaluation license for non commercial use:<br>
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<img src="graphs03.png"><br>
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All these waveform viewers are supported by xschem and more can be added, just by giving the command line
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to start the viewer to xschem in the <kbd>Simulation-> Configure simulators and tools</kbd> dialog:<br>
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<img src="graphs04.png"><br>
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For <a href="">gaw</a>
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and
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2022-10-19 15:20:17 +02:00
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<a href="https://xschem.sourceforge.io/stefan/xschem_man/video_tutorials/probe_to_bespice.mp4">bespice</a>
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2022-01-31 17:51:43 +01:00
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xschem can automatically send nets to the viewer by clicking a net on the schematic
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and pressing the <kbd>Alt-G</kbd> key bind or by menu <kbd>Hilight->Send selected nets/pins to Viewer</kbd>
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<br>
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<img src="graphs05.png"><br>
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</p>
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2023-10-18 17:19:32 +02:00
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2022-10-18 16:30:11 +02:00
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<a id="graphs"><h2>Using XSCHEM's internal graph functions</h2></a>
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<p>
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Xschem can now display waveforms by itself in the drawing area. in the Simulation menu there is an entry to
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2023-12-18 23:36:01 +01:00
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add a graph: <kbd>Graph -> Add waveform graph</kbd>. When this menu is pressed a box can be placed in the schematic:
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2022-10-23 23:55:09 +02:00
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</p>
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<img src="graphs06.png">
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<p class="important">
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Xschem graphs are embedded into a rectangle object. Resizing graphs is done in the same way as resizing
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a rectangle object. See the <a href="commands.html#resize">related page</a>.
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To select a graph (to delete it or move it to a different position) click the left mouse button while in the area
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shown in this picture:
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</p>
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<img src="graphs16.png">
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<p>
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2022-01-31 17:51:43 +01:00
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The next step is loading the simulation data, This is done by menu
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<kbd>Waves->Op | Ac | Dc | Tran | Tran | Noise | Sp </kbd>. This command loads the user selected
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.raw file produced by a ngspice/Xyce simulation.
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2023-02-10 18:42:11 +01:00
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</p>
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<p>
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2023-12-18 23:36:01 +01:00
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The raw file is usually located in the simulation/netlisting directory
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<kbd>Simulation ->set netlist dir</kbd>.<br>
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After placing a graph box and loading simulation data a wave can be added. If you place the mouse on the inside
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of the box, close to the bottom/left/right edges and click the graph will be selected.
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You can also select a graph by dragging a selection rectangle all around it.
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This tells xschem where
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new nodes to be plotted will go, in case you have multiple graphs.
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Then, select a node or a net label, press 'Alt-G', the net will be added to the graph. Here after a
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list of commands you can perform in a graph to modify the viewport. These commands are active when
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the mouse is Inside the graph (you will notice the mouse pointer changing from an arrow to a <kbd>+</kbd>).
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2025-01-07 04:20:32 +01:00
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</p>
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<p class="important">
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if <kbd>set graph_use_ctrl_key 1</kbd> is set in the <kbd>xschemrc</kbd> file all bind keys shown
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below will need the <kbd>Control</kbd> key pressed to operate on the graphs. This setting can be used
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to make it more explicit when the user wants to operate on graphs. Without the <kbd>Control</kbd>
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key pressed the usual functions on schematic are performed instead of graph functions.<br>
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Example: the key <kbd>a</kbd> will create a symbol if used in a schematic while it shows a cursor
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if done when the mouse pointer is inside a graph. With the <kbd>set graph_use_ctrl_key 1</kbd> option
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you will need to press <kbd>Control-a</kbd> with the mouse pointer inside a graph to show a cursor.
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</p>
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<p>
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2022-01-31 17:51:43 +01:00
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if the mouse is outside the graph the usual Xschem functions will be available to operate on schematics:
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</p>
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<ul>
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<li>Pressing <kbd>f</kbd> with the mouse in the middle of the graph area will do a full X-axis zoom.</li>
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<li>Pressing <kbd>f</kbd> with the mouse on the left of the Y axis will do a full Y-axis zoom.</li>
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<li>Pressing <kbd>Left/Right</kbd> or <kbd>Up/Down</kbd> arrow keys while the mouse is inside a graph will
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move the waveforms to the left/right or zoom in/zoom out respectively.</li>
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2025-01-07 04:20:32 +01:00
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<li>Pressing <kbd>Left/Right</kbd> arrow keys while the mouse is on the left of the Y-axis
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will zoom in/zoom out in the Y direction.</li>
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<li>Pressing the <kbd>left</kbd> mouse button while the pointer is in the center of the graph
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will move the waves left or right following the pointer X movement.</li>
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<li>Pressing the <kbd>left</kbd> mouse button while the pointer is on the left of the Y-axis
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will move the waves high or low following the pointer Y movement.</li>
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<li> pressing <kbd>A</kbd> and/or <kbd>B</kbd> will show a horizontal cursor.
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The difference between the <kbd>A</kbd> and the <kbd>B</kbd> cursor is shown.</li>
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<li> pressing <kbd>a</kbd> and/or <kbd>b</kbd> will show a vertical cursor.
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The sweep variable difference between the <kbd>a</kbd> and the <kbd>b</kbd> cursor is shown and
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the values of all signals at the X position of the <kbd>a</kbd> cursor is shown. </li>
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<li> Double clicking the <kbd>left</kbd> mouse button with the pointer above a wave label will
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allow to change its color.</li>
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<li> Pressing the <kbd>right</kbd> mouse button with the pointer above a wave label will show it in bold.</li>
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<li> Double clicking the <kbd>left</kbd> mouse button with the pointer in the middle of the graph will show a
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configuration dialog box, where you can change many graph parameters.</li>
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<li> Pressing the <kbd>right</kbd> mouse button in the graph area and dragging some distance in the X direction
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will zoom in the waveforms to that X range.</li>
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2025-01-08 15:31:00 +01:00
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<li> Pressing the <kbd>right</kbd> mouse button to the left of the Y axis and dragging some distance in the Y direction
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will zoom in the waveforms to that Y range.</li>
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2022-01-31 17:51:43 +01:00
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</ul>
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<p>
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<img src="graphs07.png"><br>
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The graph configuration dialog box which is shown by <kbd>left</kbd> button double clicking inside the graph,
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allows to change many graph attributes, like number of X/Y labels, minor ticks, wave colors, add waves
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from the list of waves found in the raw file, select the dataset to show in case of multiple sweep simulations
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and more.<br>
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<img src="graphs08.png"><br>
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The text area with the colored wave names is just a text widget. You can manually edit it to add / remove waves,
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or you can place the cursor somewhere in the text, select some waves from the listbox on the left, press the
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<kbd>Add</kbd> button to have these waves added.
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If you place the insertion cursor in the middle of a node name in the text area, you can click the color
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radio buttons on the bottom to change the color. The <kbd>Search</kbd> entry can be used to restrict the list
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of nodes displayed in the listbox. The Search entry supports regular expression patterns. For example,
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<kbd>^X</kbd> will match all nodes that begin with <kbd>X</kbd>, <kbd>xm[0-9]\.</kbd> will match all nodes
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containing xm followed by one digit and a dot.
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</p>
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2023-10-18 17:19:32 +02:00
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2022-01-31 17:51:43 +01:00
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<h3>Display bus signals</h3>
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<p>
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If you have a design where digital signals are present you might want to group some of these to form a
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bus and display these bundled signals.
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After placing a graph box and loading the simulation data as explained above, left-double click the graph
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to show the configuration dialog, check the <kbd>bus</kbd> and <kbd>digital</kbd> check boxes,
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use the <kbd>Search</kbd> text entry to restrict the list of signals,
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then select all the signals you want to show as a bus and click the <kbd>Add</kbd> button. Also set the
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<kbd>Min value</kbd> and the <kbd>Max value</kbd> of the signals in the bus. This information is needed
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by Xschem to calculate the logic high and logic low thresholds. Currently the logic '1' is set at 80%
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of the signal min-max range and the logic '0' level is set at 20% of the signal range.
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After pressing the <kbd>Add</kbd> button a bus is shown in the text area. The first field is a template
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2022-02-15 01:28:29 +01:00
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<kbd>BUS_NAME</kbd> that you should change to give a meaningful name to the bus. The bus name is separated from
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the rest of bits by a <kbd>,</kbd> or <kbd>;</kbd> character.<br>
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2022-01-31 17:51:43 +01:00
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<img src="graphs09.png"><br>
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You will then see your bussed signal in the graph:<br>
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<img src="graphs10.png"><br>
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If you have bussed signals in the schematic , like <kbd>LDA[12:0]</kbd> and your graph has the
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<kbd>Digital</kbd> and <kbd>Bus</kbd> checkboxes set you can simply add the LDA bus to the graph by
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clicking the net in the schematic (with the configuration dialog open) and pressing <kbd>Alt-G</kbd>:<br>
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<img src="graphs11.png"><br>
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You can add many signals to see them stacked in a very compact view:<br>
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<img src="graphs12.png"><br>
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It is possible to switch the graph to analog mode, by unchecking the <kbd>Digital</kbd> checkbox in the graph
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configuration dialog, to better see the waveforms. Switching back to Digital yields the previous view.
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In analog mode buses are not shown, but are not lost. You will see them again when switching back to
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Digital mode. <br>
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<img src="graphs13.png"><br>
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Many graphs can be created in a schematic, and the configuration of all graphs (viewport, list of signals,
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colors) is saved together with the schematic. If you re-run a simulation just unloading/loading the data from
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the simulation menu will update the waveforms.<br>
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<img src="graphs14.png"><br>
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2022-02-15 01:28:29 +01:00
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<h3>Expression evaluation on waves</h3>
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<p>
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It is possible to enter math expressions combining simulation data, for example multiply current and
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voltage to get the power. The syntax of expressions uses postfix (RPN) notation. When entering an expression
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use double quotes in the graph edit attribute dialog box, so the expression will be considered as a single
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new wave to display. Operands are loaded onto a stack like structure and then evaluated.
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The syntax is: <br>
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<kbd>"alias_name;operand operand operator ..."</kbd><br>
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Example:<br>
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<kbd>"supply power;i(vcurrvnn) vnn * i(vcurrvpp) vpp * +"</kbd><br>
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that means: i(vcurrvnn) * vnn + i(vcurrvpp) * vpp.<br>
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<kbd>"i(vcurrvnn) 1e6 *"</kbd><br>
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that means: i(vcurrvnn) * 1e6.<br>
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<img src="graphs15.png"><br>
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The optional <kbd>alias_name</kbd> is just a string to display as the wave label instead of the whole expression.
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The following operators are defined:<br>
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3 argument operators:
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</p>
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<ul>
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<li><kbd>?</kbd> Conditional expression: X cond Y ? --> return X if cond = 1 else Y</li>
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</ul>
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<p>
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2 argument operators:
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</p>
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<ul>
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<li><kbd>+</kbd> Addition</li>
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<li><kbd>-</kbd> Subtraction</li>
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<li><kbd>*</kbd> Multiplication</li>
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<li><kbd>/</kbd> Division</li>
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<li><kbd><</kbd> Lower than</li>
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<li><kbd>></kbd> Greater than</li>
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<li><kbd>==</kbd> Equal</li>
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<li><kbd>!=</kbd> Not equal</li>
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<li><kbd><=</kbd> Lower or equal</li>
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<li><kbd>>=</kbd> Greater or equal</li>
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<li><kbd>==</kbd> Equal</li>
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<li><kbd>==</kbd> Equal</li>
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<li><kbd>**</kbd> Exponentiation</li>
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<li><kbd>max()</kbd> Take the maximum of the two operators</li>
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<li><kbd>min()</kbd> Take the minimum of the two operators</li>
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<li><kbd>exch()</kbd> Exchange top 2 operands on stack</li>
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<li><kbd>ravg()</kbd> Running average of over a specified time window</li>
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<li><kbd>del()</kbd> Delete waveform by specified quantity on the X-axis</li>
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<li><kbd>re()</kbd> Return real part of complex number specified as magnitude and phase (in deg)</li>
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<li><kbd>im()</kbd> Return imaginary part of complex number specified as magnitude and phase (in deg)</li>
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2022-02-15 01:28:29 +01:00
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</ul>
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<p>1 argument operators:</p>
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<ul>
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<li><kbd>sin()</kbd> Trig. sin function</li>
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<li><kbd>cos()</kbd> Trig. cos function</li>
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<li><kbd>tan()</kbd> Trig. tan function</li>
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2024-02-24 22:35:54 +01:00
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<li><kbd>sinh()</kbd> Hyp. sin function</li>
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<li><kbd>cosh()</kbd> Hyp. cos function</li>
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<li><kbd>tanh()</kbd> Hyp. tan function</li>
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<li><kbd>asinh()</kbd> Inv hyp. sin function</li>
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<li><kbd>acosh()</kbd> Inv hyp. cos function</li>
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<li><kbd>atanh()</kbd> Inv hyp. tan function</li>
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<li><kbd>asin()</kbd> Inverse trig. sin function</li>
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<li><kbd>acos()</kbd> Inverse trig. cos function</li>
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<li><kbd>atan()</kbd> Inverse trig. tan function</li>
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<li><kbd>cph()</kbd> Continuous phase. Instead of [-180, +180] discontinuities make phase continuous</li>
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2022-02-15 01:28:29 +01:00
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<li><kbd>sqrt()</kbd> Square root</li>
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<li><kbd>sgn()</kbd> Sign</li>
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<li><kbd>abs()</kbd> Absolute value</li>
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<li><kbd>exp()</kbd> Base-e Exponentiation</li>
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<li><kbd>ln()</kbd> Base-e logarithm</li>
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<li><kbd>log10()</kbd> Base 10 logarithm</li>
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2024-02-24 22:35:54 +01:00
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<li><kbd>idx()</kbd> point number (0, 1, 2, ...) in vector</li>
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2022-10-02 20:52:17 +02:00
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<li><kbd>db20()</kbd> Value in deciBel (20 * log10(n))</li>
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<li><kbd>avg()</kbd> Average</li>
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2022-11-02 00:47:59 +01:00
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<li><kbd>prev()</kbd> Delay waveform by one point (at any x-axis position take the previous value)</li>
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2022-09-16 13:19:26 +02:00
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<li><kbd>deriv()</kbd> Derivative w.r.t. graph sweep variable</li>
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<li><kbd>deriv0()</kbd> Derivative w.r.t. simulation (index 0) sweep variable</li>
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2022-02-15 01:28:29 +01:00
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<li><kbd>integ()</kbd> Integration</li>
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<li><kbd>dup()</kbd> Duplicate last element on stack</li>
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</ul>
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2023-10-18 17:19:32 +02:00
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2023-10-13 15:51:51 +02:00
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<h3>Display a specific dataset for a node</h3>
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<p>
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The following syntax:
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<kbd>node%n</kbd> where <kbd>node</kbd> is a saved node or a bus or an expression
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and <kbd>n</kbd> is an integer number will plot only the indicated dataset number.
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Dataset numbers start from 0.
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This syntax is accepted for single nodes, bus names and expressions:<br><br>
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2023-10-13 16:03:00 +02:00
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<kbd>"DATA_4; en, cal, saout % 4"</kbd><br>
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2023-10-13 15:51:51 +02:00
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<kbd>saout%3</kbd><br>
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2023-10-13 16:03:00 +02:00
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<kbd>"Power dataset 6; I(VVCC) VCC * %6"</kbd><br><br>
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2023-10-13 15:51:51 +02:00
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<img src="graphs17.png"><br>
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</p>
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2023-10-18 17:19:32 +02:00
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<h3>Specify a different raw file in a graph</h3>
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<p>
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It is now possible (xschem 3.4.5+) to load more raw files for a schematic in xschem.<br>
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Each graph may optionally refer to a different raw file.
|
2023-10-18 17:20:43 +02:00
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If you double click on a graph while waveforms are loaded you see the graphdialog dialog box:<br>
|
2023-10-18 17:19:32 +02:00
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<img src="graphs18.png"><br>
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The dialog box has now a simulation type listbox and a <kbd>Raw file:</kbd> text entry box.
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Specifying an existing .raw file name and a simulation type from the listbox
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will override the 'base' raw file loaded in xschem.
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(the 'base' raw file is the only one that was loaded previously and applied to all graphs)
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If no raw file is specified in a graph it will use the loaded 'base' raw file if any, like
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it used to work before.
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It is also possible to have multiple graphs all referring to the same raw file, each graph
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showing a different simulation. It is for example possible to show a dc, tran, ac simulation all
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loaded from a common .raw file.
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Image below shows an example: DC, AC, Transient simulation each one done with 3 runs
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varying the Bias current. In addition the <kbd>xschem annotate_op</kbd> is also used to
|
2024-06-27 15:59:42 +02:00
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annotate the operating point into the schematic.
|
2023-10-18 17:19:32 +02:00
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Ctrl-Left-button-clicking the <kbd>Backannotate</kbd> launcher will instantly update
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all graphs with data taken from the updated raw file(s).
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<br>
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<img src="graphs19.png"><br>
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</p>
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|
2024-01-22 15:22:39 +01:00
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<h3>Specify a different raw file for a single signal in a graph</h3>
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<p>
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The general syntax for a signal in a graph is the following:<br>
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<kbd>"alias_name; signal_name % dataset# raw_file sim_type</kbd><br>
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|
where:<br>
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<kbd>dataset#</kbd> is the dataset index to display (only meaningful and needed
|
2024-06-27 15:59:42 +02:00
|
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if multiple datasets are present like in Montecarlo / Mismatch simulations).
|
2024-06-11 15:14:41 +02:00
|
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|
If empty or -1 then show all datasets.<br>
|
2024-01-22 15:22:39 +01:00
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<kbd>raw_file</kbd> is the location and name of the raw file to load. You can use
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<kbd>$netlist_dir</kbd> to quickly reference the simulation directory where usually such
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raw files are located.<br>
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<kbd>sim_type</kbd> is the simulation type, like
|
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|
<kbd>ac</kbd>, <kbd>sp</kbd>, <kbd>spectrum</kbd>, <kbd>dc</kbd>, <kbd>op</kbd>,
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<kbd>tran</kbd>, <kbd>noise</kbd>.<br>
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|
Example:<br>
|
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|
<kbd>"SAOUT; saout % 2 $netlist_dir/autozero_comp.raw tran</kbd><br>
|
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|
<br>
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|
<img src="graphs20.png"><br>
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</p>
|
2023-10-18 17:19:32 +02:00
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|
2024-02-20 13:07:36 +01:00
|
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|
<h3>Change sweep variable</h3>
|
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|
<p> The graph dialog box has a <kbd>Sweep</kbd> textbox where you can write the
|
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|
X-axis variable. By default xschem uses the first variable in the raw file for the X-axis, and this is the
|
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|
sweep variable the simulation was done, so time for transients, frequency for AC sims, voltage or current sweep
|
2024-02-20 17:17:38 +01:00
|
|
|
for DC sims. Example below shows a cmos latch where a DC simulation has been done sweeping the voltage generator
|
2024-02-20 13:07:36 +01:00
|
|
|
on the <kbd>a</kbd> input from 0 to 3V.<br>
|
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|
<img src="graphs21.png"><br><br>
|
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|
If <kbd>v(a) v(z)</kbd> is specified in the Sweep textbox (or <kbd>a z</kbd>) the <kbd>z</kbd> signal
|
|
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|
will be plotted vs <kbd>a</kbd> and the <kbd>a</kbd> signal will be plotted vs <kbd>z</kbd>.<br>
|
|
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|
|
<img src="graphs22.png"><br><br>
|
|
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|
</p>
|
2023-10-18 17:19:32 +02:00
|
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|
2022-01-31 17:51:43 +01:00
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<!-- end of slide -->
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<div class="filler"></div>
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</div>
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<!-- frame footer -->
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<iframe seamless src="xschem_footer.html" class="footer_iframe" >
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</body>
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</html>
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