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3/22/2004
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Allegro Free Viewer 15.0
Installation Download from http://www.cadence.com/products/si_pk_bd/downloads/allegroviewers/index.aspx
Opening Files Allegro opens PCB files with a .brd extensionSimply select File->Open and navigate to the board file that you want to look at
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Allegro Free Viewer 15.0
Setting up the view Always best to start with a clean slateThis example sets up the board for viewing from the top sideTypically, start by zooming to fit the board to the windowAlso probably want to turn off the grid dots if they are on
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Click zoom-fit or hit F9 to see the whole boardClick on grid toggle, or hit Shift-F9 to toggle grid off
Allegro Free Viewer 15.0
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Allegro Free Viewer 15.0
Setting up the view Next, we need to clear the screen of the last-saved view settingsSelect Display->Color/VisibilitySet Global Visibility to “All Invisible” and hit apply
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Select Display->Color Visibility and set to “All Invisible”
Allegro Free Viewer 15.0
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Allegro Free Viewer 15.0
Setting up the view Select Group = Geometry and scroll down to check boxes next to
“Outline” under Board Geometry“Silkscreen_Top” under Board Geometry“Silkscreen_Top” under Package Geometry“Assembly_Top” under Package Geometry
Then select “Apply”
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Turn on the listed Geometry layers
Allegro Free Viewer 15.0
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Allegro Free Viewer 15.0
Setting up the view Select Group = Stack-Up and scroll down to check boxes next to
“Top” under Pin“Top” under Via“Top” under Etch
Then select “Apply”
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Turn on the listed Stack-Up layers
Allegro Free Viewer 15.0
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Allegro Free Viewer 15.0Layers
Allegro board files consist of many “layers”There are, for example, “etch” layers which are the actual copper connections There are also soldermask and silkscreen layers which correspond to the green outer coating and white labeling respectivelyAnd, there are other information-only layers that show dimensions, part outlines, etc.You will typically be focusing on the etch layers
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Allegro Free Viewer 15.0
Layers There is a quicker way to set visibility for etch layersOn the right hand side of the window there is a tab for “Visibility”You can use this to turn on and off signal and plane layers and the vias and device pads for those layers
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Allegro Free Viewer 15.0
Finding Nets You will normally want to look at a signal or set of signals, referred to in Allegro as “nets”To find a net, you can highlight itThere are two ways to highlight
Show Element (Temporary)Hilight (Must Dehilight to turn off)
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Allegro Free Viewer 15.0
Finding Nets After selecting either “Show Element” or “Hilight”, select the Find tab on the rightUnder “Find By Name” type in the name of the net and hit enter. You may use * as a wildcard if you are uncertain of the full net name or if you want to highlight a group of nets
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Allegro Free Viewer 15.0
Finding Nets Show Element will bring up an information window, zoom to the net, and highlight it
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Allegro Free Viewer 15.0
Finding Nets Highlight will simply zoom to the net, and highlight itYou must use “De-highlight” to turn off the net highlighting
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Allegro Free Viewer 15.0
Finding a group of nets
As mentioned, you can find multiple nets at once using a * as a wild-cardFor example, most clock signals include “CLK” as part of the net name.To find all clocks that have “CLK” in the net name, you can type in “*clk*” in the find filterThis will highlight all such nets
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Allegro Free Viewer 15.0
Hilight Color You can change either the Temporary (Show Element) or Permanent (Highlight) colorsAgain select “Display-> Color/Visibility” then change Group to “Display”Click on the color you want from the palette and select the colored box next to the appropriate highlight type
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Allegro Free Viewer 15.0
Finding and following long nets Long nets that span a large section of the board will be hard to see when Allegro zooms to fit the netAfter highlighting one of these nets, you will need to zoom in manuallyLook in the lower right corner and you will see a miniature display of the board outline along with the highlighted net.Click and drag a box around the net in this window to zoom in on itThen click on “Zoom Points” to allow you to draw a box around the highlighted item in the main window and zoom in further
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Allegro Free Viewer 15.0
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Allegro Free Viewer 15.0
Finding and following long nets After you have zoomed in on the net you will want to turn on all signal etch layers and shadow mode to make the net stand outFirst, go back to the Visibility tab on the right and check the box under “Etch” and next to “Conductors” Next, select “Display->Color/Visibility”, then the “Display” Group and turn Shadow mode “On”, check the box to “Dim active layer” and hit “Apply”
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Allegro Free Viewer 15.0
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Allegro Free Viewer 15.0
Finding and following long nets To follow the net, or to pan in general, press and hold the middle mouse button and drag your cursor in the main viewing windowIn this way you can follow the net where ever it goes
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Allegro Free Viewer 15.0
Finding etch length If you need to know the length of a net or a part of a net, you can get that information from the window that appears when you use “Show Element”If you use Show Element for a net, the window will list the entire net length
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Allegro Free Viewer 15.0Finding etch length
If you want to find the length of a section of the net, you can get either Cline or Cline Segment lengths. A Cline is any part of a net that routes on a single layer until it runs into a pin, via, or other feature.A Cline segment is any part of a net that routes on a single layer until it runs into a bend, pin, via or other feature. Basically, any single straight segment.This time, select Show Element, but instead, check the box for Cline or Cline Segment and the click on the segment you want to measure.
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Allegro Free Viewer 15.0
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