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UCD EEC 116 - The Interactive Router

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Magic Tutorial #10: The Interactive RouterMichael ArnoldO DivisionLawrence Livermore National LaboratoryLivermore, CA 94550This tutorial corresponds to Magic version 7.Tutorials to read first:Magic Tutorial #1: Getting StartedMagic Tutorial #2: Basic Painting and SelectionMagic Tutorial #4: Cell HierarchiesCommands introduced in this tutorial::irouteMacros introduced in this tutorial:ˆR, ˆN1 IntroductionThe Magic interactive router, Irouter, provides an interactive interface to Magic’s internal mazerouter. It is intended as an aid to manual routing. Routing is done one connection at a time, theuser specifying a starting point and destination areas prior to each connection. The user determinesthe order in which signals are routed and how multi-point nets are decomposed into point-to-areaconnections. In addition parameters and special Magic hint layers permit the user to control thenature of the routes. Typically the user determines the overall path of a connection, and leaves thedetails of satisfying the design-rules, and detouring around or over minor obstacles, to the router.The interactive router is not designed for fully automatic routing: interactions between nets arenot considered, and net decomposition is not automatic. Thus netlists are generally not suitableinput for the Irouter. However it can be convenient to obtain endpoint information from netlists.The Net2ir program uses netlist information to generate commands to the Irouter with appropriateendpoints for specified signals. Typically a user might setup parameters and hints to river-route a–1–September 26, 2001 Magic Tutorial #10: The Interactive Routerset of connections, and then generate Irouter commands with the appropriate endpoints via Net2ir.For details on Net2ir see the manual page net2ir(1).This tutorial provides detailed information on the use of the Irouter. On-line help, Iroutersubcommands, Irouter parameters, and hint-layers are explained.2 Getting Started—‘Cntl-R’, ‘Cntl-N’, ‘:iroute’ and ‘:iroute help’To make a connection with the Irouter, place the cursor over one end of the desired connection (thestart-point) and the box at the other end (the destination-area). Then typeCntl-RNote that the box must be big enough to allow the route to terminate entirely within it. Adesign-rule correct connection between the cursor and the box should appear. The macroCntl-Rand the long commands:iroute:iroute routeare all equivalent. They invoke the Irouter to connect the cursor with the interior of the box.Note that the last connection is always left selected. This allows further terminals to be connectedto the route with the second Irouter macro, Cntl-N. Try typingCntl-NA connection between the cursor and the previous route should appear. In general Cntl-Nroutes from the cursor to the selection.There are a number of commands to set parameters and otherwise interact with the Irouter.These commands have the general form:iroutesubcommand [arguments]For a list of subcommands and a short description of each, type:iroute helpUsage information on a subcommand can be obtained by typing:iroute help [subcommand]As with Magic in general, unique abbreviations of subcommands and most of their argumentsare permitted. Case is generally ignored.–2–Magic Tutorial #10: The Interactive Router September 26, 20013 :Undo and Cntl-CAs with other Magic commands, the results of :iroute can be undone with :undo, and if theIrouter is taking too long it can be interrupted with Cntl-C. This makes it easy to refine the resultsof the Irouter by trial and error. If you don’t like the results of a route, undo it, tweak the Irouterparameters or hints you are using and try again. If the Irouter is taking too long, you can very likelyspeed things up by interrupting it, resetting performance related parameters, and trying again. Thedetails of parameters and hints are described later in this document.4 More about Making Connections—‘:iroute route’Start points for routes can be specified via the cursor, labels, or coordinates. Destination areas canbe specified via the box, labels, coordinates or the selection. In addition start and destination layerscan be specified explicitly. For the syntax of all these options type:iroute help routeWhen a start point lies on top of existing geometry it is assumed that a connection to thatmaterial is desired. If this is not the case, the desired starting layer must be explicitly specified.When routing to the selection it is assumed that connection to the selected material is desired.By default, routes to the box may terminate on any active route layer. If you are having troubleconnecting to a large region, it may be because the connection point or area is too far in the interiorof the region. Try moving it toward the edge. (Alternately see the discussion of the penetrationparameter in the wizard section below.)5 HintsMagic has three built-in layers for graphical control of the Irouter, fence (f), magnet (mag), androtate (r). These layers can be painted and erased just like other Magic layers. The effect each hason the Irouter is described below.5.1 The Fence LayerThe Irouter won’t cross fence boundaries. Thus the fence layer is useful both for carving outrouting-regions and for blocking routing in given areas. It is frequently useful to indicate the broadpath of one or a series of routes with fence. In addition to guiding the route, the use of fences cangreatly speed up the router by limiting the search.5.2 The Magnet LayerMagnets attract the route. They can be used to pull routes in a given direction, e.g., towards oneedge of a channel. Over use of magnets can make routing slow. In particular magnets that are longand far away from the actual route can cause performance problems. (If you are having problemswith magnets and performance, see also the discussion of the penalty parameter in the wizardsection below.)–3–September 26, 2001 Magic Tutorial #10: The Interactive Router5.3 The Rotate LayerThe Irouter associates different weights with horizontal and vertical routes (see the layer-parametersection below). This is so that a preferred routing direction can be established for each layer. Whentwo good route-layers are available (as in a two-layer-metal process) interference between routescan be minimized by assigning opposite preferred directions to the layers.The rotate layer locally inverts the preferred directions. An example use of the rotate layermight involve an L-shaped


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UCD EEC 116 - The Interactive Router

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