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VUTRAX Technical SupportVUTRAX SOFTWARE ADVICE NOTICE 173 - 8 Dec 1997 VUTRAX 11 onwards Advice on Optimising Signal Networks on double sided strips of components (e.g. SIMMs) Background: VUTRAX offers numerous means of automatically optimising the connection network of a signal. These include 'Network' - (spanning tree - shortest routes), ECL sequenced, Various styles of sequential sweep across the board, Local swapping, and suppression (connections accepted in component order). After placement the DRAFT 'Optimise' should be used to re-sequence 'network' optimised signals. To re-sequence other types you need to [Analyse Placement] and generate a new rats nest. All forms of automatic optimisation use both sides of the board freely to minimise interconnection length. If the optimisation is not as you wish, a limited number of signals is most easily modified using [Disconnect Path] and [Reconnected Path] from (Reconnect). Optimising Strips of components Designs with SM devices on both sides of a board sometimes require commonly interconnected signals to run to a board's extremity before 'vias' take them through for connecting the underside components. An example is a SIMM memory module. We suggest here a technique to obtain signal optimisation in the appropriate style. Instead of initially placing components on front and back, place all component side components as normal but then place all solder side components in a continuing strip off the edge of the board, as though you had opened out the board so that (nominally) component and solder sides are side by side. Now run Optimse on the design. The effect is to ensure that connections for the top/bottom connections run from one edge. Flip each solder side component and place it behind the component side design. So that this arrangements does not get subsequently destroyed by the AUTOTRAK or VUROUTE router pre-route optimiser, clear the Network Optimisation and Optimisation Required markers for all signals. The design can now be autorouted normally. 3rd party routers may ignore optimisation limits unless you explicitly instruct the router otherwise. Circulation: On Enquiries about optimisation techniques. Internet Site. |