|Baumeister Mediasoft Engineering|
The Bartels Autorouter® was the first PC based protected mode rip-up/retry router. It is still the only one with selective Rip-Up/Cleanup/Backtracking. Previous versions were known as Superoute of which thousands of licenses were sold worldwide. Superoute modules were also modified by some source code OEM customers. Routers sold today under the name Superoute no longer represent Bartels latest routing technology.
Bartels is the original source for all of the OEM versions resulting from more than 15 OEM contracts. The latest Bartels Autorouter® version is integrated in the Bartels AutoEngineer® CAD/CAE system.
The router supports gridless placement of pads, obstacles and traces, cell based routing grid, routing with one or multiple cells in width to existing on-grid or off-grid pads and on-grid or off-grid traces. The off-grid feature is a combination of grid-based and gridless routing technologies and does off-grid routing of traces even in a cell-based environment, making it the ideal combination between cell-based and shape-based technologies.
Integrated with the BAE schematic and PCB rule system, the Bartels AutoEngineer supports automatic assignment of net classes based on library part/pin classifications and schematic tags to the actual design. Together with rules assigned to PCB areas, this allows for board design with EMC (Electromagnetic Compatibility) rules application.
Increased use of SMT fine pitch parts has created a demand for a flexible grid routing technology. The previous versions of the Bartels AutoEngineer used the following data representation:
In this case floating point coordinates permit what is called a "gridless" (shape/contour) representation. This database supports true floating point polygons/polylines including arcs for all data including prerouted fixed traces, however, with the exception of currently routed traces. The router can connect to off-grid junction points, including pins and fixed traces.
With the introduction of the sub-grid mode, the on-grid limit for routed traces was relaxed to half-grid (one-half) shifted traces, thus permitting proper handling of fine pitch SMT. However, this mode requires additional matrix memory and more computing time.
Competing products claiming to be "gridless" choose a multi-way (mostly four-way) geometrical tree approach which ends up in rectangular leafs. The advantage of this data representation is that rectangular data may indeed be represented with high resolution and routing is fast if trace and corner density is low. However, for high-density boards it requires even more memory than a matrix-based approach, and access time for allocation checks at certain board positions can increase excessively. The greatest pitfall, however, is the lack of efficient facilities for joining neighbouring rectangles, thus layout quality in true gridless mode often deteriorates dramatically, with 100% routing results becoming exceptional. This is especially true for non-rectangular (e.g., polygon) obstacles and 45 degree routing.
Our solution is to keep the matrix at the lowest possible density for strategic routing purposes, and to do the final artwork on a gridless database.
The Bartels Autorouter V6.0 maintains a floating point database for routed traces parallel to the integer/matrix representation (dual database). The matrix allows for efficient routing and rip-up/retry with high quality results even for highest trace and/or ratsnet density. The floating point contour/shape routing database results in efficient board space usage by finding off-grid SMT channels and high quality SMT pad connections including long distance off-grid routing where required and/or applicable. The dual database combines the advantages of both concepts, thus giving significant improvement over both pure matrix and pure shape-based routing. The strategic trace routing is done via the matrix, thus both the advanced Lee algorithm which guarantees to find the least cost optimum way for a single trace, and the Bartels RipUp and CleanUp algorithms which detect optimum traces for rip-up and cleanup, can be used together with a non-rectangular shape-based database.
The dual database is an open end development. One of the next steps will be simultaneous maintenance of multiple routing matrices to reach even higher quality on mixed analog/digital boards. Further developments could yield the selective placement adjustment for certain parts to combine and thus gain additional trace channels.
The Bartels Autorouter V6.0 is also called the Neural Router because it may be combined with the Bartels Rule System. The Rule System applies one or more rules to system objects such as parts or traces. The rules are defined using a language similar to Prolog, however, with special operators to find not only all possible, but also optimum solutions to design-specific rule system queries or output requests.
The rules may be defined and assigned to individual items such as parts, nets, or traces as well as for the overall system, e.g., for cost factor and routing strategy control.
As the Rule System uses a novel neural net approach to focus the rule evaluation on the probably best path, the Bartels AutoEngineer combined with the Rule System is called the Bartels Neural Autorouter™.
The Bartels Autorouter V6.0 implements the pin/gate/group swap within the router depending on the routing results. If enabled, this feature permits routing of even the most complex boards, because the router gains an additional degree of freedom. The swaps done by the Autorouter are reported by the output interface and requests for correlating the schematic plan are automatically stored with the design.
Together with the introduction of the pin/gate/group swaps, a part-oriented input interface was implemented to permit placement optimizations by the router in future versions. The interface now maintains an additional attribute field (trace/via ident code) to support rather specific definitions such as traces on part level, a BAE-specific feature widely used for defining printed inductors.
A documented interactive routing functions interface is provided to implement the interactive single net/part routing features through the standard interface (used by the Neural Autorouter module).
In addition to standard negative power planes and copper and copper pour areas, the Autorouter now also supports split hierarchical negative power planes.
|Baumeister Mediasoft Engineering, Clontarf, Dublin 3, D03 HA22, Ireland
© 2021 Manfred Baumeister