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Reducing Design Cycle Times
December 31, 1969 |Estimated reading time: 6 minutes
In today’s competitive electronics industry, getting to market ahead of the competition can mean the difference between a successful product and one that misses its market window. Design cycle time plays a big part in determining a product launch schedule and the PCB layout portion of this process often is called upon to make up for early design phase schedule slips. One designer and one computer at a time can be a limiting factor.
By John Isaac, Mentor Graphics
Traditionally, designers are pulled in from other projects to assist with meeting deadlines, usually by adopting shift-work routines or physically splitting the design into multiple pieces. Both methods incur significant overhead costs that tend to negate the advantage of design collaboration. Partitioning the design into pieces and having designers work separately on each piece can help improve the situation. But putting that design database back together is a tedious and error-prone task.
PCB Design Solutions
There are technologies available that can change the way PCBs are designed. One solution enables PCB designers and multiple computer processors to work on a single design database simultaneously. This parallel-design technology requires a design session manager (server) and multiple design clients in a LAN- or WAN-networked environment (Figure 1). The primary activity of the server is to receive updated requests from each client, check the request to ensure that no design rule violations are made, and then synchronize each client and a common database with updates. Each client has its own dedicated processor and memory and views the entire design. They also can witness the edits from other clients as the server processes them. The design database can be stored anywhere on the network.
Figure 1. Parallel design client-server network.
This parallel-design-solution architecture does not require designers to partition the design in any manner. This makes it a true real-time collaboration environment, eliminating problems associated with partition boundaries while reducing the total time to complete the design. Users claim that it enables them to cut design cycle times by 40-70%, depending on the number of designers and the nature of the board. Location means little because designers can be in the same office or dispersed globally.
To begin a design session, the board design is loaded onto the server by any member of the design team. As clients join the session, they provide a name to identify themselves to the other users. In addition, the current state of the layout design is downloaded automatically onto the client’s local desktop computer. By working on the design locally, designers can use the processing power and memory of their own workstation, yet still view the entire design and witness edits from other clients as the server processes them in real time. Clients also can join or leave the session at any time.
A Video Game for Designers
The technology is similar to a video game, where each designer can view the actions of others in real time. When a team member selects an object, that event is captured and sent to the server as an update request. For example, moving a component from point A to point B constitutes an event that begins with the selection of the part and ends by a mouse click indicating the new location. The edited event is sent to the server as a transaction describing what should be deleted and what should be added. The server performs DRC on the event and, if it passes, accepts the event, updates the central database, and communicates the change to all the other clients.
There are, however, potential conflicts that can occur when multiple designers work on one project. For instance, two designers may be performing routing in the same area, and these routes may interfere with one another. To resolve this potential conflict, there are a set of rules, turf allocations, and client-priority setting criteria. Methods used include:
Figure 2. Force fields identify individual team members to avoid design conflicts.
- Simultaneous object/action collisions - Design changes are automatically resolved through selection priority based on first-in-first-out (FIFO) principles. When a designer selects an object for editing, it is locked to all other clients.
- Protected areas - Designers may define a region to be protected, preventing others from making edits in that area.
- Conflict avoidance - Force fields can be displayed around the cursor to indicate the whereabouts of each client and prevent designers from working too close to each other. The more a designer works in an area the larger their force field (Figure 2). As they move to a new location the force field reduces.
Current technologies tout the ability to allow up to 15 designers to operate simultaneously. However, user experience suggests that, depending on the nature and complexity of the board, two to five designers provide the optimum design cycle time reduction. Other possible benefits include:
Figure 3. Reducing auto-routing times depends on the number of clients and the nature of the board.
- Resource management - The CAD manager can use resources within the team efficiently. If a designer has time, he or she can join the critical design project immediately, perform routing or placement, and leave the project when necessary.
- Specialists - If a design has a mixture of digital, analog, and RF technology, specialists in each of these disciplines can simultaneously design that specific portion of the board. Using this parallel design methodology, instead of a serial one, can further reduce cycle times.
Multiple Auto-routers
The second application of the design methodology is simultaneous auto-routing on multiple processors. Here, multiple clients (up to 15) can attack auto-routing of a high-density, complex board. This can result in a 5-10× reduction in execution time, depending on the nature of the board and the number of processors. In effect, this reduces an auto-route job that would run for several days to an overnight job (Figure 3).
The auto-route application works similarly to the layout application. A user with an un-routed design database searches the network for available computers and captures those resources. The server then executes the routing job on captured computers and manages the inter-client communications and central database updating. The server handles all conflicts and scheduling of interconnects.
Execution on multiple clients is transparent to the user once they secure client machines and begin the job. Routing passes are set up identical to those established for a single processor. Results during execution are displayed on the server. Similar to execution on a single processor, the job can be halted and restarted. If the WAN or LAN should fail during execution, current results are saved and the job can be restarted. Auto-routing runs faster, and users spend less time waiting for results. Another benefit is not as obvious. Designers often take several passes at a design with variations in component placement or high-speed constraints. By having an auto-router that can run in a fraction of the time, designers can take more passes at the design, pick the best scenario, and proceed to the final design.
Conclusion
Pressure to design higher-performance, lower-cost products in shorter times requires new design technologies and tools. Aggressive time-to-market pressures will not ease up, so future design methodology applications must extend in use beyond the placement and routing domain, and into all aspects of the design process.
John Issac, director of market development, Systems Design Division, Mentor Graphics Corporation, may be contacted at (720) 494-1270; john_isaac@mentor.com.