Avoiding The Barriers For Multi-Board Systems Design Development

Designing electronic systems that comprise multiple interacting boards, connectors and cables requires a multi-discipline team collaboration to effectively manage design complexity for optimum product performance and reliability. Multi-board systems may comprise two boards or up to hundreds of boards, packing a cabinet or rack, with interconnected connectors and/or cables. Since the hardware functionality is now distributed across multiple boards, the system integrator must determine the connections that need to be made between each board, and to external interfaces. As design complexity rises, there could be tens of thousands of connections.

Today, systems designers still rely on desktop drawing programs, spreadsheet editors, and document editors. Once the system has been fully conceptualized, the systems designer can begin to define a logical view of the system interconnect. But this approach is not ideal, with the ever expanding complexity and speed of products, and the decreasing footprint for the hardware. The sheer number of hours required to define connector pin assignments and verify connectivity is staggering. And regardless of project design reviews, errors get missed, sometimes with devastating financial consequences.

Once the functionality of each PCB and their interconnections has been defined, the design goes to the PCB and cable design groups. Unfortunately, the interconnectivity data must be manually re-entered, introducing the potential for error. From the time of hardware conceptual design until that production unit heads out the door, there will almost certainly be changes to the design. Some of these changes are trivial from the system level perspective, such as a screw size change, or a different bypass capacitor manufacturer. But other changes can critically affect the system design – in particular, the connections and high-pin count connectors between boards.

Re-defining the connectors among the affected boards is an enormous task and ripe for errors since it is a substantial manual operation with a spreadsheet. Once the connectors are re-defined, the data must be sent to each of the PCB design teams to modify the designs. Since the data is not integrated with the systems designer’s spreadsheet, more manual re-entry is required, resulting in more chances for errors and risk of re-spins to “get it right.” Current design tools are being taxed to the point of becoming unviable – particularly as design complexity increases.

Critical systems design flow from concept to manufacture.

The lack of an integrated solution is the major problem. When inevitable changes occur, each of the affected connectors must be thoroughly checked and rechecked. This is not just at one level, but at each level where data is manually managed. This means checking two or more places each time a change is made. Without an integrated connection between the system design and the PCB design, hours are lost, errors are common, and projects get delayed.

Multi-board systems design requirements
Many multi-board systems have external connectivity, input/output signals, data, power and ground, combinations of both, or even more complex combinations if the multi-board system is part of a much larger system, or system-of-systems. What’s needed is an efficient, documented, intelligent and manageable process for communicating such logical connectivity to other design teams and/or systems. Another requirement: a solution that can receive logical connectivity and signal information to ensure external connector selection and signal/pin assignment is made correctly and modified as necessary.

In addition to external multi-board system connectivity communication, design teams need an environment to support concurrent collaboration. This environment would allow multiple systems designers to work on all design elements simultaneously as multiple hardware engineers are working on the logical and physical PCB design environment, including multi-project work-in-progress revision control and management. Any changes would be communicated through the work-in-progress design management hub, ensuring the whole process is kept in sync and nobody is using the wrong revision/version of design IP.

Once logical boards and PCB design associations are created at the system level, the system designers can synchronize the content of the logical boards and associated PCB schematics using bi-directional forward and back annotation. System level information passed to the PCB schematic comprises the system connectors and system level blocks. Board designers can then access these blocks and define the underlying logic on the schematic for each specific function of the system.

Ideally, the software synchronizes and tracks all changes between each board and its content, connectivity between the boards, and pin-to-pin relationships between connectors. The process provides up-to-date status immediately to all the users involved in the systems design process. Thus, any change made anywhere within the design stream is propagated forward and backward so that all staff working on the project have the same up-to-date data. Furthermore, this same data is propagated to the PCB design flow, ensuring that no manual errors are introduced.

A viable methodology for multi-board systems design efficiency and collaboration
Hardware system design complexity is immense and current methods for managing this have limitations in both capacity and process. To compete in today’s economy, current systems design methods take too long, introduce too many errors from manual data entry, and require re-entering the same data at multiple points in the design process. The current methodology incurs errors based on time, money and lost opportunity. Failure to maintain the integrity of even a single interconnection could result in delay, thousands of dollars to resolve, and perhaps even a product recall. To combat these possibilities, some manufacturers have built in “fail safe” precautions, but these add cost to every unit.

Mentor Graphics’ new Xpedition multi-board systems design flow enables seamless concurrent multi-discipline team collaboration to manage today’s increasing system complexity.

The PCB design realm has seen huge advances in the last decade. What is needed at the multi-board system level is a solution that automates the enormous connection management problem, facilitates easy system and logical design, and integrates seamlessly with the PCB design flow while managing team, design and library data at each level of the design hierarchy. Mentor Graphics just introduced its Xpedition multi-board systems design methodology for multi-discipline team collaboration. It is a single integrated environment that enables multi-board systems design, including logical design, partitioning and connector and wiring management. Now, hardware design, from multi-board system specification to completed PCBs and cables can be handled with one integrated flow.