OpenVpx Switch backplane

Supported Switched/Mesh Fabrics by Mercury Systems – Part 1

The SMP Engineering group at Mercury Systems has worked tirelessly on development and innovation to offer our customers multiple choices for their present and future needs. Since authoring the OpenVPX™ (VITA 65) standard, it has opened the door to customers seeking answers and/or solutions to many of the issues they encounter when designing their systems. First, let’s take a look at what OpenVPX offers us.

OpenVPX builds on the module-centric VPX specifications by providing a nomenclature of planes and profiles to enable system integrators, module designers, and backplane providers to effectively describe and define aspects and characteristics of a system. OpenVPX addresses major system interoperability issues while allowing for flexibility within the system, as enabled by its planes and flexible module profiles featuring user-defined I/O. By following a system-centric approach and defining a number of standard system topologies, OpenVPX enables interoperable off-the-shelf modules and development platforms within the VPX marketplace. The standard has provisions for both 6U and 3U platforms, and high speed serial switched fabric technologies such as PCIE, RapidIO, Infiniband, 10 Gigabit and 40 Gigabit Ethernet.

OpenVPX profiles make it easy to build development systems with compatible components. Deployable systems will always have system issues that need to be addressed, such as I/O, custom backplanes, power, and cooling. SMP engineers not only understand these issues, we have also solved both integration and system-level problems and delivered integrated system solutions to our customers.

OpenVPX Benefits

  • Promotes interoperability and vendor choice
  • Provides specific design profiles that vendors can design to and integrators can specify as requirements
  • Reduces integration issues resulting in faster development & deployment time
  • Higher board volumes –> Economies of scale
  • Industry leading bandwidth and density
  • Higher velocity of technology upgrades
  • Will support higher backplane signaling speeds as technology matures

Now let’s look at the switched fabrics and their supported backplane topologies with OpenVPX platforms.

Types of Backplane Topologies

  • Centralized switching
  • A set of peer payload boards connected by switch fabric boards
  • Single or dual star topology for multiple path routing and potential redundancy
  • Provides system management function
  • Mesh Fabric
  • A set of peer payload cards connected in a full or partial mesh
  • Useful for small slot count systems as it avoids dedicated switch slots
  • Larger slot count systems require switching logic on each payload card
  • Host / slave
  • Typically comprise a master host board with several slave boards linked by PCIe
  • Allows an SBC to have greatly expanded capabilities without complexity of a general switching fabric

Planes and Profiles

Planes: Multiple levels of communication; Bottom to top

  • Utility Plane – Power pins and various utility signals
    • NVMRO (Non-Volatile Memory Read Only)
    • SYS_CLK (System Clock), REF_CLK (Reference Clock), AUX_CLK (Auxiliary Clock)
    • SYSRESET (System reset, including “maskable reset”), POWER
  • Management Plane (mp)
    • Low-power
    • Defined by VITA 46.0 and 46.11
    • Prognosticates/diagnoses problems
    • Can control module power
    • IPMC
  • Control Plane (cp)
    • Reliable, packet-based communication that carries information necessary to establish and control the network
    • Application control, exploitation data
    • Typically Gigabit Ethernet or less
  • Data Plane (dp)
    • High-throughput, predictable data movement without interfering with other traffic
    • Examples: Serial RapidIO, PCI Express, CX3(Connect-3), Infiniband, Ethernet: 10GB or 40GB, Infiniband: 56 GB
  • Expansion Plane (ep)
    • Tightly coupled groups of boards and I/O
    • Typically VME bridging or PCI Express

Profiles: Three types

  • Slot Profile
    • A physical mapping of ports onto a slot’s backplane connectors
    • Uses notions of pipes and planes:
      • The term “pipe” is used to define the number of bidirectional differential serial pairs that are grouped together to form a logical data channel.
    • Does not specify actual protocols conveyed over the backplane
  • Backplane Profile
    • A physical specification of a backplane
    • Specifies the number and type of slot profiles
    • Defines the topology of channels and buses that interconnect the slots
  • Module Profile
    • Extends a slot profile by mapping protocols to a module’s ports
    • Includes thermal, power and mechanical requirements
    • Provides a first order check of compatibility between modules

Next time we will dive deeper into what capabilities are available, how the systems can match your needs, and where Mercury Systems can assist its customers.