VME Technology
Introduction
VME Technology is a favorite choice as an embedded systems architecture for critical embedded systems. Many current users have taken advantage of the long life cycle of VME products and have refreshed their product lines with the vast selection of VME products on the market. New projects are leveraging the advancements in VME technology with an eye on performance and the life cycle advantages of VME.
The VME technology family of specification has grown significantly since its inception. VMEbus has expanded from the original family of the core VME32 parallel bus, a VME Subsystem Bus, and a VME serial interconnect to today’s broad family of complementary state-of-the art specification.
New projects are leveraging these advancements in VME Technology, capturing the benefits of performance and life cycle advantages. Today’s VME Technology includes:
- Parallel bus performance of over 300 MB/s using VME 2eSST, with more bandwidth performance on the near horizon.
- Serial switch fabric interconnects in XMC, VXS, VPX and new standards that include Gigabit Ethernet, PCI Express, RapidIO, and InniBand.
- Specifications to help standardize environmental criteria, digitization of radio frequency data, reliability prediction, and other topics important to electronic systems design.
With its rich heritage and bright future, VME Technology has found an indispensable place in what are termed Critical Embedded Systems. These are the systems that must be “able” in many dimensions: dependable, supportable, congurable, reliable, serviceable, . . .
These systems must operate flawlessly to protect life, property, equipment, and the environment – and to do that they rely on the durable products of today and tomorrow using VME Technology.
Several system management specifications have also been ratfied that make the development of VME systems easier with more robust system management. Proposals continue to be submitted and considered for addition to the VME Technology family to improve VME’s utilization in complex systems.
The VME Standards Organization (VSO) has ratified over thirty VMEbus Technology supporting standards, with many more in working group status at this time. These standards support the continued evolution of the core VMEbus Technology to ensure a solid foundation for the future.
VME Technology Roadmap
The VME Technology roadmap helps direct users through the various VME related options and encourage user participation in future specification development.
The roadmap consists of major specifications as the base of VME technology, the foundation upon which solutions may be built. New emerging standards build on the legacy of VME Technology compatibility. Switch fabric and system management specifications are additional layers that build upon the core specifcations.
Each of these standards adds progressively more capability and per formance to the VMEbus Technology core. New products, from many suppliers, are emerging that leverage the evolutionary changes in technology.
Backplane Solutions
VME32 is where everything started in October 1981. The original specification was sponsored by the VMEbus Manufacturer’s Group, now VITA, and eventually standardized as IEEE 1014 and IEC 821. VMEbus established a framework for 8-, 16- and 32-bit parallel-bus computer architectures that could implement single and multiprocessor systems. The VMEbus includes four basic sub-buses: (1) data transfer bus, (2) priority interrupt bus, (3) arbitration bus, and (4) utility bus. Other architectures, with other sub-buses are possible within this VME framework.
In 1994, VME64 was formally approved by ANSI as ANSI/VITA 1-1994, incorporating all the features of VME32 plus adding support for 64-bit transfers.
VME32/VME64 compatible products continue to be deployed in numerous applications throughout the world. The VME Technology roadmap is committed to a legacy of backward compatibility as technology advances.
VME64x (ANSI/VITA 1.1) is an extension of the VME64 standard. It de nes a set of features that can be added to VME32 and VME64 boards, backplanes and subracks. These features include a 160 pin P1 and P2 connector, a P0 connector, geographical addressing, voltages pins for 3.3V, a test and maintenance bus, EMI, ESD, and front panel keying per IEEE 1101.10.
The 160 pin connectors greatly increased the bandwidth and I/O capability of VMEbus.
ANSI/VITA 1.7 added support for an increased current DIN connector that doubled the maximum wattage capacity of a VME module.
VME64x is a commonly used in many applications today. It also shares in the backward compatible legacy of VME Technology.
VME 2eSST (ANSI/VITA 1.5) extends performance by adding dual edge, source synchronous data transfer (2eSST) capability that allows sustained data transfers in excess of 300MB/ sec. During its data phases, 2eSST is a source synchronous protocol. No acknowledgment is expected from the receiver of the data. Hence, the theoretical performance of a 2eSST VMEbus system is limited only by the skew between receiver and transmitter of data.
Concepts exist to enhance 2eSST performance to over 1GB/sec while remaining backward compatible with earlier VMEbus implementations.
Gigabit Ethernet on VME64x (ANSI/VITA 31.1) adds GigE to backplanes via a P0 connector as defined in VME64x. This is the first generation of serial switched fabric solutions implemented in VMEbus backplanes. This implementation works well with VME32, VME64 and 2eSST configurations.
VXS (VME Switched Serial) combines the event-driven parallel VMEbus with enhancement s to suppor t switch fabrics over a new P0 connection. VXS maintains backward compatibility with existing backplanes that do not have a conflicting P0 scheme. Several fabric protocols are mapped out for VXS including, 10 Gigabit Ethernet, PCI Express, Serial RapidIO and Infiniband. VME’s parallel bus architecture provides bus control and maintenance data, handling everything from single byte transactions to +300MB/s block data transfers. Combining this in various ways with the switch fabric technologies for multi-point, high-speed data transfers creates choices for embedded computing designs of all types.
VPX standards establish a new direction for the next revolution in bus boards. It breaks out from the traditional connector scheme of VMEbus to merge the latest in connector and packaging technology with the latest in bus and serial fabric technology. VPX combines best-in-class technologies to assure a very long technology cycle similar to that of the original VMEbus solutions. Traditional parallel VMEbus will continue to be supported by VPX through bridging schemes that assure a solid migration pathway.
REDI defines a general mechanical design implementation for Eurocards such as VMEbus and VPX that enhances thermal performance and structural integrity as well as providing for Two Level Maintenance (2LM) compatibility.
REDI gives an overview of the associated plug-in units for air-cooling, conduction cooling, and liquid cooling applications. The REDI family of standards defines applicable detailed dimensions of key plug-in unit and sub-rack interfaces.
Mezzanine Cards
Many mezzanine card specifications have emerged out of the work of VITA. These cards provide increased Flexibility and functionality to VME technology.
In particular, the technologists have expanded on the PCI Mezzanine Card (PMC) standard in many way that improve their compatibility with VME technology.
PrPMC (ANSI/VITA 32) adds the capability of bus mastership to the PMC to enable processor cards to operate as master/host modules. PCI-X bus support is added in ANSI/VITA 39.
XMC (ANSI/VITA 42.x) opens the specification cation to support various serial buses such as PCI Express, Serial RapidIO, and other high speed serial interfaces while still offering backwards compatibility with PMC.
FMC (ANSI/VITA 57) is similar in size to PMC but is designed to connect to programmable devices such as FPGAs to allow a standard way to route user I/O to the front panel.
Reliability
The Reliability Prediction Community of Practice is a product of a collaborative effort by a working group in VITA, comprised of representatives from electronics suppliers, system integrator companies, and the Department of Defense (DoD). This working group has announced their first results at forming a community of practice document that provides an electronics failure rate prediction methodology and self-assessment standard.
Failure rate predictions have been utilized by logistics and systems engineers for a myriad of purposes, including reliability analysis, cost trade studies, availability analysis, spares planning, redundancies modeling, scheduled maintenance planning, product warranties and guarantees.
The Reliability Prediction Community was formed to investigate and develop an industry standard to address electronics failure rate prediction. Where applicable, this standard provides adjustment factors to existing standards.
VME – The Right Choice
The original VMEbus Technology specifications remains a foundation upon which evolutionary changes are made. The foundation continues to be a valid base that is compatible with new VMEbus technology. Products based on earlier generations of the VMEbus technology family remain valid and continue to be interoperable with the new developments.
VME is a Versatile, Mainstream, Evolutionary solution to your computing needs. Be sure to visit www.vita.com for the latest developments in VME Technology.
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