The newest standard for PCI-based industrial computers is called CompactPCI. It is electrically a superset of desktop PCI with a different physical form factor. CompactPCI utilizes the Eurocard form factor popularized by the VME bus.
Defined for both 3U (100mm by 160 mm) and 6U (160mm by 233 mm) card sizes, CompactPCI has the following features:
At the heart of CompactPCI is a new, high density pin-and-socket connector. This connector meets the IEC-1076 international standard and is manufactured by multiple vendors, including AMP, Framatome, Burndy, and ERNI. This 2 millimeter "Hard Metric" connector has 47 rows of 5 pins per row, with a total of 220 pins (15 pins are lost to the keying area). An additional external metal shield is also used. The large number of pins ensures adequate shielding and grounding for reliable operation in noisy environments. This connector's controlled impedance minimizes unwanted signal reflections and enables CompactPCI systems to have eight slots, as compared to the dekstop PC's four. This can easily be expanded with PCI bridge chips, available from a number of manufacturers. Staged power and ground pins are specified for future hot swap capability.
3U CompactPCI boards use a single 220 pin connector for all power, ground, and all 32 and 64 bit PCI signals. This connector is called J1. Twenty pins are reserved for future use. Backplanes use male (pin) connectors and plug-in boards use female (socket) connectors. Plug in boards that only perform 32 bit transfers can use a smaller 110 pin connector. 32 bit boards and 64 bit boards can be intermixed and plugged into a single 64 bit backplane.
6U boards have an additional 220 pin connector. This connector is intentionally undefined at this time. It is used for a variety of purposes. It can be used as a bridge to other buses like VME or ISA. These "hybrid" backplanes use CompactPCI for the processor and high speed peripheral section and one of these industrial buses for an I/O expansion section.
The connector, in conjuncion with a PCI-PCI bridge chip, can be used to extend the CompactPCI bus by another 8 slots. In this manner a CompactPCI system with 16 slots can easily be fabricated.
The connector can also be used for rear panel I/O in a manner similar to VME. This approach, popular in the telecommunications industry, brings all wiring out the rear of the chassis. Eliminating front panel wiring can reduce the time required to replace a module in critical applications.
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CompactPCI Short Form Specification
The CompactPCI Short Form Specification is available in Adobe Acrobat
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Click here to download the CompactPCI Short Form Specification (114K)
The complete specification can be obtained from the PCI Industrial Computer Manufacturers Group (PICMG). They can be reached at 617-224-1100.