About CompactPCI
Introduction
The 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 popularised 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:
Standard Eurocard dimensions (complies with IEEE 1101 mechanical standards)
High density 2mm Pin-and-Socket connectors (IEC approved and Bellcore qualified)
Vertical card orientation for good cooling
Positive card retention
Excellent shock and vibration characteristics
Metal front panel
User I/O connections on front or rear of module
Standard chassis available from many suppliers
Uses standard PCI silicon manufactured in large volumes
Staged power pins for Hot Swap capability
Eight
slots in basic configuration. Easily expanded with Bridge Chips
With the move from the parallel PCI bus to the serial busses, like PCIExpress, StarFabric, RapidIO, subsequent specifications were added to the CompactPCI family. For instance, 2.16 CompactPCI Packet Switching Backplane specification overlays a packet based switching architecture on top of CompactPCI to create an Embedded System Area Network. It provides a redundant, switched 10/100/1000 Ethernet network within a Compact PCI chassis providing connectivity between all slots using a star topology. It is intended to coexist with 64 bit CompactPCI and H.110. Special slot(s) for active switching fabric element(s), which may be redundant, are also specified.
The CompactPCI Express
Specification, denoted EXP.0, brings the
PCI Express technology to the CompactPCI form factor,
while maintaining compatibility with CompactPCI hardware
and software. The specification defines the connector,
electrical, and mechanical requirements of 3U/6U System
Boards, Peripheral Boards, Switch Boards, and Backplanes
and leverages the Advanced Differential Fabric (ADF)
connector used by AdvantedTCA to carry the PCI Express
Signals. It maintains hardware compatibility with CompactPCI
by allowing backplanes to have CompactPCI slots
as well as Hybrid Slots, which support CompactPCI, PXI,
and Compact PCI Express peripheral boards.
The specification defines the system slot and board to have up
to 24 lanes and up to four links of PCI Express for up to 6 Gigabytes/second
system bandwidth per direction. Type 1 peripheral
slots and boards can have up to 16 lanes of PCI Express
for up to 4 Gigabytes/second bandwidth per direction and
Type 2 peripheral slots can have up to 8 lanes of PCI Express
for up to 2 Gigabytes/second bandwidth per direction. CompactPCI Express provides migration path
for customers who use the highly successful
CompactPCI form factor but want the added
performance of PCI Express.
The CompactPCI Connector
At the heart
of CompactPCI is a gas tight, high density pin-and-socket connector which meets
the IEC-1076 international standard.
Its low inductance and controlled impedance make it ideal for PCI signalling.
This 2-millimetre "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 ground pins
ensures adequate shielding and grounding for low ground bounce and 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 desktop 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.
Connector Definitions
3U
CompactPCI processor boards use a single 220 pin connector for all power, ground,
and all 32 and 64 bit PCI signals. This connector consists of two halves - the
lower half (110 pins) is called J1 and the upper half (also 110 pins) is called
J2. 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 single 110-pin connector (J1). 32
bit boards and 64 bit boards can be intermixed and plugged into a single 64-bit
backplane.
6U
boards can have up to three additional connectors with a total of 315 pins.
These are also 2mm style. These optional connectors can be used for a variety of
purposes. They can be used as a bridge to other buses like VME or ISA in hybrid
backplanes. 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. PICMG is developing "recommended practices" with
defined pinouts for bridging to VME-64 and telephony buses like SCSA and HMVIP.
These
connectors, in conjunction with commercially available PCI-PCI bridge chips, can
also be used to extend the CompactPCI bus in 8 slot increments. In this manner a
CompactPCI system with 16, 24 or even 32 slots can easily be fabricated.
The connectors can also be used for rear panel I/O in a manner similar to VME.
This approach, popular in the telecommunications industry, brings I/O wiring out
the rear of the chassis. Eliminating front panel wiring can reduce the time
required to replace a module in critical applications. The IEEE 1101.11 draft
standard for rear panel I/O provides a standard method for doing this, and works
well with CompactPCI.
The complete specifications can be obtained from PICMG Europe by using our order form.