Backplane databuses are a dying breed in advanced military avionics

Designers of advanced U.S. military avionics are starting to turn away from the venerable parallel backplane data bus computing architecture in favor of more advanced approaches that rely on high-speed serial databuses and switched networks.

Sep 1st, 2002

by John Keller

OWEGO, N.Y. - Designers of advanced U.S. military avionics are starting to turn away from the venerable parallel backplane data bus computing architecture in favor of more advanced approaches that rely on high-speed serial databuses and switched networks.

Two of the most visible examples of this design trend involve the SP-103 avionics processor architecture from Lockheed Martin Systems Integration in Owego, N.Y., which is part of the design for the future Lockheed Martin F-16 Block 60 jet fighter and F-35 Joint Strike Fighter (JSF).

On those two aircraft, the design stage is set for a switch from the VME data bus to future-generation high-speed serial databuses and switched-network processor fabrics, says Timothy E. Malia, manager avionics product development at Lockheed Martin-Owego.

"In the F-16 Block 60 and in the JSF, we are cutting the cords to VME," Malia says. "Fibre Channel is the switched-network fabric for the board-to-board, and system-to-system interconnect. In the future, RapidIO will be the chip-to-chip interconnect."

In the foreseeable future, Malia says Fibre Channel is the best choice for interconnecting boards and subsystems, while RapidIO will be best for interconnecting integrated circuits. "One fabric can't cover the entire aircraft," Malia says.

Today's VME-based avionics architectures move data among printed circuit boards inside separate boxes over the VME parallel backplane data bus. Tomorrow's Fibre Channel and RapidIO-based avionics architectures will consist basically of boxes connected by switches to sensors, Malia explains.

This architecture will continue using printed circuit boards inside avionics boxes, but will dispense with the parallel backplane. Malia says Lockheed Martin designers most likely will continue to use the VME printed circuit board form factor, however.

Malia says Lockheed Martin's choice of the RapidIO chip-to-chip high-speed interconnect revolves around the Motorola PowerPC microprocessor, which tends to be the CPU of choice in most military and aerospace electronic systems. "Motorola is our CPU choice, and Motorola will have a RapidIO pipe coming directly out of the chip," Malia says.

The F-16 Block 60 engineering and manufacturing development model will be the first aircraft to drop out VME and go to an all-Fibre Channel architecture, Malia says.

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