As the Airbus 380 program moves forward, a specialist avionics data bus supplier enjoys a lead in producing test cards for the super jumbo’s real-time version of the 10/100-megabit/sec (Mbit/sec) switched Ethernet network.
Boeing already uses 10-Mbit/sec full-duplex, switched Ethernet for the display system on its 767-400ER. But the A380 will deploy a 10/100-Mbit/sec Ethernet data communications system. The airplane’s avionics full-duplex switched (AFDX) Ethernet connects onboard systems, such as the displays, flight management systems (FMS) and electronic engine controllers. (Some of the essential aircraft functions also will use the ARINC 429 data bus as a backup.)
AFDX employs communications techniques derived from the commercial Ethernet standard, IEEE 802.3, along with such aviation-specific embellishments as "virtual links" and "traffic shaping" between end systems, the interfaces between line replaceable units (LRUs) and the network. These refinements guarantee that critical information is delivered on time and that sufficient bandwidth is allocated to necessary data flows.
An EU Effort
AIM GmbH, a German test hardware and software company known for its work in Mil-Std-1553 and ARINC 429, has benefited from ground-floor participation in the A380 project. Two years ago, AIM took part in a European Union (EU) -funded project that first looked at the use of high-speed Ethernet on Airbus aircraft, says Doug Ullah, director of sales and marketing in AIM’s London office. A successor program will continue this work.
As a result of the EU technology effort, AIM designed the first AFDX test and monitoring card, the ACI-FDX-4, in the 6U form factor. Built in the Compact PCI format, the card is available in four-port and two-port (ACI-FDX-2) versions. Each port implements a 100-Mbit/sec, full-duplex Ethernet interface. (The cards also support 10-Mbit/sec functions.)
The ACI-FDX-4 base board, like AIM’s other AFDX cards, features:
16 megabytes (Mbytes) of global random access memory (RAM),
64 Mbytes of application support processor (ASP) RAM,
Dual ARM, 200-MIP, RISC bus interface unit (BIU) processors, and
A single 150-MIP, RISC ASP.
(MIPS refer to millions of instructions per second; RISC, to reduced instruction set computer; and PCI, to peripheral component interconnect.)
AIM also has created AFDX cards in PCI, PCI mezzanine card (PMC) and VME formats. The company plans a companion board in the VXI format.
The reason the company has been able to field cards quickly is that they are based on a common core hardware architecture. The boards share features across formats: global RAM, BIU RISC processors, and dual ARM RISC devices. The underlying base board is exactly the same, Ullah says. Plug-in, "piggy back" boards with field programmable gate arrays (FPGAs), physical interface chips and specific magnetics are added to adapt to different bus or network standards.
AIM’s AFDX cards can receive and generate traffic, analyze virtual links, perform error detection/injection, decode/encode data, monitor traffic, and verify that AFDX messages are transmitted with guaranteed, "deterministic delivery," in accordance with Airbus protocols. The board also can be used to test AFDX switches and to monitor communications between end systems, between end systems and switches, and between the switches themselves. Each A380 contains 18 switches–in two, redundant nine-switch networks–provided under a sole source contract by Rockwell Collins.
Avionics developers are using the tool, Ullah says. For example, Honeywell, which supplies the A380 FMS, could use the AIM card to emulate systems in order to monitor data, and test and verify avionics system performance on the network. A single card, in a portable PC, could function as a simple bench tester in an avionics shop. Multiple cards could power a rig tester for an integrated avionics system.
Timing verification is important in avionics functions, where data has to reach its destination within strictly defined limits. AIM’s AFDX boards have IRIG-B time code processors that generate time stamps. "You can time tag when information was received and whether there was a delay going through the network," Ullah says. You can measure how long it takes a packet of information to go from an end system, through a switch and to another end system.
AIM also offers optional AFDX network analysis software that runs on the network cards. The fdXplorer package is generic in its way of setting up traffic generation and monitoring but allows some customization of screen presentations. Users can set up virtual links and monitor selected traffic in a Windows environment.
At the moment AIM has little competition in the AFDX test card market, Ullah contends. "There are people with standard Ethernet cards, but ours have been adapted to handle the AFDX protocol." More than 20 cards have been sold.
Looking into the future, AIM expects to enhance its common core hardware. The company plans to upgrade its PMC cards, for example, to accommodate higher-speed BIU processors and newer memory technology, as parts become available. The application programming interface (API) would stay the same regardless of hardware modification, so the commands to control the card won’t change, Ullah says.