Features

Advanced Integrated Architectures

Different variants of generic open architectures can be implemented by using VPX-based Ethernet backplane and backbone networks, assuming they provide absolute temporal guarantees and determinism for different critical functions (Figure 3).

Control-plane applications in VPX typically use single- or dual-star (redundant) topology with switched Gigabit Ethernet, which are also supported by VPX switches with SAE AS6802 QoS (TTEthernet switch). Depending on the application, TTEthernet switches can be used for control plane, data plane, and some utility plane applications (synchronization) in VPX-based systems. This means all functions and modules connected to backplane and backbone networks operate as if they are connected directly to a large, fault-tolerant Ethernet backbone. By allowing robust TDMA partitioning of networking resources, the system designer can determine the level of integration/interaction or isolation among different functions. This enables the design of innovative architectures and distributed platforms that can host many distributed functions using shared computing/ networking resources for advanced integrated system architectures.

In deterministic Gigabit-Ethernet networks, it is possible to emulate reflective memory by using a periodic global data exchange with applications that are synchronized to the global timebase generated at the network level by SAE AS6802 services. From the logical perspective, different distributed functions gain a private, congestion-free shared memory. By using this approach, we can scale the level of functional integration without influencing other existing functions in the system. Also, distributed applications do not need to know about underlying architecture or topology.

Therefore, sensor fusion and distributed payload processing can be executed without fear of unintended interactions with other system functions. Voting on data from synchronous sources simplifies redundancy management and application software design. Obsolescence management, modernization, and upgrades with new DSP processors and applications are simplified, as the behavior of already integrated functions will not change and cause new system integration or timing issues. Critical, hard real-time functions will not be influenced by other less critical distributed functions. Sensor front-end data can be streamed to platform systems or common core computing systems, with exact latency and no jitter, independent of network load. This also means that processing functions do not require spatial proximity to a specific sensor, and can be placed anywhere in the system. This also simplifies reconfiguration, upgrades, and incremental modernization.

Summary

VPX modules and VPX-based Ethernet switches like those shown in Figure 4, which implement SAE AS6802 and ARINC664 and support Gigabit (or higher) bandwidth, support the design of open generic architectures in which the operation and interaction of all critical functions can be defined at design time, and new functions can be integrated with minimal impact on existing ones. This significantly reduces costs and effort in all phases of system lifecycle, and allows integration of robust hard RT functions in integrated embedded systems hosting safety-, time-, and mission-critical functions. Here-with, the design of integrated modular architectures, which follow key objectives of MOSA (Modular Open System Acquisition) and IMA DO-297 (Integrated Modular Architectures – Design Guidance and Certification Consideration), can be applied in complex Ethernet and VPX-based embedded systems.

This article was written by Mirko Jakovljevic, Senior Marketing Manager, and Perry Rucker, Director of Sales, TTTech North America Inc. (Andover, MA). For more information, Click Here.

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