Abstract
The static resource allocation in time-triggered systems offers significant benefits for the safety arguments of dependable systems. However, adaptation is a key factor for energy efficiency and fault recovery in Cyber-Physical System (CPS). This paper introduces the Adaptive Time-Triggered Multi-Core Architecture (ATMA), which supports adaptation using multi-schedule graphs while preserving the key properties of time-triggered systems including implicit synchronization, temporal predictability and avoidance of resource conflicts. ATMA is an overall architecture for safety-critical CPS based on a network-on-a-chip with building blocks for context agreement and adaptation. Context information is established in a globally consistent manner, providing the foundation for the temporally aligned switching of schedules in the network interfaces. A meta-scheduling algorithm computes schedule graphs and avoids state explosion with reconvergence horizons for events. For each tile, the relevant part of the schedule graph is efficiently stored using difference encodings and interpreted by the adaptation logic. The architecture was evaluated using an FPGA-based implementation and example scenarios employing adaptation for improved energy efficiency. The evaluation demonstrated the benefits of adaptation while showing the overhead and the trade-off between the degree of adaptation and the memory consumption for multi-schedule graphs.
Highlights
Safety-critical Cyber-Physical System (CPS) demand assures services under all considered load and fault assumptions in order to minimize the risk for people, property and the environment
This paper introduces the Adaptive Time-triggered Multi-core Architecture (ATMA) that fulfills these requirements
This paper introduces the overall architecture of an adaptive time-triggered multi-core architecture along with the interplay of agreement, adaptation and meta scheduling
Summary
Safety-critical CPS demand assures services under all considered load and fault assumptions in order to minimize the risk for people, property and the environment. A priori knowledge about the permitted temporal behavior can be used by network guardians or operating systems for isolating faulty messages or tasks, thereby preventing fault propagation via shared resources This fault containment is a prerequisite for active redundancy as well as modular and incremental certification [2,3]. This paper introduces the Adaptive Time-triggered Multi-core Architecture (ATMA) that fulfills these requirements. The combination of agreement, adaptation and meta-scheduling as part of a time-triggered multi-core architecture supporting implicit synchronization, fault containment and timeliness is an open research problem. The paper builds on previous work of the authors where a non-adaptive time-triggered multi-core architecture [6] was introduced as well as individual components for agreement [11]. The paper introduces adaptation concepts for time-triggered systems and describes the services and system properties, which are essential to preserve implicit synchronization, temporal predictability and avoidance of resource conflicts.
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