We propose the integration of a network-on-chip-based MPSoC in mixed-criticality systems, i.e. systems running applications with different criticality levels in terms of completing their execution within predefined time limits. An MPSoC contains tiles that can be either CPUs or memories, and we connect them with an instance of a customizable point-to-point interconnect from STMicroelectronics called STNoC. We explore whether the on-chip network capacity is sufficient for meeting the deadlines of external high critical workloads, and at the same time for serving less critical workloads that are generated internally. To evaluate the on-chip network we vary its configuration parameters, such as the link-width, and the Quality-of-Service (QoS), in specific the number (1 or 2) and type (high or low priority) of virtual channels (VCs), and the relative priority of packets from different flows sharing the same VC.

Connection-then-credits (CTC) is a novel end-to-end flow control protocol to handle message-dependent deadlocks in best-effort networks-on-chip (NoC) for embedded multicore systems-on-chip (SoCs). CTC is based on the classic end-to-end credit-based flow control protocol but differs from it because it uses a network interface microarchitecture where a single credit counter and a single input data queue are shared among all possible communications. This architectural simplification reduces the area occupation of the network interfaces and increases their design reuse; for instance, the same network interface can be used to connect a core independently of the number of incoming and outgoing communications. CTC, however, requires a handshake preamble to initialize the credit counter in the sender network interface based on the buffering capacity of the receiver network interface. While this necessarily introduces a latency overhead in the transfer of a message, simulation-based experimental results show that the penalty in performance is limited when large messages need to be transferred, thus, making CTC a valid solution for particular classes of applications such as video stream processing.

We propose Connection then Credits (CTC) as a new end-to-end flow control protocol to handle message-dependent deadlocks in networks-on-chip (NoC) for multicore systems-on-chip. CTC is based on the classic end-to-end credit-based flow control protocol but differs from it because it uses a network interface micro-architecture where a single credit counter and a single input data queue are shared among all possible communications. This architectural simplification reduces the area occupation of the network interfaces and increases their design reuse: for instance, the same network interface can be used to connect a core independently of the number of incoming and outgoing communications. CTC, however, requires a handshake preamble to initialize the credit counter in the sender network interface based on the buffering capacity of the receiver network interface. While this necessarily introduces a latency overhead in the transfer of a message, simulation-based experimental results show that the penalty in performance is limited when large messages need to be transferred, thus making CTC a valid solution for particular classes of applications such as video stream processing.