Reconfiguration Management in the Context of RTOS-Based HW/SW Embedded Systems

HW/SW interface for an embedded system-on-chip is an important topic. It allows communications between tasks independently of their implementations. In our adaptive strategy, communications are not limited to data since local data (task context: recursive data, counters), configuration (pointers, configuration ID), and metrics are also exchanged. Thus, task communications are encapsulated within a unified interface called UCCI (see Figure 1) that handles configuration, data, and control communications in such a way that usual SW and HW implementations can be directly instantiated in the new framework. Each HW task has a legal representative (LR) which is a lightweight SW task that maintains communications between RTOS and tasks implemented in hardware. Local data can be read (resp., written) by the LR in case of HW to SW (resp., SW to HW) migration or by the HW UCCI in case of HW to HW migration. Basically, a context transfer is equivalent to a data transfer performed between reconfigurations in case of HW to SW or HW to HW migrations. The UCCI implementation imposes some constraints regarding I/O format. For instance, local data are based on identical stacks for all HW and SW versions. Moreover, some SW routines have been added for data format adaptation; the more used one is the bit/byte conversion routine required when SW tasks accede to binary images where pixel is coded as bit for bandwidth and area optimization. 2.2.2. Tasks communication Communications with an SW task are involved to call the intertask communication RTOS services. Two kinds of operation can be used: post and pend communications. For SW → SW communications, traditional communication services are used, whereas in HW ↔ SW communications, the LR task Y. Eustache and J.-P. Diguet 3 Architecture configuration Dataflow configuration