Configurable Hardware/Software Support for Single Processor Real-Time Kernels

Today's software based real-time operating systems (RTOS) have the ability to be configured in order to decrease memory footprint, important when the RTOS is used in resource restricted embedded environments. When the kernel is implemented in hardware, not only memory footprint is motivation for configuration for minimization, the number of logic cells occupied in the PPGA has to be considered as well. We have modified existing hardware support, the real-time unit (RTU) for increased configurability. The modified RTU was compared regarding configuration and footprint with a corresponding system based on the commercial software RTOS MicroC/OS-ll. Four different configuration settings were compared and the results show that the RTU memory footprint was 24% to 38% of the size of the MicroC/OS-II footprint. In FPGA area, the smallest configuration of the RTU occupied only 50% of the logic cells used by the largest configuration. Configurability of an RTOS with hardware support, like the RTU, decreases project cost since it is more likely to be able to use a low cost FPGA when adjusting implemented functionality to only include what is required by the application.