The Research On Real-time Operating System For System-on-chip

With the quick development of deep sub micron semiconductor technology, more and more systems on chip (SOC) have been developed for real-time systems. With the methodology of hardware/software co-design, there must be the software parts as well as the hardware parts on SOC. There is a growing consensus that the real time operating system (RTOS) has become an indispensable part of SOC. The RTOS can not only improve the performance and reliability of the system, but also simplify the development and debugging of SOC. In this dissertation, the design and implementation of a SOC-based real-time operating system, named Iota, has been presented.Compared with the general embedded RTOS, the SOC-based RTOS has its own specialities. The SOC environment acquired new features for RTOS. For example, the hardware/software co-design brings new methodology for the SOC-based RTOS. Some functions of the RTOS can be implemented in hardware. Furthermore, the memory size of the SOC is small even compared to the embedded systems. The foot-print of the SOC-based RTOS should be smaller than the embedded systems.In this dissertation, the RTOS is designed with the hardware/software co-design methodology. The scheduling policy of the bus arbitration unit was been analyzed and the I/O function of RTOS was partly implemented in hardware. By this way the performance and the throughput of the SOC are increased.The RTOS should focus on the real-time properties of system. In this dissertation the TS demultiplex task and AC-3 decoding task in MPEG-2 protocol are scheduled by 2 policies. One is the buffer-drive policy and the other is deadline-drive policy. Some experiments have been done to confirm the policy and the arguments of the scheduling.The memory management is important in the OS. According to the features of the MMU of the RISC Core, a simple memory protection and share mechanism was designed in Iota. The RTOS is in kernel mode while the application is in the user mode, the direct access from the user mode to kernel mode is denied and the access from one application program to another application is prohibited too. The memory protection and share mechanism can improve the reliability of the system.A new methodology for the hardware/software cosimulation using RTOS was introduced in this dissertation. The complexity of SOC required the different simulation platform. The RTOS is useful to build a hierarchical structure of the application, thus the application can be tested on different simulation platform with little modification. The RTOS can accelerate the simulation progress in SOC development.