A RTSJ-based Java Processor And API Implementation For Embedded Real-Time System

The complexity of embedded real-time systems keeps growing and novel methods and tools are required. Compared to software development for desktop systems, current software design practice for embedded systems is still archaic. C/C++ and even assembler are used on top of a small real-time operating system. Many of the advantages of Java, such as safe object references, the notion of concurrency as a first-class language construct, and its portability, have the potential to make embedded systems much safer and simpler to program. With the advantages mentioned above, Java is increasingly expected to become the leading programming language in embedded systems.Most of the embedded systems are real-time systems. Java technology is seldom used in embedded systems currently, due to the lack of acceptable real-time performance. To improve the real-time performance specified in the Java Language Specification and the Java Virtual Machine Specification, Greg Bollella et al propose the Real-Time Specification for Java (RTSJ). It provides a guideline for the implementation of real-time Java platform.Currently, to provide an efficient Java platform suitable for real-time applications, many different implementations are proposed. These implementations can be generally classified as Interpreter (an interpreting program running on the operating system that can interpret and execute java bytecode under the assistance of the OS), Ahead-of-Time Compiler (Java bytecode is compiled into native code or an intermediate language such as C in advance), and Java Processor (the Java platform is implemented directly on silicon) etc. Java processor not only avoids the overhead of translation of the bytecode to another processor's native language, but also provides special support for Java runtime features such as stack processing, multithreading etc.Comparing with other implementing techniques, Java Processor is preferable in embedded systems for its high execution efficiency, low memory footprint and power consumption. Therefore, it becomes popular in implementing embedded real-time Java platforms. Presently, aJ-80/100 provides solution for employing Java technology into smart mobile devices and consumer appliances etc. The flexibility makes it a little too complex to implement. FemtoJava and JOP are simple to be implemented but do not put emphasis on supporting the RTSJ.In this paper, Based on the NSF(National Science Foundation) project—Highly credible computation platform(SoPC) research for real-time system(code: 60703106). We have designed the PRTEJ (Pipelined Real-Time Embedded Java Processor) implemented in FPGA. Its purpose is to implement the embedded Java processor with real-time character, and to support the RTSJ(Real-Time Specification for Java). Our Java processor is a six-pipelined embedded Java processor running in FPGA. We also define the special pipeline, Instruction Set and Memory Management mechanism for the Java processor. Furthermore, We can provide our Java processor to support the RTSJ from the low-level hardware to the upper-leverl software, such as memory management, CConvertor, and API system, after We have learned and researched the RTSJ.