Embedded Real-time Java Processor Research

Many of the benefits 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 for programming. With the advantages mentioned above, Java is increasingly expected to become the leading programming language in embedded systems. 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, Ahead-of-Time Compiler, and Java Processor 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.This paper presents a Java processor, which is implemented as a soft core for time-predictable execution of real-time tasks. JPOR (Hard Real time Embedded Java Processor) is the implementation of the Java virtual machine in hardware, based on HRTEJ (Hard Real time Embedded Java Processor). It increases addressing space and strengthens the overall performance, the improvement as follows:Firstly, compared to HRTEJ, JPOR uses the structure of three buses BUS A, BUS B and BUS C. The width of register group is 32-bits, strengthen the ability of the data processing. Enables the virtual machine to be possible to apply in the request higher real-time environment.Secondly, design of pipeline. The stack architecture introduces 3 stages pipelines for Java bytecode, including fetch bytecode, fetch the instruction and decode, execute and write back. The microcode instruction system has used 36-bits forms, enhance the data processing speed, causes data path's control mode simpler.Third, design of clock. The clock network uses the global clock network in FPGA (field programmable gate array), replaces the original counter, which strengthens the drive.Finally, the paper proposes architecture of JPOR, use hardware language VHDL (Very High Speed Integrated Circuit Hardware Description Language) describe all the models, and gets the simulation. It is tested in the platform of Xilinx Spartan 3 and got the partial simulation, which indicates this Java processor could work in the low cost FPGA. This research demonstrates that a hardware implementation of the Java virtual machine results in a small design for resource-constrained devices, and Java Processor is preferable in embedded systems for its high execution efficiency, low power consumption. Therefore, it becomes popular in implementing embedded real-time Java platforms.