Design Of PLC Source Program Compilation And Internal Communication System Based On ARM And FPGA

The structure ARM-FPGA is used for PLC host in the paper. The running processcontrol of the PLC host and the part execution of the PLC instruction are achieved inARM processor. The function for logic, arithmetic and the timer/counter of the PLC hostare achieved in FPGA system. The hardware of ARM system is LPC2478developmentplatform based on ARM7kernel. And the software system mainly includes real-timeoperating system μC/OS-II, PLC instructions compiler and CAN communication programbetween the PLC host and the external equipments. Preliminary researches for the PLCinstruction compilation system and the CAN communication system based on ARMprocessor have been done by the research group.The research of this object is mainly to conduct further design and optimization andimprovement based on the original compilation system of PLC instruction and the CANcommunication system. The research results mainly include:1) The working process of PLC system and the characteristics of the PLC instructionare analyzed. The PLC user program compilation method is elaborated according to thecharacteristics of the PLC instruction and the operation mode of the FPGA system,including static compilation and dynamic compilation processes. Instruction operands areconverted to the direct address of PLC soft components and transfer address list is set upfor transfer class instruction in the static compilation process. The new PLC user programcode is generated after the static compilation process. The direct addresses of instructionoperands in the new PLC program are converted to the immediate in the dynamiccompilation process for the PLC execution. The instructions are carried out by the FPGAsystem after the dynamic compilation process.2) The optimization schemes are given according to the original compilation system,including increasing the number of instructions that PLC system can handle and usinglook-up table method instead of the displacement method as the initialization method forsoft component image area.3) The setting method to the communication protocol and the point-to-pointcommunication mode of the CAN communication system are expounded. And thecommunication requirements and the communication characteristics in the state ofelectricity initialization, edit and run are analyzed. Protocol and the identifier areoptimized according to the original design of the CAN bus communication. CAN receivetask is designed to interrupt function. These optimizations improved the flexibility of thecommunization process. 4) Functional tests and performance comparison tests of the PLC instructioncompilation system and the CAN bus communication system are conducted throughspecific examples. Test results show that the data information can be effectivelytransmited on the CAN bus using the CAN communication system and the instructionscan be accurately compiled using PLC instruction compilation system.