The Design Of VXIbus-based Multifunctional Counter Module

Four-channel counter module based on VXI bus, developed successfully by Research Institute of Automatic Test and Control of Harbin Institute of Technology, has been applied widely in many models of automatic testing systems based on VXI bus, because of its high measurement precision and complete measurement function. However, this module exposes some questions gradually along with the developed electronics and increasement of practical requirement. The main questions are that the measurement precision and measurement range of frequency could not meet higher and higher practical requirement, some electronic components adopted have stopped production or could not keep up with the era development, poor integration of digital circuits and the comparative level value could not be set with the actual requirement. So it is necessary to redesign this counter module, to meet the practual requirement and contribute for our national defense.This thesis analyzes the disadvantages of the original module, redesigns on the original four-channel counter module based on VXI bus by adopting some new techniques and new electronic components. Advanced FPGA technology is introduced to improve the integration of digital circuits, and all digital circuits in the original module are integrated in the FPGA chips, which could not only reduce the cost, but also improve the reliability and measurement precision of the circuits. High speed Digital Signal Processor (DSP) is selected as the coprocessor instead of SCM; it can receive all kinds of commands sent from VXI, analyze and execute the commands, harmonize each section of the module and process the data. Higher-conversion-speed comparator chip is adopted to convert the input signals being measured into square waveform signals which could be identified by FPGA chip; it can expand the measurement range of frequency dramatically. D/A conversion chip and isolation amplifiers are used to obtain the comparative levels required by isolation channels, which could be set with actual requirement; it can enhance flexibility of the module. Otherwise, four-channel isolation signal sources are exported using D/A conversion chip and isolation amplifiers as well. The output isolation signal sources could be switched to...