The Design Of Isolated Digital I/O Based On CompactPCI Bus

In order to meet the demand for switch signal processing in the filed of computerautomatic measurement, aerospace monitoring and industrial automatic control, anisolated digital I/O module based on CompactPCI bus is developed, which is mainlyused in the field of control and measurement. The module is not only able to acquire32channels switch signal and drive32channels switching actuator, which is output bysolid state relay(SSR); but also able to achieve timing and counting functions.The scheme of CompactPCI interface chip+FPGA+digital isolation devices hasadopted to achieve the design of isolated digital I/O module. In the CompactPCI businterface design, the PLX corporation’s PCI interface chip PLX9030is used tocommunicate with CompactPCI bus, it is a communication bridge connecting themodule to the host computer. The field programmable logic device (FPGA) is used toaccomplish the task of counting on input switch signal and outputting differentcharacteristics pulse signals. The digital isolation components are used to isolating theinput and output of64-channal signals, and the number of channels can be configuredaccording to the need of users. Therefore, the module has a strong versatility andscalability. Every channel is isolated from others, which can effectively reduce theinteraction affects during testing.In this subject design, the programmable logic device FPGA which is used forprocessing logic tasks is the core of the isolated I/O board. Many parameters of inputsignal can be measured by the module, such as acquiring the state of switch signals,counting buffered events; driving switch actuators, generating the adjustable duty cyclepulse trains and so on. The Verilog hardware language is used to edit the logic code offunctional module and accomplish the design of logic codes. The synthesis andsimulation to all functional modules is accomplished in the integrated developmentenvironment QuartusⅡ8.1platform.Finally, debug the isolated digital I/O board with the driving program and thetesting results show that the isolated digital I/O module can work properly; the requiredfunctions have been accomplished. As a result of the use of the design ideas of universalization, modularization, standardization and miniaturization, the module hasstronger portability and has reference and popularization value to the development ofother similar control devices.