The Design And Implementation Of The PCB Schematic Recovery Software

In the courses of fault diagnosis and servicing of electronic devices,circuit schematics were the basis of fast fault ponts location and maintenance. Among lots of electric devices,about 25% didn't have their schematics.Therefore,these schematics had to be recoveried form their printed circuit boards(PCB).In order to improve the capability in fault diagnosis and maintanence,shorten the maintaining cycle,a set of schematic recovery system have to be developed.In this system,unkonown PCB are measured and recoveried in the control of computer.And then,the schematics are brought into the automatic test and diagnosis patform.The whole process of schematic recovery system is made up of measureing and logic synthesis.This article discussed the logic synthesis which is the important components in schematic recovery system.They are logic reverse software circuit recognition software and netlist compare software. The implementation make use of measured netlist and transform it into circuit schematic.This schematic is compatible with protel.The article analysed and summarized the storage format of schematic librarie and symbol libraries in Protel and design data structure and arithmetic according to their storage format.It also introduced the design and implementation of logic reverse software and netlist compare software. The article design object based programming method to implement the functions in this software. Through local library building module,logic symbol layout module,net loading module and schematic logic settlement module, we input the measured netlist and pick up the informations of the components, the logic synthesis transforms the netlists built by netlist building software into schematics compatible with Protel.Circuit recognition software could recognize functional circuits according to typical circuit units or user-defined circuits.Design and implement the netlist compare software. It compares the distinctness between netlists created by logic reverse software and netlist building software. The netlist compare software is very useful to compare and check the whole recovery process. The netlist compare software contains four function modules:file location module,net connetion pick up module,net connection module and result output module.The netlist compare arithmetic has two ways to implement:conten based method and desination based method.