The Research Of Programmable Logic Device Simulation Based On ABEL Language

Along with the development of information technology, as an effective complement of traditional experiment for teaching, virtual experiment has become the important means of enhancing practice and improving the quality of teaching. The construction of virtual laboratory usually based on virtual apparatus model at present. But there is a problem about construction of function model when using this method to simulate the device with uncertain logic function. The method based on circuit simulation technology can solve this problem effectively.After in-depth analysis of the forms of organization and structure of virtual laboratory and the development process of Programmable Logic Device (PLD) in traditional environment, a simulation strategy of PLD is put forward considering the feature of PLD experiment. This way of simulation modeling the circuit designed by user first, and then simulates the parallel operation of circuit, so as to archive the aim of simulation of PLD. Construction of the model of circuit has two aspects: firstly, analyze architecture of the circuit which is described by Advanced Boolean Expression Language (ABEL), then design format of the file which is used to save the model information of circuit; secondly, extract circuit model information from ABEL source file through the implementation of semantic analysis about ABEL. Simulate the operation of circuit means archive the effect of parallel operation of actual circuit under the control of scheduling algorithm. To archive this goal, the event-driven simulation algorithm is adopted and modified to suit for the simulation system, and it is implemented in the scheduling module of simulation system. Beyond that, the data structure which is used in scheduling module and interface that communicate with external system are designed, also the simulation of kinds of syntax of ABEL and waveform display about the simulate result are accomplished.The PLD simulation system is implemented and tested with two typical and practical examples. The result indicates that the system meets the expected design demand. The research achievement not only solves the simulation of device with uncertain logic function effectively, but also provides a new perspective for the research of virtual teaching laboratory.