Mục tiêu là phát triển một hoặc nhiều đường dẫn xác định một quá trình chuyển đổi từ trạng thái hiện tại của các mạch hoặc từ một trạng thái thiết lập lại, và bằng phương tiện của mạng Petri, xác định một chuỗi các đầu vào mà các ổ đĩa mạch cho Mục tiêu. | THE TEST DESIGN EXPERT 607 The objective is to develop one or more paths that define a transition either from the current state of the circuit or from a reset state and by means of the Petri net identify a sequence of inputs that will drive the circuit to the Goal. In either case the traversal is directed by means of input stimuli. By virtue of having several paths from leaf nodes to the Goal several options exist. One option is to traverse the shortest path from the leaf node to the Goal. Another option is to traverse a path that includes branches that have not yet been traversed in order to exercise heretofore unexercised logic. It may be desirable to spread out the traversals choosing different paths each time so that a manufacturing test program exercises all paths approximately the same number of times rather than exercise the same path repeatedly. However recognizing that tester time can be quite expensive the goal of a manufacturing test program usually is to be as short and efficient as possible so it may be desirable to find the least cost path. From Figure it can be seen that the searches can grow out of control quickly and the example circuit was rather small. The SCIRTSS project spent much effort developing cost functions to help navigate through the logic and prune the search trees in order to find shortest paths as well as to control the growth of goal trees. THE TEST DESIGN EXPERT The Test Design Expert TDX was a commercial endeavor motivated by the SCIR-TSS system and it bore some resemblence to it. But TDX included strategies techniques and refinements that took it beyond SCIRTSS and some of the features that it had in common with SCIRTSS were evolved and refined. Inputs to TDX included a netlist and an RTL description. It also employed a map file to link storage elements in the RTL with their instantiated counterparts in the netlist. An Overview of TDX Like SCIRTSS TDX used search heuristics to explore RTL models but as it .
