Inserting test patterns

- Inserting test manually

Choose Manual testpattern input panel. Initially, all input signals are 0. If you want to change the input signal click on the little radiobutton near the name of input. means the input signal is 0 and means that the input signal is 1. The results on made changes can be observed in Circuit window.

When you have chosen the input pattern click Ready button to transfer the chosen pattern to the Testpatterns Table in the right. Now you're ready to insert next testpattern.

Testpatterns can’t be removed from the Testpattens Table one-by-one, clicking the Clear button will remove all inserted patterns from the table.

- Using LFSR to generate test patterns

To generate sets of testpatterns use LFSR configuration panel. Here you can choose between BILBO (Built In Logic Observer) and CSTP (Circular Self Test Path) mode. The length of the register (in bits – every bit means a trigger of a register) can be defined in a field below the mode choice. When doing that you should remember that the output of the register controls the inputs of a design under test. Therefore, the length of the register should be at least the same as a number of inputs of the design. When working in CSTP mode you should also remember that the length of a register should be bigger that a number of outputs of a design.

After defining general parameters of LFSR, it is time to configure the initial state and feedback of the generator using two columns on LFSR panel – the left one to define the initial state and the right one to define feedback. There are no certain rules for doing it. Test pattern giving maximum fault coverage or the coverage of important faults can be used as an initial state of the generator. For defining the feedback, primitive polynoms are usually used. Initial state of the register and feedbacks can be defined using radiobuttons. means there is a feedback, means there is no feedback.

The number of testpatterns to be generated can be defined in a field below the LFSR initial state and feedbacks panel. The current value of the field is 1. The maximum value is 256.

To generate whole set of testpatterns of desired size, click the Start button. To generate testpatterns one-by-one click the Step button. This way you can observe the work of LFSR more closely. After transferring the defined number of test patterns to the table the new initial state of pattern generator is the state of generating the last pattern of a set.

Testpatterns can’t be removed from Testparrens table one-by-one, clicking the Clear button will remove all inserted patterns from the table.