Starting with a known good signal, a vertical and horizontal tolerance limit is specified, and the scope's software algorithm automatically generates a test envelope about the signal on the display. Tolerances can be changed to provide custom test specifications. It is also possible to start with a standard mask and modify it for specific testing. Some scopes' telecom masks are simple text files, and can easily be modified on a PC using a word or data processing application. The new modified mask can then be reloaded into a scope for customer mask testing.
Signal integrity is the ability of a signal to respond in a circuit at the proper time and voltage.
Signal integrity problems can arise from incorrect placement of ICs in a design, termination components, or improper routing of high-speed signals. The design can then produce bad data output, function intermittently, or not function at all, displaying false triggering, ringing, overshoot, or undershoot, or exhibit setup and hold time problems. A design has good signal integrity if its signals arrive at the required time, duration, and voltage. Likewise, manufacturing engineers will find that the ability to test several parameters with a single test can speed throughput on a manufacturing line. Instead of making four or five individual measurements such as Vmax, Vmin, period, risetime, and falltime, a single user-defined mask with acceptable tolerances can test for all of these parameters in a single test.