Agilent 5991-3956EN Generating Looped Test Patterns or PRBS Signals with a Preamble - Application Note c2014 free download

File name 5991-3956EN Generating Looped Test Patterns or PRBS Signals with a Preamble - Application Note c2014

Keysight Technologies Generating Looped Test Patterns or PRBS Signals with a Preamble Application Note Some digital integrated circuits (IC) use special modes to test all the internal states of opera- Problem statement tion. To get into such a mode the IC requires a defined command be sent to the device under test (DUT). As shown in Figure 1, in some instances a portion of the test pattern is used once to advance the special IC mode to an area of operation that requires repetitive use of a test pattern in order to thoroughly test the device. Play once Play multiple times Preamble Test pattern Figure 1: Flow chart of the test signal generation It is very important that the test pattern and the preamble are correctly timed and generating such a sequence may not be a trivial task. If the test pattern is not received at the necessary time, the device can time out and return into a pre-defined state, delaying testing, because the preamble must be rerun to bring the DUT back into the desired test mode. Both the Keysight Technologies, Inc. 81150A and 81160A pulse function arbitrary generators Solution proposal have the capability to generate such test signals. They offer two ways to create these signals. One way is through the use of the built-in pattern sequencer; the other is using the channel add capability. To illustrate these functions, this application note provides examples using the 81160A model shown in Figure 2, though they also apply to the 81150A. Additionally, this paper highlights the advantages and disadvantages of each of the options. Figure 2: The Keysight Technologies 81160A pulse function arbitrary generator. 2 Using the pattern sequencer is a very simple and straight forward way to generate test signals. Pattern sequencer In the Pattern Editor menu of the 81160A (shown in Figure 3) the user defines the preamble and solution approach the required test data pattern, then uses a pointer to define the beginning of the loop sequence. The number of loops is defined in the Burst menu and typically the user defines when the test signal should start playing. Once the output is activated, the test signal can be captured and visualized with the help of an oscilloscope. Figure 3: Pattern Editor menu of the 81150A and 81160A. 3 A pattern sequ