Generate Looped Test Patterns or PRBS Signals with a Preamble
Application Notes
Problem statement
Some digital integrated circuits (IC) use special modes to test all the internal states of operation. 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.
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.