Agilent English 2012-10-01 PDF 344 KB 5991-1128EN c20121025 [4] free download

File name English _ 2012-10-01 _ PDF 344 KB 5991-1128EN c20121025 [4].pdf

Agilent 33500 Series Waveform Generators PRBS Pattern Generation Technical Overview Testing digital devices typically requires sending a series of alternating high and low voltage values (bits) to the device under test (DUT). If these bits are easily predict- able, the test coverage will be limited to a small set of possible scenarios. For this reason, it is often helpful to send a near-random stream of bits, such as the one shown in Figure 1, to the DUT. To generate this type of bit stream, the Agilent 33500 Series waveform generators include a pseudo-random binary sequence (PRBS) waveform generator. A PRBS waveform is generated by a linear feedback shift register (LFSR) like the one shown in Figure 2. Figure 1. A near-random stream of bits The branches after register cells 5 and 9 are called taps, and the configuration of the LFSR and its taps determines the PRBS waveform. Figure 2. A linear feedback shift register How to generate a PRBS waveform from the front panel From the front panel, press [Waveforms] > More > PRBS > [Parameters]. You can then specify the polynomial function used to generate the sequence (7, 9, 11, 15, 20 or 23 register cells), the bit rate at which the sequence plays (up to 50 Mbps), and an edge transition time that is used for both rising and falling edges. Figure 3. PRBS menu FUNCtion:PRBS:DATA The number after the PN How to generate a PRBS waveform using SCPI {PN7|PN9|PN11|PN15|PN20|PN23} specifies the LSFR length. An LFSR of length L results You also can generate PRBS waveforms using the Standard in a bit sequence of length Commands for Programmable Instruments (SCPI) program- 2L-1. ming language. The equivalent SCPI commands are: FUNCtion:PRBS:BRATe The can range from 1 Mbit/s to 50 Mbit/ sec FUNCtion:PRBS:TRANsition[:BOTH] The edge transition time for leading and falling edges, fr