ANSI EIA 364-107:2000 pdf free download – Eye Pattern and Jitter Test Procedure for Electrical Connectors, Sockets, Cable Assemblies or Interconnection Systems
4.3.1.4.1 If the automatic measurement function is not available, position two vertical cursors, one on each side of the eye cross transition; see figure B.6.
4.3.1.4.2 Read the jitter value from the delta (distance between) the cursor positions.
4.3.2 Method D, pulse test, (single pattern)
4.3.2.1 Set the generator for a DC balanced test pattern. This shall be a square wave or PRBS pattern at the specified frequency.
4.3.2.2 Set the oscilloscope to infinite persistence display mode, and adjust the vertical position to center the waveform vertically on the display, with half amplitude at center screen.
4.3.2.3 Adjust the generator to produce the specified test pattern. This pattern may be chosen to simulate a long idle sequence, and is specific to the data pattern to be used in the application. It is typically a pattern of a logic “1” followed by twenty or more logic “0”s. For single ended measurements: measure the logic “1” and logic “0” levels, and adjust the generator if necessary to ensure the half amplitude of the waveform is still at center screen. For differential measurements: measure the logic “1” and logic “0” levels of both channels. Adjust the generator to minimize the offset in voltage or time between channels. If any voltage offset is present between channels, the amount of offset shall be added to or subtracted from (as appropriate) the half-amplitude measurement point for the pulse width in 4.3.2.4.
4.3.2.4 Measure the width of the pulse that crosses the half-amplitude point (center screen), using cursors or oscilloscope measurement functions; see figure B.7.
4.3.2.5 Subtract the half-amplitude pulse width measured in 4.3.2.4 from the bit time (1 divided by the clock frequency of the generator) to obtain the jitter.
B.1.6 A PRBS is a data stream, i.e. a sequence of bits, that has a very long period. Within the period it looks like a random string of 1’s and 0’s. The longer the period of the PRBS, the more random it looks. The PRBS has virtually all the statistical characteristics of a truly random signal. It appears as such to the device under test. A range of maximal length PRBS patterns has been specified by the CCITT (International Telephone and Telegraph Consultative Committee) for bit error rate testing and are frequently used for eye pattern testing as well. Typically the higher the data rate, the longer the bit sequences range in length from 215 –1 bits at a data rate of 1.5 Mbits/sec to 223-1 bits at 139 Mbits/sec. A sequence length of 215 –1 bits is sometimes used for testing at Gbit/sec data rates. B.1.7 Signal attenuation and dispersion as well as noise caused by EMI, crosstalk, and reflection noise due to impedance mismatches all cause waveform distortions that tend to reduce an eye pattern opening. Interconnection systems affect eye pattern responses because they exhibit rise time degradation, pulse spreading, ringing, overshoot, undershoot, and crosstalk, have impedance discontinuities, and are susceptible to EMI. These various characteristics tend to distort the eye pattern response and reduce the eye opening. B.1.8 An eye pattern is evaluated quantitatively by comparison to a mask or by measuring the eye opening. A mask defines a forbidden area within the eye. All signal energy should fall outside the mask; no energy should fall within the mask. An eye pattern having sufficient opening so that no part of the signal falls within the mask area typically indicates reliable, error- free transmission; see figure B.3.