When eye-diagram measurement speed and accuracy are essential, optimize the 86100 performance with option 500
The eye diagram provides a method to display the overall performance of a transmitter in a single, easy to interpret display. In theory, when an oscilloscope timebase is wide enough to display multiple eye diagrams, once a significant number of samples have been collected, the adjacent eye diagrams are effectively replicas of each other. An exception can occur when the 86100 is triggered with a subrate clock that divides evenly into the data pattern length. Individual eye diagram displays are generated from specific sections of the data pattern rather than the entire pattern (Example: A 128 bit pattern length and a divide by 8 clock results in individual eyes containing only one eighth of the pattern.). The Rapid Eye feature of Option 500 takes advantage of the eye diagram redundancy effect to reduce the time required to create and display the eye while at the same time eliminating the possibility of incomplete eyes when subrate triggering is used.
In Rapid Eye mode samples are collected across an exact multiple integer number of unit intervals (UI). The number can be adjusted by the user. The oscilloscope timebase display span is not required to be an integer number of UIs and is defined by the user by simply setting the timebase display as in normal oscilloscope operation. For example, a common timebase display for an eye diagram is 1.6 UI to show the complete eye as well as the crossing point trajectories leading to and from the eye. In the Rapid Eye display, all samples from the multiple UIs collected will be observed in any complete UI shown. Thus in the 1.6 UI span example, all acquired samples will be displayed between the crossing points of the eye. Since each displayed unit interval contains all acquired samples, adjacent eyes (or portions of eyes) are constructed from the same set of acquired data as the central UI. Wider or narrower timebase displays including any fractional number of UIs, are available, but the underlying acquisition is always of an integer number of UIs .
This process achieves two significant benefits. First, unlike conventional sampling and data display, when an eye mask test is performed, every acquired sample will be compared to the mask, as the central eye is composed of all acquired samples. In the conventional eye diagram, samples displayed adjacent to the central UI are not tested. In the 1.6 UI display example it takes 60% longer to have an equivalent number of samples tested against a mask compared to Rapid Eye. In a 2UI display it takes twice as long as Rapid Eye mode. Second, forcing the acquisition to occur over multiple UI minimizes the subrate trigger effect and generates complete eye diagram displays.