LeCroy SDA, Operator'S Manual

Page: 318 / 397

Eye Setup
The PLL must be set up or an appropriate external clock must be supplied in order for the mask
test function to operate.
1. Touch
the Mask Test button. The "Eye Diagram" dialog opens.
2. Touch inside the Mode field and select either Sequential
6
or Traditional
7
from the pop-up
menu:
3. Touch inside the Persistence field and select persistence mode: Monochrome or Color
graded . The Monochrome selection will display frequency of occurrence in levels of intensity
of the same color, while the Color graded selection will use a color spectrum to indicate
frequency of occurrence.
4. If you would like to display another time-synchronized signal in its own grid, touch inside the
User Signal field and select another signal source from the pop-up menu. This will enable
you to see the signal correlated to the failed bits in the eye mask when using the eye mask
failure locator.
5. The Mask Type
8
field allows you to select different modes for the selected standard.
Individual modes for a given standard define specific masks; for example, transmit or receive.
6. Under "Measure" touch inside the Type field, then select a set of parameter measurements
from the pop-up menu:
.
6
The Sequential eye pattern is created using a long acquisition of waveform data that is then processed to generate a
recovered bit clock, and divided up into bit-sized segments that are then overlaid in a persistence map. The clock signal
control is not used in this mode.
7
The Traditional eye pattern is created by capturing, in a persistence display, many short records on the order of one bit
interval (equal to the inverse of the bit rate). The SDA is triggered by an external trigger signal, which is designated in the
Clock field.
318
SDA-OM-E Rev H
8
Each standard has a set of required tests. Some of the standards specify several types of masks. So a single standard
can have a normalized mask and/or absolute mask for the transmitter. The standard requires you to make sure that the
signal passes both the normalized and the absolute masks.