SDA Operator’s Manual
Transition/Non-Transition Eye Diagram
A dual display eye diagram is formed with bits that are of non-changing polarity (non-transition)
and changing polarity (transition). This display mode is useful for those serial data standards that
utilize mask testing for both types of bit sequences (PCI Express and FB-DIMM Point to Point).
Transition Mode
For example, Section 4.3.3.1 of PCI Express Specification defines the requirements for Transition
and Non-transition eye diagrams:
“There are two eye diagrams that must be met for the Transmitter. Both eye diagrams must
be aligned in time using the jitter median to locate the center of the eye diagram. The different
eye diagrams will differ in voltage depending whether it is a transition bit or a de-emphasized
bit. The exact reduced voltage level of the de-emphasized bit will always be relative to the
transition bit.”
SDA-OM-E Rev H 363
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