Port And Attribute Names; Comma Definition; Jitter Definition; Total Jitter (Dj + Rj) Definition - Xilinx Virtex-4 RocketIO User Manual

Preface: About This Guide

Port and Attribute Names

All input and output ports of the RocketIO transceiver primitives are denoted in upper-
case letters. Attributes of the RocketIO transceiver can be denoted in upper-case letters
with underscores or all upper-case letters.
When assumed to be the same frequency, RXUSRCLK and TXUSRCLK are referred to as
USRCLK and can be used interchangeably. This also holds true for RXUSRCLK2,
TXUSRCLK2, and USRCLK2.

Comma Definition

A comma is a "K" character used by the transceiver to align the serial data on a
byte/half-word boundary (depending on the protocol used), so that the serial data is
correctly decoded into parallel data.

Jitter Definition

Jitter is defined as the short-term variations of significant instants of a signal from their
ideal positions in time (ITU). Jitter is typically expressed in a decimal fraction of Unit
Interval (UI), for example, 0.3 UI.

Total Jitter (DJ + RJ) Definition

•
•

MGT Definition

The term MGT refers to the Virtex-4 RocketIO Multi-Gigabit Transceiver. Previous
generations are explicitly called out: Virtex-II Pro RocketIO or Virtex-II Pro X RocketIO X.
30
Deterministic Jitter (DJ) – DJ is data pattern dependant jitter, attributed to a unique
source (for example, Inter Symbol Interference (ISI) due to loss effects of the media).
DJ is linearly additive.
Random Jitter (RJ) – RJ is due to stochastic sources, such as thermal and flicker noise,
and so on. RJ is additive as the sum of squares and follows a normal distribution.
www.xilinx.com Virtex-4 RocketIO MGT User Guide
UG076 (v4.1) November 2, 2008
R