Teledyne LeCroy Line Code and Symbolic Decoders - Manual (Page 4)

Line Code and Symbol Decoders
2 922663 Rev A
Introduction
About This Manual
Teledyne LeCroy offers different toolsets for decoding and debugging serial data streams. These toolsets
may be purchased as optional software packages, or are provided standard with SDA and DDA model
oscilloscopes.
This Line Code and Symbol Decoders Instruction Manual explains how to use the following toolsets:

NRZ Configurable Decoder

Manchester Configurable Decoder

8b/10b Decoder

64b/66b Decoder
Assumptions
This manual is presented with the assumption that:

You have a basic understanding of the various serial data standard physical and protocol layer
specifications, and know how these standards are used in embedded controllers.

You have a basic understanding of how to use an oscilloscope, and specifically the Teledyne
LeCroy oscilloscope on which the serial trigger and decode option is installed. Only features
directly related to serial data decode are explained in this manual; please see the oscilloscope
online Help file, Operator's Manual, or Getting Started Manual for other instructions.

You have purchased and installed one of optional serial data decoders described in this manual.
Compatibility
Teledyne LeCroy is constantly expanding coverage of serial data standards and updating software. Some
capabilities covered in this documentation may only be available with the latest version of our firmware.
You can download the firmware update from teledynelecroy.com.
While some of the screen images in this manual may not exactly match what is seen on your
oscilloscope display—or show an example taken from your protocol—be assured that the functionality is
nearly identical, as much functionality is shared.
Serial Decode Technical Overview
The algorithms described here at a high level are used by all Teledyne LeCroy serial decoders sold for
oscilloscopes. They differ slightly for serial data signals that have a clock embedded in data or a clock
separate from data. See the Overview for each encoding scheme later in this manual for more specific
information.
The first software algorithm examines the embedded clock for each message based on a default (or user
specified) vertical level. Once the clock signal is extracted or known, the algorithm examines the
corresponding data signal at a predetermined vertical level to determine whether a data bit is high or
low. The default vertical level is usually set to 50% and is determined from a measurement of peak
amplitude of the signals acquired by the oscilloscope. It can also be set to an (absolute) voltage level, if
desired. The algorithm intelligently applies a hysteresis to the rising and falling edge of the serial data
signal to minimize the chance of perturbations or ringing on the edge affecting the data bit decoding.