Teledyne LeCroy Serial Data Debug Solutions - Manual (Page 12)

Serial Data Debug Solutions
12 919586 RevA
Accessing and Using Supported Protocol Toolsets
Accessing and Using Supported Protocol Toolsets Overview
LeCroy's various serial data debug solutions utilize advanced trigger circuitry and advanced software algorithms
to provide powerful capability for serial data triggering, decoding, and analysis. The various software options are
accessed in the user interfaces in different ways. Some options are provided with certain oscilloscope models;
others are purchased and installed.
PLEASE NOTE THE FOLLOWING:

This section of the manual is meant to provide an initial explanation as to how the different toolsets are
accessed and used with some technical explanations at the end of the section. The information is
provided in this fashion to illustrate the commonality among toolset usage across supported protocols.

Since each serial protocol is quite different, serial trigger conditions and other settings for supported
protocols are also different. Detailed information as to how a serial trigger conditions is set up for a
specific supported protocol is covered in corresponding sections of this manual for each option. Ask your
local LeCroy representative for more information about any Serial Data Debug Solution Protocols or
Toolkits using the Contact LeCroy for Support (on page 199) topic.
The D and TD Toolsets
Technical Explanation of Serial Decode and Trigger
S ERIAL D ECODE
Both the D and TD options contain powerful protocol decoding and annotation software algorithms. This
algorithm is used in all LeCroy serial decoders sold with oscilloscopes, and differs slightly for serial data signals
that have a clock embedded in data or a clock separate from data.
The software algorithm examines the embedded clock (see Serial Data Debug Solutions (on page 9) for
synchronous/asynchronous protocol details) for each message based on a default (or user set) 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.
After determining individual data bit values, a different algorithm performs a decoding of the serial data
message after separation of the underlying data bits into logical groups (Header/ID, Data Length Codes, Data,
CRC, Start Bits, Stop Bits, etc.) specific to the protocol. Once the clock signal is acquired and the decoding is
completed for a serial data message with separate clock and data lines, the oscilloscope channel showing the
capture clock signal can be turned OFF to reduce screen clutter.
Finally, another algorithm provides the appropriate color coding of the message, and displays the protocol
message data on the screen, as desired, overlaid on the source trace. Various compaction schemes are utilized
to show the data during a long acquisition (many hundreds or thousands of serial data messages) or a short
acquisition (one serial data message acquisition). In the case of the longest acquisition, only the most important
information is highlighted. In the case of the shortest acquisition, all information is displayed (Header/ID, Data
Length Codes, Data, CRC, Start Bits, Stop Bits, etc.) with additional highlighting of the complete message frame.