Instruction
Manual
SENT Decoder
SENT Decoder Instruction Manual
© 2013 Teledyne LeCroy, Inc. All rights reserved.
Unauthorized duplication of Teledyne LeCroy documentation materials other than for internal sales and
distribution purposes is strictly prohibited. However, clients are encouraged to distribute and duplicate
Teledyne LeCroy documentation for their own internal educational purposes.
SENT and Teledyne LeCroy are registered trademarks of Teledyne LeCroy, Inc. Windows is a registered
trademark of Microsoft Corporation. Other product or brand names are trademarks or requested
trademarks of their respective holders. Information in this publication supersedes all earlier versions.
Specifications are subject to change without notice.
922664 Rev A
March 2013
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TABLE OF CONTENTS
Introduction .................................................................................................................. 2
About This Manual .................................................................................................................. 2
SENT Overview ........................................................................................................................ 2
Serial Decode Technical Overview .......................................................................................... 3
General Approach .................................................................................................................... 4
Setting Up the Decoder .................................................................................................. 5
Verify Bit-Level Decode ........................................................................................................... 7
Enable/Disable Decoder .......................................................................................................... 7
Working with the Decoded Waveform ............................................................................ 8
Serial Decode Annotations ...................................................................................................... 8
Search Waveform .................................................................................................................... 9
Working with the Result Table ..................................................................................... 10
Customize Decode Result Table ............................................................................................ 10
Export Decode Result Table .................................................................................................. 11
Teledyne LeCroy Service Centers .................................................................................. 12
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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 manual explains how to use the SENTtoolset.
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.
SENT Overview
SAE J2716 SENT (Single Edge Nibble Transmission) protocol is a point-to-point scheme for transmitting
signal values from a sensor to a controller. It is intended to allow for high-resolution data transmission
with a lower system cost than available serial data solution. Data are transmitted in units of 4 bits = 1
nibble for which the interval between two falling edges (single edge) of the modulated signal with a
constant amplitude voltage is evaluated. A data frame contains 24 bits of data (each 3 nibbles for 2
channels, such as pressure and temperature), 4 bits = 1 nibble for error detection (CRC) and 4 bits = 1
nibble of status and communication, making a total of 8 nibbles. Optionally, data can be transferred in a
5-nibble frame, with 3 nibbles for a single measurement channel, 1 for CRC and 1 for the
status/communication. (SENT Protocol, wikipedia.org, accessed 03-06-2013).
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The Teledyne LeCroy SENT decoder option is a tool aimed at decoding SENT streams emitted by various
sensors. This decoder supports both the 2008 and the 2010 SENT specification through user-selectable
variables.
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.
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.
NOTE: Although the decoding algorithm is based on a clock extraction software algorithm using a
vertical level, the results returned are the same as those from a traditional protocol analyzer using
sampling point-based decode.
After determining individual data bit values, another 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.
Finally, another algorithm applies a color overlay with annotations to the decoded waveform to mark
the transitions in the signal. Decoded message data is displayed in tabular form below the grid. 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.
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General Approach
The order of your interaction with the decoder software in many ways mirrors the order of the
algorithms. You will:
Assign a protocol/encoding scheme, an input source, and a clock source (if necessary) to one of
the four decoder panels using the Serial Data and Decode Setup dialogs.
Complete the remaining dialogs required by your protocol/encoding scheme to decode
Transitions, Bits and Words.
Work with the decoded waveform and result table to analyze the decoded data.
While not required, we recommend the following general approach to decoding:
1. Set up the decoder.
2. Acquire a single burst of relevant data, then run the decoder.
NOTE: If the sampling rate (SR) is insufficient to resolve the signal adequately based on the bit rate
(BR) setup or clock frequency, the protocol decoding is turned OFF to protect you from incorrect
data. The minimum SR:BR ratio required is 4:1. It is suggested that you use a slightly higher SR:BR
ratio if possible, and use significantly higher SR:BR ratios if you want to also view perturbations or
other anomalies on your serial data analog signal.
3. Use the various analysis tools to verify that transitions are being correctly decoded. Tune the
decoder settings as needed.
4. Run the decoder on acquisitions of the desired length.
You can disable/enable the decoder as desired without having to repeat the set up and tuning
provided the basic signal characteristics do not change.
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Setting Up the Decoder
You can preset up-to-four, independent decoders using the same or different protocols and data
sources. These decoders can be enabled simultaneously or separately, and for each you can select what
data appears on the display.
1. Touch the Front Panel Serial Decode button (if available on your oscilloscope), or choose Analysis >
Serial Decode from the oscilloscope menu bar to access the Serial Decode dialogs.
2. On the same row as the Decoder #:
Select the desired Protocol to use. The selections will depend on the software options
installed on your instrument.
Select the Source (Data) to be decoded. This can be any signal input channel, memory, or
math function. Depending on your Protocol selection, you may be required to select more
than one source. The requisite number of fields will automatically appear.
3. Touch the Setup button to open the Decode Setup dialog. If you use this method rather than the
tab, the correct decoder will be selected by default.
4. Go on to complete the settings required for the SENT protocol.
TIP: You can quickly start setup for the other decoders by using the Decode # buttons at the left of the
Decode Setup dialog. You don't have to step back to the Serial Decode dialog to start the setup. Controls
with the same label on either dialog share the same function.
Basic Dialog - SENT
Configure all settings on the Basic right-hand dialog:
Decode Type - Choose whether to decode Nibbles or Words in the source signal.
Channels - Choose to decode Fast Only, Slow Only, or Both channels.
Format - Choose to decode results in Hex(idecimal) or Dec(imal) format.
TickTime - Time in seconds between a nibble of value N and a nibble of value N+1.
TickTime Tol(erance) - Defines how the CAL pulse is filtered with respect to the Ticktime indicated by
the user. i.e. if a tick Time of 3us is set, with a tolerance of 10% the CAL pulse is expected to be 56 * 3 us
+- 10%, therefore 168 us +- 10%..
Idle State - Defines where the idle state lies, therefore opposite of pulse direction. Choose IdleLow or
IdleHigh.
Nibbles - Enter number of nibbles that make up a word. Choose 8 or 5 (8 is the default).
Version - Choose the version of the protocol used in the decoded signal. If you are using the Jan 2010
version, also choose to enable or disable the following Protocol Details:
New CRC - When checked, the CRC computation will be performed as per 2010 recommended
implementation under 5.4.2.2. Otherwise it will follow the 2008 guidelines, under 5.4.2.1
(Legacy).
Pause Pulse - When checked, algorithm expects a Pause pulse as per 2010 definition under 5.2.6.
The Pause Pulse follows the CRC of message N and precedes the CAL pulse of message N+1.
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Fast Channel Dialog
Within the Basic dialog, the Fast Channel tab will appear if you select Decode Type “Words” and
Channels is set to either “Fast” or “Both.”
Within the Fast Channel dialog, this SENT decoder has four user defined data fields, D0 through D3. Each
of these can be used to present the content of the message payload as it was programmed. Start by
selecting the payload offset, then specifying where in the data field and how many nibbles are included.
For each of the four data bits (D0-D3) that are in use, specify the payload interpretation.
Active - check to activate the display showing payload content.
Offset - Defines where in the payload you start including content.
Nibbles – Number of nibbles included in the displayed value.
Order – data can be presented in least-significant bit or most-significant bit order.
Slow Channel Dialog
Within the Basic dialog, the Slow Channel tab will appear if you select Decode Type “Words” and
Channels is set to either “Slow Only” or “Both.” The Slow Only option takes a single data value from
each of 16 or 18 SENT message packets and build a resulting Slow Channel result, displayed within the
decoded table.
A Slow Channel Definition File (SCDF) is used to decode this data into a more meaningful presentation of
the assimilated slow channel data. Within the Slow Channel dialog controls, use the navigation controls
to select the user defined text table file for this purpose.
To download the data file, connect a USB drive one of the oscilloscope host USB ports and navigate to
the directory. We recommend that you build your library of these text files at this location:
C:\LeCroy\XStream\Applications\SENT
Levels Dialog
The Levels dialog controls the levels used for determining the edge crossings of the SENT signal. The
default settings of Percent level = 25% and Hysteresis = 0.5 divisions are usually appropriate for most
signals.
Level Type - whether Level will be given as Percentage of amplitude or Absolute number of vertical
divisions.
Level - percentage of amplitude or absolute voltage at which the crossing occurs.
Hysteresis Type - whether Hysteresis will be given as Percentage or absolute number of vertical
Divisions.
Hysteresis - margin of error; amount signal may rise or fall without affecting bit transition.
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Verify Bit-Level Decode
When all Basic dialog values are set, you should already see a basic bit-level decoding on the selected
source trace. The Data Mode is set to bits by default, so that the remaining protocol-specific settings do
not matter for the initial bit-level decode.
In a correct bit-level decoding, bit transitions are all aligned with signal transitions, and the logical
interpretation of the bits is consistent with the physical level.
Review your decoded waveform for instances of incorrect bit-level decoding, particularly:
Decoding at an exact multiple of the Bit Rate that would not allow further interpretation of the
words
Bits not aligned with the transitions
Bit stream with gaps between the bits
Enable/Disable Decoder
Once preset, the four decoders can be enabled simultaneously or separately as often as you wish,
although this number may be limited depending on the type of source channels selected. Preset
decoders can be easily disabled without disrupting the configuration.
To enable:
Press the Front Panel Serial Decode button, or choose Analysis > Serial Decode, to open the Serial
Decode dialog, then check Decode On next to the respective decoder.
If View Decode is checked (default) on the Decode Setup dialog, a result table and decoded waveform
appears for each enabled decoder. The number of rows of data displayed on each table will depend on
the Table#Rows setting. The default is one, which can be increased, but doing so will decrease the
amount of the screen available to display traces.
To disable:
Deselect the Decode On box individually, or touch Turn All Off.
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Working with the Decoded Waveform
Serial Decode Annotations
When a decoder is enabled, an annotated waveform showing the decoder results appears on the
oscilloscope display.
A colored overlay marks significant transitions in the source signal. The overlay contains annotations
corresponding to the data itself, any pre/post-message padding, inter-burst periods, etc. Each set of
annotations is customized to the protocol or encoding scheme.
The information shown on a given annotation is affected by the width of the rectangles in the overlay,
which is determined by the magnification (scale) of the trace and the length of the acquisition. If the
rectangles are:
< 10 pixels wide, no annotation is shown.
> 10 but < 100 pixels wide, only the short form of the names appear.
> 100 but < 500 pixels wide, the long form name and number of repetition appears
> 500 pixels, all details appear.
These overlays appear on the source trace or its zoom trace to highlight key portions of the decoded
signal.
Inter Frame Gap - Green overlay indicating period between bursts.
Burst - Navy overlay indicating period of burst (data frame).
Synchro - Grey overlay to left of status showing synchronization timeout value.
Status - Bright purple overlay to left of data, showing status and communication bits.
Data - Bright aqua overlay, indicating payload data.
Decoded waveform. At this resolution, very little information appears on the overlay.
Zoomed waveform annotations, showing decode data.
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Search Waveform
Choosing Search on the Decode Setup dialog opens a Zoom of the original decoded waveform and
displays the corresponding Zoom dialog with the standard rescaling controls.
Use the Zoom dialog Rescale controls to reposition the Zoom trace; use the Search dialog controls to
enter the search criteria.
Configure the following to specify the search criteria for SENT decodes:
Column to Search - Result table column to search for values.
Left/Right Pad - Percentage of horizontal division surrounding a found item to display.
Use the navigation buttons to find the next event that matches your search criteria:
Prev(ious) navigation buttons (top to bottom): go to previous occurrence of field or value; go to first
matching occurrence of field or value; scroll decoded signal from current point to beginning of decode;
pause scrolling.
Next navigation buttons(top to bottom): go to next occurrence of field or value; go to last matching
occurrence of field or value; scroll decoded signal from current point to end of decode; pause scrolling.
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Working with the Result Table
By default, a table summarizing the decoder results appears below the grids. The decode results table
provides a view of message data as decoded by the oscilloscope during the most recent acquisition,
even when messages are too compact to allow annotation on the waveform trace.
The table is displayed only when the View Decode checkbox is marked on the Decode Setup Dialog and
a source signal has been decoded using that protocol.
Typical serial data decode results table
The first column heading (top left most cell of the table) bears the name of the corresponding protocol,
and the cell's fill color matches the color of the input source. Touching this cell opens the Decode Setup
dialog if it has been closed.
Touching a particular row of the table opens a Zoom of the corresponding point in the decode trace.
The result table is customizable. Keep in mind that displaying several multiple-row tables will reduce the
amount of screen space available for the waveform grids.
You can also export result table data to a .CSV file.
Customize Decode Result Table
Follow these steps to change which decode values appear in the result table:
1. Press the Front Panel Serial Decode button, or choose Analysis > Serial Decode, then open the
Decode Setup tab.
2. Touch the Configure Table button.
3. On the View Columns pop-up dialog, check boxes for the columns you want to appear in the table.
Clear boxes for any columns you wish to remove. Only those columns selected will appear on the
oscilloscope display.
To return to the preset display, touch Default.
4. Optionally, set a BitRate Tolerance percentage. This value will allow for signal jitter correction while
decoding.
5. Touch the Close button when finished.
6. Optionally, on the Decode Setup dialog enter the Table # Rows to display. Each row will contain data
from one decoded message.
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You may display these columns on a SENT result table:
Idx - Index of the line in the table, also number of the message in the annotation overlay on the trace.
Time(us) - Time (in microseconds) of the beginning of the SENT burst, with respect to the trigger point of
the record.
Sync - Real Measured Length of the Sync Pulse. The pulse width is measured between the two falling
edges of the Sync pulse, at the intersection of the signal and the Level selected in the Level Tab. Note
that a large hysteresis will impact this value.
D0 - Reserved for special applications.
IFG - Inter Frame Gap, measured from the end of a burst to the beginning of the next burst.
Msg (always shown) - Message summary, with the number of transitions, nibbles and words.
Tck - TickTime; value of the SYNC pulse divided by 56.
Status (1) (always shown) - Value of the status and communication nibbles. This value is split into its
component bits in the next four columns to help interpret the contents.
b0 - Reserved for special applications.
b1 - Reserved for special applications.
b2 - Serial Data Message Bits (slow channels).
b3 - Message Start.
crc (always shown) - Value of the CRC (error detection) nibble compared to values of the other nibbles
of the message. If it does not match, an Error appears in the Status (2) column. It is normal that the first
and last messages of a record, when truncated, generate a crc error.
rms (always shown) - Root Mean Square value of the falling edge crossings, usually in nanoseconds.
Status (2) - reported Errors and Warnings.
Export Decode Result Table
You can export the decode result table data to a .CSV file.
Export files are by default created in the Xstream\Applications\<protocol> folder, although you can
choose any other folder on the oscilloscope, or any external drive connected to a host USB port. The
data will overwrite the last export file saved in the protocol directory, unless you enter a new filename.
To export the result table:
1. Press the Front Panel Serial Decode button, or choose Analysis > Serial Decode, then open the
Decode Setup tab.
2. Optionally, touch Browse and enter a new File Name and output folder.
3. Touch the Export Table button.
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922664 Rev A
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