Teledyne LeCroy SENT Decoder - Manual (Page 5)

Instruction Manual
922664 Rev A 3
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.