CANoe DENoe - KEMT FEI TUKE

9.5 Original timestamp
169
This is the original timestamp generated by the MOST hardware. Only the unit is
changed to 10 µs and an offset is subtracted, so that the measurement start again
has approximately a timestamp of 0.
For higher precision use this timestamp for calculations concerning periods of time
only in the MOST system on one channel. The offset between original timestamps
from different MOST channels may vary with each measurement start. But provided
that the MOST channels are derived from a single MOST ring, the offset stays constant
during the measurement, due to the synchronization of the MOST devices to
the timing master in the ring.
If different MOST channels of CANoe are connected to different MOST rings (with
different timing masters) each MOST channel has its own time base. The original
timestamps will diverge in this case. Therefore the MOST channels are also synchronized
which will affect only the synchronized timestamp.
9.6 Time Synchronization Accuracy
The accuracy of the synchronization between MOST channels is typically +/- 1 ms,
between a MOST and a CAN channel is around +/- 2 ms.
These statements are based on measurements with a desktop PC with a Pentium III
450 MHz, Windows NT 4.0 (SP6) and a CANcardX with driver version 3.0. The Optolyzer
boxes were operated in spy mode with a continuous bus load of up to
166 frames/s. (With more than 166 frames/s the buffer of the Optolyzer box starts to
fill up). The CAN bus was operated with two active channels at 1 MBit/s and a busload
of 30 % on each channel.
Due to adaptive algorithms the full accuracy of the synchronization is achieved only
after a few seconds after measurement start. If synchronization is a critical point
within the measurement application, start the measurement a couple of seconds before
the condition which shall be analyzed occurs.
If CANoe is used to trigger the interesting condition on the bus, use interactive triggering
e.g. by operating a panel or an interactive generator block or use a CAPL
timer started at measurement start to allow a delayed trigger condition.
9.7 Database Support
CANoe.MOST offers two ways of describing the data structure on the MOST frames.
Known from version 0.95 is the description of messages in a CANdb++ database.
This is still the only way to have database support for MOST in CAPL. In CAPL, messages
can be identified and parameters can be accessed by names defined in the
CANdb++ database. Additionally this way is used to show parameter values in the
Data and Graphics Windows and to statically translate physical addresses into device
names.
Unfortunately the CANdb++ database does not allow the description of all data formats
used in MOST systems.
© Vector Informatik GmbH CANoe/DENoe Manual Version 4.1.1