General notes on working with imc CANSAS modules 125
imc CANSAS Users Manual - Doc. Version 1.9 - 05.12.2014© 2014 imc Meßsysteme GmbH
There, select the identifier for the message. This identifier must be unique for each module, just like
every identifier on the CAN-Bus in general. It is also possible to specify the interval at which the message
is sent. Intervals in the range between 1s and 10s would be sensible.
Contents of a Heartbeat-message (64 Bit)
serial number of the module (30 Bit)
1, if the module is in sync mode; 0 else
configuration number of the module (32 Bit)
3.5.10 Synchronization
With many imc CANSAS acquisition modules (modules which measure physical quantities and send CAN-
messages), there is the option to synchronize the data sampling of multiple modules.
Example: Each of a UNI8 module's channels is equipped with its own amplifier and A/D converter. All of
the module's channels are sampled simultaneously. However, if multiple UNI8 units are used, note that
each one has its own independent quartz timer. Therefore, the modules are not synchronized to each
other unless special steps are taken. If an application requires synchronized capture on more than 8
channels, the Synchronization feature can be used.
In imc CANSAS, synchronization can be achieved in a variety of ways.
CAN-1 Protocol: A CAN-Bus message is used for the synchronization. This message is sent at a 1s
pulse rate by a imc CANSAS-module acting as the Master. Other imc CANSAS-modules acting as
slaves receive this message and synchronize themselves to it. The message is formatted according
to the "CAN-1" protocol. In case devices as imc BUSDAQ and imc CRONOS-PL are used as CAN
logger, they should be set as CAN-1 Masters. This is the recommended option whenever these
devices also capture the measured data.
The condition for being able to perform synchronization via the CAN-Bus is that all the devices (both
the master and all slaves) are connected to the same CAN-Bus line, and no gateway or router may
be connected between them. In the CAN-1 protocol, special care is taken to provide high time-
precision.
If the imc CANSAS modules are configured by an imc device CAN interface through imc DEVICES
software, only the imc device is allowed to be set as CAN-1 master.
TTL square 1s: A line is laid between the imc CANSAS-modules on which communication by TTL-
level takes place. One of the imc CANSAS-modules is declared the Master and generates a 1 Hz
square-wave signal. Other imc CANSAS-modules are declared slaves. They respond to the signal by
getting into synchronization. The square-wave signal can also be generated by an external
generator. In all imc CANSAS-modules, one pin each in the CAN-Bus sockets is provided for the TTL-
signal. The signal's reference ground is the CAN-Bus ground which also has a terminal in the
connector. This arrangement enables the synchronization signal to be efficiently transferred along
the CAN-cable.
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