Menu functions 101
imc CANSAS Users Manual - Doc. Version 1.9 - 05.12.2014© 2014 imc Meßsysteme GmbH
3.4.4.8 Module - Calculate Bus load
This command can be used to compute the aggregate load of all modules selected.
Example:
The signals of 8 channels having 16 bits apiece are sent in 2 messages at one node at a Baud rate of
1MBit.
This results in 8 Bytes or 64 sits of payload data per message. Including interframe space, this results in
109 bits per message, of which 99 bits are subject to the stuff-bit rule.
The messages are sent at a data rate of 1kHz.
The Stuff-Bit rule stipulates: If five consecutive bits have the same state, one bit of the opposite state is
inserted into the data stream. Depending on the data, these stuff-bits are inserted either frequently or
rarely. Since this cannot be predicted, it is necessary to assume the worst case (longest message).
The resulting message length is thus:
109 bits + 0.2 * (99 bits) = 109 bits + 20 bits = 129 bits
Since there are two messages -> 258 bits
With a data rate of 1 kHz, this means: 258 bits *1000/s = 258000 bits/s
In reference to the node’s Baud rate: 258KBit/1000kBit= 25.8%
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