HBM SOMATXR, Руководство по эксплуатации, Страница: 33 / 152

Functional description
CANBus
A4461-2.0 HBM: public
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6.4 CAN decoder: receiving CAN data
6.4.1 Remote frames (RTR)
A CAN master transmits remote frames to promptly
request data. None of the MX module types support
remote frames (RTR). These messages are discarded
when received.
6.4.2 User-defined data type selection
The CAN decoder constantly distinguishes between the
data format in which data are extracted from the CAN
message and the data format in which they are available
as a signal in the QuantumX / SomatXR system. The
CAN decoder behaves differently, depending on the com­
bination of the two data types. This may seem confusing
at first, but it allows integer values to constantly be han­
dled as such, so that the processing of the digital I/O
data is not corrupted and the floating point calculations
are as accurate as possible.
Once the data bytes have been received by the CAN
bus, they are handled as the raw data type, as specified
in the parameterization (“RawValueFormat”). The signal
that will later be used throughout the system is defined
by the output format (“SignalFormat”). The integer data
types will also be checked to establish whether they are
signed (INT32 and INT64) or not (UINT32 and UINT64).
The data type for interpreting the mode-dependent signal
is always assumed to be UINT64. The mode length can
be selected between 1 and 64. It is not possible to scale
the “ModeValue”; nor does there seem to be any point to
doing so.