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6.6. Description of the CAN function blocks
The CAN function blocks for use in the application program will
be described below.
To utilize the full functions of CAN it is absolutely required for
the programmer to create a precise bus concept before starting
to work. The number of the data objects with their identifiers
must be defined as well as a reaction to possible CAN errors.
Also, the frequency with which data must be transmitted has to
be taken into account. So the functions CAN_TRANSMIT and
CAN_RECEIVE must be called just as frequently. The
programmer must additionally monitor whether his transmission
orders have been passed on successfully to CAN_TRANSMIT
(bit RESULT) or must make sure that the data received are read
from the data buffer of the queue with CAN_RECEIVE and are
immediately processed in the program.
To be able to set up a communication link the same
transmission rate (baud rate) must first be set for all participants
of the CAN network. For the R 360 this is done with the function
CAN_BAUDRATE.
Example program
An example program in function block diagram (FBD) is stored
on the program diskette ecolog 100
plus
(CAN 3_66.PRO). In this
example data objects are exchanged with another CAN
participant via the identifiers 1 and 2. To do so, the other
participant must have a receive identifier for the transmit
identifier (or vice versa).
The function CAN_ACCEPTANCE is not further described here
because the application requires thorough hardware knowledge
of the CAN controller. Users who need this special feature are
requested to contact the technical support.
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