IFM Electronic CR0451 - 9.3.2 Can Functions in the Iec User Cycle; CAN Functions in the IEC User Cycle; Processing of the Program Pous

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ifm System Manual ecomatmobile BasicDisplay (CR0451) V01
CAN in the PDM360 Exchange of CAN data
9.3.2 CAN functions in the IEC user cycle
Processing of the program POUs ................................................................................................80
POU inputs ...................................................................................................................................81
POU outputs.................................................................................................................................81
Libraries for CAN POUs ...............................................................................................................82
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INFO: IEC user cycle = PLC cycle in the CoDeSys application program.
The POUs of the external libraries are NOT executed during runtime of the IEC user cycle, but before
or afterwards. This means that the function blocks or the process variables are static during the IEC
user cycle seen from the point of view of the IEC programmer. Exempt from this are function blocks
with transmit function and FBs with FiFo function:
- CAN_TX...,  FBs for RAW-CAN (transmitting messages) (→ page 91
)
- CAN_RX_ENH_FIFO (→ page 106
)
- CAN_RX_RANGE_FIFO (→ page 102
)
INFO: FiFo (First In, First Out) = operation of the stack: the data package which was written into a
stack at first will be read at first too. For every identifier there is such one buffer (as a queue) available.
In fact, CAN stacks are also executed during the IEC user cycle, for example data is still transmitted
cyclically and multi-frame messages are still received. However, they will only be provided to the
application program after the IEC user cycle has elapsed.
INFO: CAN stack = stack of tasks for CAN data communication.
Processing of the program POUs
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Controlled processing of the program POUs is important. The operating system ensures the
following order:
 CAN_ENABLE
 J1939_ENABLE
 CANopen_ENABLE
 automatic start of the CANopen network based on the corresponding selection in the development
environment
 update process image for J1939 and CANopen
 other function blocks
Thus, when e.g. setting the baud rate a defined state on a system is achieved.
The baud rate which has been chosen for CAN_ENABLE is not supposed to be changed anymore by
any of the subsequent calls.
If CAN_ENABLE is set to FALSE and the CAN channel is thereby deactivated, all protocols will also
be reset.