Configuration via SIMATIC Manager
CAN-CBM-DP
Software Manual Rev. 2.0
36
Command 3: Reception on enabled Rx-identifiers
The reception of data requires the CAN-Rx-identifiers which are to receive data to be
enabled (see command 4).
After reception command 3 has been written, read accesses to the Communication
Window will give you the data structure shown on page 34. The Rx-data is received
asynchronously to the PLC-cycle. Until valid data has been received you will be returned
the value ‘EEEE’ hex in the first bytes in read accesses. Only after valid data has been
received the Rx-identifier of the read frame in the first bytes becomes readable. In
addition, the read command which requested the reception of data is assigned by means of
the returned PLC-loop counter in byte 13.
The module has got a FIFO-memory for 255 CAN-frames to buffer the received Rx-data.
If several Rx-frames are to be received on one Rx-identifier, or if frames of various Rx-
identifiers enabled for reception are received, the data is not lost, as long as the PLC reads
out the FIFO memory quicker than it is being filled.
Command 4: Enabling Rx-identifiers for reception
By means of this command the Rx-identifier whose data is to be received has to be
enabled. More than one Rx-identifier can be enabled at the same time. For this, the
command has to be called an according number of times.
Command 5: Deactivate reception (command 4)
After this command has been called no data is received any longer on the specified Rx-
identifiers.
Command 6: Sending an RTR-frame
By means of this command a remote-request frame is transmitted. Prior to the
transmission the reception on the Rx-identifier has to be enabled by command 4.
Command 7: Executes command 4 and command 6
See there.
