CONTROLLER AREA NETWORK (bxCAN)
CONTROLLER AREA NETWORK (Cont’d)
Figure 150. Filtering Mechanism - example
Message Received
Data
Identifier
Ctrl
Receive FIFO
Identifier
Identifier
Identifier
0
1
2
Message
Stored
Identifier #2 Match
Identifier
n
Identifier
Mask
n+1
n+m
Identifier
Mask
No Match
Found
n: number of single identifiers to receive
m: number of identifier groups to receive
n and m values depend on the configuration of the filters
Message Discarded
The example above shows the filtering principle of
the bxCAN. On reception of a message, the iden-
tifier is compared first with the filters configured in
identifier list mode. If there is a match, the mes-
sage is stored in the associated FIFO and the in-
dex of the matching filter is stored in the Filter
Match Index. As shown in the example, the identi-
fier matches with Identifier #2 thus the message
content and MFMI 2 is stored in the FIFO.
If there is no match, the incoming identifier is then
compared with the filters configured in mask
mode.
If the identifier does not match any of the identifi-
ers configured in the filters, the message is dis-
carded by hardware without disturbing the soft-
ware.
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