CSS CANedge1, Руководство пользователя

Страница: 31 / 66

CANedge2 Docs, Release FW 01.04.02
Example: A message matches rejection filter 2. The following filters are not evaluated. The message is
rejected.
Example: A message does not match any filters. The message is rejected.
Filter method
Acceptance and Rejection filters can be defined by range or mask. In either case, both the message type
(standard / extended) and ID are compared to the filter.
Filter range method
With the Range method, the filter defines a range of IDs which are compared to the message ID. Message
IDs within the range (both start and end included) pass the filter.
Example: Standard ID filter with range from = 1, to = 10:
ID format ID (DEC) Pass
Standard 0 No
Standard 1 Yes
Standard 10 Yes
Standard 11 No
Extended 1 No
Filter mask method
With the Mask method, the filter defines an ID and Mask which are compared to the message ID.
A message passes a mask filter if the following condition is true
1
:
filter_id & filter_mask == message_id & filter_mask
Below a few examples to demonstrate the use of filters.
Example: Filter configuration which accepts one specific message ID: 2000
*
10 = 11111010000
2
. The
filter ID is set to the value of the message ID to accept. The filter mask is set to all ones, such that all
bits of the filter are considered, as given in (1).
Filter ID
Filter mask
Masked filter
11111010000
2
& 11111111111
2
11111010000
2
(1)
Message ID
Filter mask
Masked ID
11111010000
2
& 11111111111
2
11111010000
2
(2)
To test if the message passes the filter, we apply the filter mask to the message ID as given in (2). The
masked filter and the masked ID are equal - the message passes the filter.
1
&
is used as the bitwise AND operation
0.4. Configuration 27