CP3BT23_14 Datasheet, PDF (136/324 Pages) Texas Instruments – CP3BT23 Reprogrammable Connectivity Processor with Bluetooth and Dual CAN Interfaces

CP3BT23
SNOSCX3A – JULY 2013 – REVISED JANUARY 2014
18.4 Acceptance Filtering
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Figure 18-15. Acceptance Filtering
Acceptance filtering of the incoming messages for the buffers 0...13 is performed by means of a global
filtering mask (GMASK) and by the buffer ID of each buffer. Acceptance filtering of incoming messages for
buffer 14 is performed by a separate filtering mask (BMASK) and by the buffer ID of that buffer.
Once a received object is waiting in the hidden buffer to be copied into a buffer, the CAN module scans all
buffers configured as receive buffers for a matching filtering mask. The buffers 0 to 13 are checked in
ascending order beginning with buffer 0. The contents of the hidden buffer are copied into the first buffer
with a matching filtering mask.
Bits holding a 1 in the global filtering mask (GMASK) can be represented as a “don’t care” of the
associated bit of each buffer identifier, regardless of whether the buffer identifier bit is 1 or 0.
This provides the capability to accept only a single ID for each buffer or to accept a group of IDs. The
following two examples illustrate the difference.
Example 1: Acceptance of a Single Identifier
If the global mask is loaded with 00h, the acceptance filtering of an incoming message is only determined
by the individual buffer ID. This means that only one message ID is accepted for each buffer.
GMASK1
00000000 00000000
GMASK2
00000000
00000
BUFFER_ID1
10101010 10101010
BUFFER_ID2
10101010
10101
10101010
Accepted ID
10101010 10101010
10101
DS033
Figure 18-16. Acceptance of a Single Identifier
136 CAN Module
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