CP3BT23_14 Datasheet, PDF (137/324 Pages) Texas Instruments – CP3BT23 Reprogrammable Connectivity Processor with Bluetooth and Dual CAN Interfaces

CP3BT23
www.ti.com
SNOSCX3A – JULY 2013 – REVISED JANUARY 2014
Example 2: Reception of an Identifier Group
Set bits in the global mask register change the corresponding bit status within the buffer ID to “don’t care”
(X). Messages which match the non-“don’t care” bits (the bits corresponding to clear bits in the global
mask register) are accepted.
GMASK1
00000000 11111111
GMASK2
00000000
00000
BUFFER_ID1
10101010 10101010
BUFFER_ID2
10101010
10101
10101010
Accepted ID Group
XXXXXXXX 10101010
10101
DS034
Figure 18-17. Acceptance of a Group of Identifiers
A separate filtering path is used for buffer 14. For this buffer, acceptance filtering is established by the
buffer ID in conjunction with the basic filtering mask. This basic mask uses the same method as the global
mask (set bits correspond to “don’t care” bits in the buffer ID).
Therefore, the basic mask allows a large number of infrequent messages to be received by this buffer.
Note: If the BMASK register is equal to the GMASK register, the buffer 14 can be used the same way as
the buffers 0 to 13.
The buffers 0 to 13 are scanned prior to buffer 14. Subsequently, the buffer 14 will not be checked for a
matching ID when one of the buffers 0 to 13 has already received an object.
By setting the BUFFLOCK bit in the configuration register, the receiving buffer is automatically locked after
reception of one valid frame. The buffer will be unlocked again after the CPU has read the data and has
written RX_READY in the buffer status field. With this lock function, software has the capability to save
several messages with the same identifier or same identifier group into more than one buffer. For
example, a buffer with the second highest priority will receive a message if the buffer with the highest
priority has already received a message and is now locked (provided that both buffers use the same
acceptance filtering mask).
As shown in Figure 18-18, several messages with the same ID are received while BUFFLOCK is enabled.
The filtering mask of the buffers 0, 1, 13, and 14 is set to accept this message. The first incoming frame
will be received by buffer 0. Because buffer 0 is now locked, the next frame will be received by buffer 1,
and so on. If all matching receive buffers are full and locked, a further incoming message will not be
received by any buffer.
Received ID 01010
GMASK 00000
10101010 10101010 10101010
11111111 00000000 00000000
BUFFER0_ID 01010
XXXXXXXX 10101010 10101010
BUFFER1_ID 01010
BUFFER13_ID 01010
XXXXXXXX 10101010 10101010
XXXXXXXX 10101010 10101010
Saved when buffer
is empty
Saved when buffer
is empty
Saved when buffer
is empty
BMASK 00000
11111111 00000000 00000000
BUFFER14_ID 01010
XXXXXXXX 10101010 10101010
Saved when buffer
is empty
DS035
Figure 18-18. Message Storage with BUFFLOCK Enabled
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