CP3BT23 Datasheet, PDF (104/260 Pages) Texas Instruments – CP3BT23 Reprogrammable Connectivity Processor with Bluetooth and Dual CAN Interfaces

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 ex-
ample, 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 49, 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 mes-
sage. The first incoming frame will be received by buffer 0.
Because buffer 0 is now locked, the next frame will be re-
ceived 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
Saved when buffer
BUFFER1_ID 01010 XXXXXXXX 10101010 10101010
BUFFER13_ID 01010 XXXXXXXX 10101010 10101010
is empty
Saved when buffer
is empty
Saved when buffer
is empty
BMASK 00000
11111111 00000000 00000000
te ^{BUFFER14_ID 01010 XXXXXXXX 10101010 10101010}
Saved when buffer
is empty
DS035
Figure 49. Message Storage with BUFFLOCK Enabled
le ^{18.5 RECEIVE STRUCTURE}
All received frames are initially buffered in a hidden receive
buffer until the frame is valid. (The validation point for a re-
ceived message is the next-to-last bit of the EOF.) The re-
ceived identifier is then compared to every buffer ID
together with the respective mask and the status. As soon
o _{as the validation point is reached, the whole contents of the}
hidden buffer are copied into the matching message buffer
as shown in Figure 50.
Note: The hidden receive buffer must not be accessed by
the CPU.
Buffer 0
BUFFER_ID
s _CR16CAN
Hidden
Receive
Buffer
Buffer 13
BUFFER_ID
b _Buffer14
O ^BUFFER_ID
DS036
Figure 50. Receive Buffer
The following section gives an overview of the reception of
the different types of frames.
The received data frame is stored in the first matching re-
ceive buffer beginning with buffer 0. For example, if the mes-
sage is accepted by buffer 5, then at the time the message
will be copied, the RX request is cleared and the CAN mod-
ule will not try to match the frame to any subsequent buffer.
103
www.national.com