Datasheet
20.6.2.5. Frame buffer receive mode
This mode is useful to receive multi frames. The priority between MObs offers a management for these
incoming frames. One set MObs (including non-consecutive MObs) is created when the MObs are set in
this mode. Due to the mode setting, only one set is possible. A frame buffer completed flag (or interrupt) -
BXOK - will rise only when all the MObs of the set will have received their dedicated CAN frame.
1. MObs in frame buffer receive mode need to be initialized as MObs in standard receive mode.
2. The MObs are ready to receive data (or a remote) frames when their respective configurations are
set (CONMOB).
3. When a frame identifier is received on CAN network, the CAN channel scans all the MObs in
receive mode, tries to find the MOb having the highest priority which is matching.
4. On a hit, the IDT, the IDE and the DLC of the matched MOb are updated from the incoming (frame)
values.
5. Once the reception is completed, the data bytes of the received message are stored (not for remote
frame) in the data buffer of the matched MOb and the RXOK flag is set (interrupt).
6. When the reception in the last MOb of the set is completed, the frame buffer completed BXOK flag
is set (interrupt). BXOK flag can be cleared only if all CONMOB fields of the set have been re-
written before.
7. All the parameters and data are available in the MObs until a new initialization.
20.6.3. Acceptance filter
Upon a reception hit (that is, a good comparison between the ID + RTR + RBn + IDE received and an IDT
+ RTRTAG + RBnTAG + IDE specified while taking the comparison mask into account) the IDT +
RTRTAG + RBnTAG + IDE received are updated in the MOb (written over the registers).
Figure 20-10. Acceptance filter block diagram.
CANIDM registers (MOb[i])
IDMSK
RTRMSK IDEMSK
CANIDT registers & CANCDMOB (MOb[i])
ID & RB
RTRTAG IDE
internal RxDcan
Rx Shift Register (internal)
ID & RB
RTR IDE
=
Hit MOb[i]
14(33)
13(31) - RB excluded
RB excluded
13(31)14(33)
Write
enable
13(31)
1
Examples:
Full filtering: to accept only ID = 0x317 in part A.
• ID MSK = 111 1111 1111
b
• ID TAG = 011 0001 0111
b
Partial filtering: to accept ID from 0x310 up to 0x317 in part A.
• ID MSK = 111 1111 1000
b
• ID TAG = 011 0001 0xxx
b
Atmel ATmega16M1/32M1/64M1 [DATASHEET]
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