MEGA128CAN Datasheet, PDF (239/413 Pages) ATMEL Corporation – Microcontroller WITH 128K BYTES OF ISP FLASH AND CAN CONTROLLER

Acceptance Filter
MOb Page
4250E–CAN–12/04
AT90CAN128
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 com-
pleted 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.
Upon a reception hit (i.e., 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 120. Acceptance Filter Block Diagram
internal RxDcan
Rx Shift Register (internal)
ID &RB
RTR IDE
13(32)
=
13(32)
Write
Enable
13(32)
ID &RB
RTRTAG IDE
CANIDT Registers & CANCDMOB (MOb[i])
13(32)
Hit MOb[i]
1
13(32)
IDMSK
RTRMSK IDEMSK
CANIDM Registers (MOb[i])
Note:
Examples:
To accept only ID = 0x317 in part A.
- ID MSK = 111 1111 1111 b
- ID TAG = 011 0001 0111 b
To accept ID from 0x310 up to 0x317 in part A.
- ID MSK = 111 1111 1000 b
- ID TAG = 011 0001 0xxx b
Every MOb is mapped into a page to save place. The page number is the MOb number.
This page number is set in CANPAGE register. The number 15 is reserved for factory
tests.
CANHPMOB register gives the MOb having the highest priority in CANSIT registers. It is
formatted to provide a direct entry for CANPAGE register. Because CANHPMOB codes
CANSIT registers, it will be only updated if the corresponding enable bits (ENRX, ENTX,
ENERR) are enabled (c.f. Figure 124).
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