© 2004 Microchip Technology Inc. DS70070B-page 23-43
Section 23. CAN
CAN Module
23
Table 23-4: Acceptance Filter
The DBEN bit (CiRX0CON<2>) allows the FILHIT bits to distinguish a hit on filter RXF0 and
RXF1 in either RXB0 or overrun into RXB1.
111 = Acceptance Filter 1 (RXF1)
110 = Acceptance Filter 0 (RXF0)
001 = Acceptance Filter 1 (RXF1)
000 = Acceptance Filter 0 (RXF0)
If the DBEN bit is clear, there are 6 codes corresponding to the 6 filters. If the DBEN bit is set,
there are 6 codes corresponding to the 6 filters plus 2 additional codes corresponding to RXF0
and RXF1 filters overrun to RXB1.
If more than 1 acceptance filter matches, the FILHIT bits will encode the lowest binary value of
the filters that matched. In other words, if filter 2 and filter 4 match, FILHIT will code the value for
2. This essentially prioritizes the acceptance filters with lower numbers having priority.
Figure 23-10 shows a block diagram of the message acceptance filters.
Figure 23-10: Message Acceptance Filter
FILHIT<2:0> Acceptance Filter Comment
000
(1)
RXF0 Only if DBEN = 1
001
(1)
RXF1 Only if DBEN = 1
010 RXF2 —
011 RXF3 —
100 RXF4 —
101 RXF5 —
Note 1: Is only valid if the DBEN bit is set.
Acceptance Filter Register Acceptance Mask Register
RxRqst
Message Assembly Buffer
RXFn0
RXFn1
RXFnn
RXMn0
RXMn1
RXMnn
Identifier
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