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17.4 Acceptance Filtering Function and Masking Function
These functions serve the users to select and receive a facultative message. The C0GMR register, the
C0LMAR register, and the C0LMBR register can perform masking to the standard ID and the extended ID
of 29 bits. The C0GMR register corresponds to slots 0 to 13, the C0LMAR register corresponds to slot 14,
and the C0LMBR register corresponds to slot 15. The masking function becomes valid to 11 bits or 29 bits
of a received ID according to the value in the corresponding slot of the C0IDR register upon acceptance
filtering operation. When the masking function is employed, it is possible to receive a certain range of IDs.
Figure 17.21 shows correspondence of the mask registers and slots, Figure 17.22 shows the acceptance
function.
Figure 17.21 Correspondence of Mask Registers to Slots
ID of the
received message
Figure 17.22 Acceptance Function
When using the acceptance function, note the following points.
(1) When one ID is defined in two slots, the one with a smaller number alone is valid.
(2) When it is configured that slots 14 and 15 receive all IDs with Basic CAN mode, slots 14 and 15
receive all IDs which are not stored into slots 0 to 13.
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0
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C0GMR register
C0LMAR register
C0LMBR register
ID stored in
the slot
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Slot #0
Slot #1
Slot #2
Slot #3
Slot #4
Slot #5
Slot #6
Slot #7
Slot #8
Slot #9
Slot #10
Slot #11
Slot #12
Slot #13
Slot #14
Slot #15
The value of the
mask register
17. CAN Module
Mask Bit Values
0: ID (to which the received message
corresponds) match is handled as
"Don't care"
1: ID (to which the received message
corresponds) match is checked
Acceptance Signal
Acceptance judge signal
0: The CAN module ignores the
current incoming message
(Not stored in any slot)
1: The CAN module stores the
current incoming message in
a slot of which ID matches
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