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Chapter 16
FCAN Controller
User’s Manual U16702EE3V2UD00
16.9.3 Mask
function
It can be defined whether masking of the identifier that is set to a message buffer is linked with another
message buffer.
By using the mask function, the identifier of a message received from the CAN bus can be compared
with the identifier set to a message buffer in advance. Regardless of whether the masked ID is set to 0
or 1, the received message can be stored in the defined message buffer.
While the mask function is in effect, an identifier bit that is defined to be 1 by a mask in the received
message is not compared with the corresponding identifier bit in the message buffer.
However, this comparison is performed for any bit whose value is defined as 0 by the mask.
For example, let us assume that all messages that have a standard-format ID, in which bits ID27 to
ID25 are 0 and bits ID24 and ID22 are 1, are to be stored in message buffer 14. The procedure for this
example is shown below.
<1> Identifier to be stored in message buffer
Remark:
x = don’t care
<2> Identifier to be configured in message buffer 14 (example)
(Using CANn message ID registers L14 and H14 (CnMIDL14 and CnMIDH14))
ID with ID27 to ID25 cleared to 0 and ID24 and ID22 set to 1 is registered (initialized) to message
buffer 14.
Remark:
Message buffer 14 is set as a standard format identifier that is linked to mask 1 (MT[2:0] of
CnMCONF14 register are set to 010B).
ID28
ID27
ID26
ID25
ID24
ID23
ID22
ID21
ID20
ID19
ID18
x
0
0
0
1
x
1
x
x
x
x
ID28
ID27
ID26
ID25
ID24
ID23
ID22
ID21
ID20
ID19
ID18
x
0
0
0
1
x
1
x
x
x
x
ID17
ID16
ID15
ID14
ID13
ID12
ID11
ID10
ID9
ID8
ID7
x
x
x
x
x
x
x
x
x
x
x
ID6
ID5
ID4
ID3
ID2
ID1
ID0
x
x
x
x
x
x
x
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