16.8.1 Local-Acceptance Masks (CANLAM)
The local-acceptance filtering allows the user to locally mask (don't care) any identifier bits of the incoming
message.
In the SCC, the local-acceptance-mask register LAM(0) is used for mailboxes 2 to 0. The local-acceptance-mask
register LAM(3) is used for mailboxes 5 to 3. For the mailboxes 6 to 15, the global-acceptance-mask (CANGAM)
register is used.
After a hardware or a software reset of the SCC module, CANGAM is reset to zero. After a reset of the eCAN,
the LAM registers are not modified.
In eCAN mode, each mailbox (0 to 31) has its own mask register, LAM(0) to LAM(31). An incoming message is
stored in the highest numbered mailbox with a matching identifier.
You can locally mask any identifier bits of the incoming message. A 1 value means "don't care" or accept either
a 0 or 1 for that bit position. A 0 value means that the incoming bit value must match the corresponding bit in the
message identifier.
If the local-acceptance mask identifier extension bit is set (LAMI = 1 => don't care) standard and extended
frames can be received. An extended frame uses all 29 bits of the identifier stored in the mailbox and all 29 bits
of local-acceptance mask register for the filter. For a standard frame only the first eleven bits (bit 28 to 18) of the
identifier and the local-acceptance mask are used.
If the local-acceptance mask identifier extension bit is reset (LAMI = 0), the identifier extension bit stored in the
mailbox determines the messages that are received.
Figure 16-8. Local-Acceptance-Mask Register (LAMn)
31
30
29
28
16
LAMI
Reserved
LAM
n
[28:16]
R/W-x
R/W-x
R/W-x
15
0
LAM
n
[15:0]
R/W-0
LEGEND: R/W = Read/Write; -
n
= value after reset (x:Undefined)
Table 16-7. Local-Acceptance-Mask Register (LAMn) Field Descriptions
Bit
Field
Value
Description
31
LAMI
Local-acceptance-mask identifier extension bit
1
Standard and extended frames can be received. In case of an extended frame, all 29 bits of the
identifier are stored in the mailbox and all 29 bits of the local-acceptance mask register are used for
the filter. In case of a standard frame, only the first eleven bits (bits 28 to 18) of the identifier and
the local-acceptance mask are used.
0
The identifier extension bit stored in the mailbox determines which messages shall be received.
30-29
Reserved
Reads are undefined and writes have no effect.
28-0
LAM[28:0]
These bits enable the masking of any identifier bit of an incoming message.
1
Accept a 0 or a 1 (don't care) for the corresponding bit of the received identifier.
0
Received identifier bit value must match the corresponding identifier bit of the MSGID register.
Controller Area Network (CAN)
1024
TMS320x2806x Microcontrollers
SPRUH18I – JANUARY 2011 – REVISED JUNE 2022
Copyright © 2022 Texas Instruments Incorporated
Содержание TMS320 2806 Series
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