![background image](http://html1.mh-extra.com/html/texas-instruments/tms320x281-series/tms320x281-series_reference-manual_1095203036.webp)
2.10 Global Acceptance Mask Register (CANGAM)
Global Acceptance Mask Register (CANGAM)
www.ti.com
The global-acceptance mask is used by the eCAN in SCC mode. The global-acceptance mask is used for
the mailboxes 6 to 15 if the AME bit (MSGID.30) of the corresponding mailbox is set. A received message
is only stored in the first mailbox with a matching identifier.
The global-acceptance mask is used for the mailboxes 6 to 15 of the SCC.
Figure 2-10. Global Acceptance Mask Register (CANGAM)
31
30
29
28
16
AMI
Reserved
GAM[28:16]
RWI-0
R-0
RWI-0
15
0
GAM[28:16]
RWI-0
LEGEND: RWI = Read at any time, write during initialization mode only; -
n
= value after reset
Table 2-10. Global Acceptance Mask Register (CANGAM) Field Descriptions
Bit
Field
Value
Description
31
AMI
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 global acceptance mask register are used for
the filter. In case of a standard frame, only the first eleven bits (bit 28 to 18) of the identifier and the
global acceptance mask are used.
The IDE bit of the receive mailbox is a "don't care" and is overwritten by the IDE bit of the
transmitted message. The filtering criterion must be satisfied in order to receive a message. The
number of bits to be compared is a function of the value of the IDE bit of the transmitted message.
0
The identifier extension bit stored in the mailbox determines which messages shall be received.
The IDE bit of the receive mailbox determines the number of bits to be compared. Filtering is not
applicable. The MSGIDs must match bit-for-bit in order to receive a message.
30:29
Reserved
Reads are undefined and writes have no effect.
28:0
GAM 28:0
Global-acceptance mask. These bits allow any identifier bits of an incoming message to be
masked. Accept a 0 or a 1 (don't care) for the corresponding bit of the received identifier. Received
identifier bit value must match the corresponding identifier bit of the MSGID register.
eCAN Registers
36
SPRU074F – May 2002 – Revised January 2009