Specifications

Message Objects
10-12
Bits 3–0 DLC. Data Length Code
This value determines how many data bytes are used for transmission or re-
ception.
0000 0 bytes
0010 2 bytes
0100 4 bytes
0110 6 bytes
1000 8 bytes
10.3.2 Message Buffers
Message storage is implemented by RAM. The contents of the storage ele-
ments are used to perform the functions of acceptance filtering, transmission,
and interrupt handling.
The mailbox module provides six mailboxes, each consisting of 8 bytes of
data, 29 identifier bits, and several control bits. Mailboxes 0 and 1 are for re-
ception; mailboxes 2 and 3 are configurable as receive or transmit; and mail-
boxes 4 and 5 are transmit mailboxes. Mailboxes 0 and 1 share one accep-
tance mask, while mailboxes 2 and 3 share a different mask.
Note: Unused Message Mailboxes
Unused mailbox RAM may be used as normal memory. Because of this, you
must ensure that no CAN function uses the RAM area. This is usually done
by disabling the corresponding mailbox or by disabling the CAN function.
10.3.3 Write Access to Mailbox RAM
There are two different types of write accesses to the Mailbox RAM:
1) write access to the identifier of a mailbox
2) write access to the data or control field.
Note:
Write accesses to the identifier can only be accomplished when the mailbox
is disabled (MEn = 0 in MDER register).