SAM7X256_14 Datasheet, PDF (486/662 Pages) ATMEL Corporation – ARM-based Flash MCU

It is also possible to configure a mailbox in Consumer Mode. In this mode, after each transfer request, a remote frame is
automatically sent. The first answer received is stored in the corresponding mailbox data registers.
Several mailboxes can be chained to receive a buffer. They must be configured with the same ID in Receive Mode,
except for the last one, which can be configured in Receive with Overwrite Mode. The last mailbox can be used to detect
a buffer overflow.
Mailbox Object Type
Receive
Receive with overwrite
Consumer
Description
The first message received is stored in mailbox data registers. Data remain available until the
next transfer request.
The last message received is stored in mailbox data register. The next message always
overwrites the previous one. The application has to check whether a new message has not
overwritten the current one while reading the data registers.
A remote frame is sent by the mailbox. The answer received is stored in mailbox data register.
This extends Receive mailbox features. Data remain available until the next transfer request.
36.6.2.3 Transmit Mailbox
When transmitting a message, the message length and data are written to the transmit mailbox with the correct identifier.
For each transmit mailbox, a priority is assigned. The controller automatically sends the message with the highest priority
first (set with the field PRIOR in CAN_MMRx register).
It is also possible to configure a mailbox in Producer Mode. In this mode, when a remote frame is received, the mailbox
data are sent automatically. By enabling this mode, a producer can be done using only one mailbox instead of two: one
to detect the remote frame and one to send the answer.
Mailbox Object Type
Transmit
Producer
Description
The message stored in the mailbox data registers will try to win the bus arbitration immediately
or later according to or not the Time Management Unit configuration (see Section 36.6.3).
The application is notified that the message has been sent or aborted.
The message prepared in the mailbox data registers will be sent after receiving the next remote
frame. This extends transmit mailbox features.
SAM7X Series [DATASHEET]
6120K–ATARM–11-Feb-14
486