at91sam9263 ATMEL Corporation, at91sam9263 Datasheet - Page 674

• Manufacturer Part Number: at91sam9263
• Description: At91 Arm Thumb Microcontrollers
• Manufacturer: ATMEL Corporation

37.7.3
37.7.3.1
Figure 37-11. Receive Mailbox
Note:
674
Simple Receive Mailbox
Receive with Overwrite Mailbox
(CAN_MSRx)
(CAN_MSRx)
(CAN_MCRx)
CAN_MDHx)
(CAN_MDLx
In the case of ARM architecture, CAN_MSRx, CAN_MDLx, CAN_MDHx can be read using an optimized ldm assembler
instruction.
AT91SAM9263 Preliminary
CAN BUS
CAN Controller Message Handling
MRDY
Receive Handling
MTCR
MMI
Reading CAN_MDHx & CAN_MDLx
Two modes are available to configure a mailbox to receive messages. In Receive Mode, the
first message received is stored in the mailbox data register. In Receive with Overwrite Mode,
the last message received is stored in the mailbox.
A mailbox is in Receive Mode once the MOT field in the CAN_MMRx register has been config-
ured. Message ID and Message Acceptance Mask must be set before the Receive Mode is
enabled.
After Receive Mode is enabled, the MRDY flag in the CAN_MSR register is automatically
cleared until the first message is received. When the first message has been accepted by the
mailbox, the MRDY flag is set. An interrupt is pending for the mailbox while the MRDY flag is set.
This interrupt can be masked depending on the mailbox flag in the CAN_IMR global register.
Message data are stored in the mailbox data register until the software application notifies that
data processing has ended. This is done by asking for a new transfer command, setting the
MTCR flag in the CAN_MCRx register. This automatically clears the MRDY signal.
The MMI flag in the CAN_MSRx register notifies the software that a message has been lost by
the mailbox. This flag is set when messages are received while MRDY is set in the CAN_MSRx
register. This flag is cleared by reading the CAN_MSRs register. A receive mailbox prevents
from overwriting the first message by new ones while MRDY flag is set in the CAN_MSRx regis-
ter. See
Message 1
Figure
37-11.
Reading CAN_MSRx
Message 2 lost
Message 1
Writing CAN_MCRx
Message 3
Message 3
Message ID = CAN_MIDx
6249D–ATARM–20-Dec-07