SAM3X8C Atmel Corporation, SAM3X8C Datasheet - Page 1231

• Manufacturer Part Number: SAM3X8C
• Manufacturer: Atmel Corporation

Figure 40-19. Mailbox Timestamp
40.8.4.2
Figure 40-20. Time Triggered Principle
11057A–ATARM–17-Feb-12
11057A–ATARM–17-Feb-12
MTIMESTAMP
MTIMESTAMP
TIMESTAMP
(CAN_TSTP)
(CAN_MSRx)
(CAN_MSRy)
Synchronization by a Reference Message
Transmitting within a Time Window
(CAN_MR)
CAN BUS
CAN_TIM
TEOF
Reference
Message
Time Triggered Mode
In Time Triggered Mode, basic cycles can be split into several time windows. A basic cycle starts
with a reference message. Each time a window is defined from the reference message, a trans-
mit operation should occur within a pre-defined time window. A mailbox must not win the
arbitration in a previous time window, and it must not be retried if the arbitration is lost in the time
window.
Time Trigger Mode is enabled by setting the TTM field in the CAN_MR register. In Time Trig-
gered Mode, as in Timestamp Mode, the CAN_TIMESTP field captures the values of the internal
counter, but the MTIMESTAMP fields in the CAN_MSRx registers are not active and are read at
0.
In Time Triggered Mode, the internal timer counter is automatically reset when a new message
is received in the last mailbox. This reset occurs after the reception of the End Of Frame on the
rising edge of the MRDY signal in the CAN_MSRx register. This allows synchronization of the
internal timer counter with the reception of a reference message and the start a new time
window.
A time mark is defined for each mailbox. It is defined in the 16-bit MTIMEMARK field of the
CAN_MMRx register. At each internal timer clock cycle, the value of the CAN_TIM is compared
Timestamp 1
Timestamp 1
Message 1
Time Cycle
Time Windows for Messages
Start of Frame
End of Frame
Global Time
Message 2
Reference
Message
Timestamp 2
Timestamp 2
SAM3X/A
SAM3X/A
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