Atmel Evaluation Kit AT91SAM9X25-EK AT91SAM9X25-EK データシート
製品コード
AT91SAM9X25-EK
903
SAM9X25 [DATASHEET]
11054E–ATARM–10-Mar-2014
enabled by setting TIMFRZ in the CAN_MR register. The CAN_TIM register is frozen to the FFFFh value. A clear
condition described above restarts the timer. A timer overflow (TOVF) interrupt is triggered.
condition described above restarts the timer. A timer overflow (TOVF) interrupt is triggered.
To monitor the CAN bus activity, the CAN_TIM register is copied to the CAN _TIMESTP register after each start of frame
or end of frame and a TSTP interrupt is triggered. If TEOF bit in the CAN_MR register is set, the value is captured at each
End Of Frame, else it is captured at each Start Of Frame. Depending on the corresponding mask in the CAN_IMR
register, an interrupt is generated while TSTP is set in the CAN_SR. TSTP bit is cleared by reading the CAN_SR register.
or end of frame and a TSTP interrupt is triggered. If TEOF bit in the CAN_MR register is set, the value is captured at each
End Of Frame, else it is captured at each Start Of Frame. Depending on the corresponding mask in the CAN_IMR
register, an interrupt is generated while TSTP is set in the CAN_SR. TSTP bit is cleared by reading the CAN_SR register.
The time management unit can operate in one of the two following modes:
Timestamping mode: The value of the internal timer is captured at each Start Of Frame or each End Of Frame
Time Triggered mode: A mailbox transfer operation is triggered when the internal timer reaches the mailbox trigger
Timestamping Mode is enabled by clearing TTM field in the CAN_MR register. Time Triggered Mode is enabled by
setting TTM field in the CAN_MR register.
setting TTM field in the CAN_MR register.
41.7.4 CAN 2.0 Standard Features
41.7.4.1 CAN Bit Timing Configuration
All controllers on a CAN bus must have the same bit rate and bit length. At different clock frequencies of the individual
controllers, the bit rate has to be adjusted by the time segments.
controllers, the bit rate has to be adjusted by the time segments.
The CAN protocol specification partitions the nominal bit time into four different segments:
Figure 41-4. Partition of the CAN Bit Time
TIME QUANTUM
The TIME QUANTUM (TQ) is a fixed unit of time derived from the MCK period. The total number of TIME QUANTA in a
bit time is programmable from 8 to 25.
bit time is programmable from 8 to 25.
SYNC SEG: SYNChronization Segment.
This part of the bit time is used to synchronize the various nodes on the bus. An edge is expected to lie within this
segment. It is 1 TQ long.
segment. It is 1 TQ long.
PROP SEG: PROPagation Segment.
This part of the bit time is used to compensate for the physical delay times within the network. It is twice the sum of the
signal’s propagation time on the bus line, the input comparator delay, and the output driver delay. It is programmable to
be 1,2,..., 8 TQ long.
signal’s propagation time on the bus line, the input comparator delay, and the output driver delay. It is programmable to
be 1,2,..., 8 TQ long.
This parameter is defined in the PROPAG field of the
.
PHASE SEG1, PHASE SEG2: PHASE Segment 1 and 2.
The Phase-Buffer-Segments are used to compensate for edge phase errors. These segments can be lengthened
(PHASE SEG1) or shortened (PHASE SEG2) by resynchronization.
(PHASE SEG1) or shortened (PHASE SEG2) by resynchronization.
Phase Segment 1 is programmable to be 1,2,..., 8 TQ long.
Phase Segment 2 length has to be at least as long as the Information Processing Time (IPT) and may not be more than
the length of Phase Segment 1.
the length of Phase Segment 1.
These parameters are defined in the PHASE1 and PHASE2 fields of the
.
INFORMATION PROCESSING TIME:
SYNC_SEG
PROP_SEG
PHASE_SEG1
PHASE_SEG2
NOMINAL BIT TIME
Sample Point