1. CAN ( Controller Area Network )
RTLAB
김병철
08/03/20

2. 개요
CAN 이란?
AT91SAM7 의 CAN

3. CAN 이란?
BOSCH 에서 자동차용 전자제어 장치들 간의 실시 간 통신을 위해 개발 ( Ex : ABS, 엔진관리, 변속관 리 )
CSMA/CD+AMP (carrier-sense multiple-access protocol with collision detection and arbitration on message priority)
Simple 2-wire differential bus
Bit rates up to 1Mbit/s
3종류의 CAN 버전
Four Frame Types
Five Error Types
Fault Confinement

4. CAN 계층 구조

5. CAN 노드 구조

6. CAN 적용 사례
6->7 : 2개의 Bus로 어떻게 데이터 통신을 하는가?

7. Bus Condition 뒤로 The Inverted Logic of a CAN Bus CANH와 CANL의 차가
0.5V 보다 작으면 Recessive ‘1’
0.9V 보다 크면 Dominant ‘0’
두개의 Bus값을 검사하여 다르면 “0” 같으면 “1” 뒤로

8. Bus Condition
Bus에 대해 Dominant가 Recessive보다 우선순위가 높다!

9. CSMA/CD with AMP
CSMA/CD with AMP (arbitration on message priority)

10. CAN Bit Coding & Bit Stuffing
NRZ Bit Coding
Stuff Bits are inserted after 5 consecutive bits of the same level for synchronization

11. CAN Bit Timing Configuration뒤로

12. CAN Frame Formats CAN Versions
Standard CAN ( V2.0A ) : 11-Bit Identifier
Extended CAN ( V2.0B ) : 29-Bit Identifier
Identifier = Priority

13. CAN Frame Formats
1Mbps의 속도로 data가 전송된다면 Standard의 경우 130us, Extended의 경우 154us의 시간이 소요된다.
    1       start bit
+  11     Identifier bit
+  1       SRR bit
+  1       IDE bit
+  18     Identifier bit
+  1       RTR bits
+  6       Control bits
+  64     Data bits
+  15     CRC bits
+  23     (maximum) Stuff bits
+  1       CRC delimiter
+  1       ACK slot
+  1       ACK delimiter
+  7       EOF bits
+  3       IFS bits
=  154    bits
    1       start bit
+  11     Identifier bit
+  1       RTR bits
+  6       Control bits
+  64     Data bits
+  15     CRC bits
+  19     (maximum) Stuff bits
+  1       CRC delimiter
+  1       ACK slot
+  1       ACK delimiter
+  7       EOF bits
+  3       IFS bits
=  130    bits
Standard
Extended

14. Relation between BitRate and Bus Length

15. CAN Frame Formats Four Frame Types Data Frame (RTR=0)
Remote Frame (RTR=1 and no data field)
Error Frame (after violation frame format)
Overload Frame (Not really used)

16. Error Detection Error Types CRC error Bit-stuffing error Bit error
Form Error
Acknowledgment error

17. Fault Confinement ERRA bit is set in the CAN_SR Register
ERRP bit is set in the CAN_SR Register

18. AT91SAM7의 CAN CAN 2.0A and CAN 2.0B Bit rates up to 1Mbit/s
8 Mailboxes
Also called channels or buffers
The CPU reads or writes data via the CAN controller mailboxes
Each mailbox has an ID
Several mailboxes can be configured with the same ID
Each can be Receive or Transmit one
16-bit Time Stamp

19. CAN Block Diagram

20. Mailbox Receive Mailbox Transmit Mailbox
Mailbox with the lowest number is serviced first
Mailbox Object Type
Receive
Receive with overwrite
Consumer
Transmit Mailbox
Mailbox with the highest priority is serviced first
Same priority -> mailbox with lowest number first
Transmit
Producer

21. Message Acceptance Procedure
MIDx : Mailbox ID register
MAMx : Acceptance Mask register

22. Message Acceptance Procedure

23. Receive Mailbox

24. Receive with Overwrite Mailbox

25. Chaining Receive Mailboxes
All mailboxes are configured with same ID
The mailbox with the largest number is configured in receive with overwrite mode (others are configured in receive mode)

26. Transmitting Messages

27. Producer/Consumer model

28. Producer / Consumer Handling

29. CAN Controller Timing Modes
Timestamping Modes
The value of the internal timer is captured at each Start Of Frame or each End Of Frame

30. CAN Controller Timing Modes
Time Triggered Mode

31. CAN Controller Timing Modes
Time Triggered Mode