CAN -FD

-

 



What is CAN -FD

  • CAN-FD is a communication protocol based on CAN> 
  • CAN-FD is an improvement over CAN. 
  • Modern CAN controllers support both CAN and CAN-FD frames 
Note: CAN-FD is not a substitute for CAN protocol. A Single automotive network can have both CAN frames and CAN-FD frames. 
so CAN-FD protocol must be compatible with CAN protocol. 

Advantages of CAN-FD over CAN 

  • Data:  CAN -FD frame can carry up to 64 bytes of data whereas CAN carries 8 Bytes
  • Speed: CAN-FD  frame maximum speed up to 5Mbps  whereas CAN frame up to 1Mbps. 

Note: CAN-FD has dual speed (bit rate ). Data and CRC fields can be transmitted at a higher speed. The remaining fields of the frame will be transmitted with a lower speed, the same as the CAN speed. 


The orange colour field will transmit at a lower speed. and the Blue colour field will transmitted at a higher speed.



CAN and CAN FD use the same SOF –a single “dominant” bit

  • Little difference between CAN and CAN FD arbitration fields
  • Both share the same addressing for Standard and Extended formats
  • CAN FD removes the RTR bit and maintains an always dominant RRS bit

  • CAN and CAN FD share the following bits:
  •          - IDE , res and DLC bits
  •  
  • CAN FD adds the following bits to the control field:
  •      - FDF (FD Frame)
  •      - BRS (Bit rate switch)
  •      - ESI (Error state indicate)


FDF (FD Frame) :
             - Determines CAN FD (recessive)
            -  in classical CAN this bit is not present 
BRS (Bit rate switch) :
            - Clock rate switches when BRS is recessive
ESI –Error State Indicator (error active/pasive) 




Control Field: DLC

  • 4 bits are used for both formats (CAN and CAN-FD)
  • For DLC ≥ 8, CAN FD uses the follow


Data Field :

  • 0-8 bytes in CAN
  • 0-8, 12, 16, 20, 24, 32, 48, or

CRC Field: Stuff Count

  • How many Stuff bits are there in the bit stream are provided in the Frame after Data field. 

CRC Field: CRC Sequence



  • The size of CRC differs based on CAN/CAN FD and the length of DLC
  • 15 bits for CAN
  • 17 bits for CAN FD where DLC  ≤  16 bytes
  • 21 bits for CAN FD where DLC  >  16 bytes

CAN-FD : Dual Speed and Higher Payload




















Comments

Post a Comment

Popular posts from this blog

Overview of ISO/SAE 21434 Standard

-
Image
ISO/SAE 21434, jointly published by the International Standardization Organization (ISO) and the Society of Automotive Engineers (SAE), serves as a comprehensive cybersecurity framework for electronic systems within road vehicles. Developed to bolster cybersecurity across the entire lifecycle of automotive products, this standard outlines essential vocabulary, objectives, requirements, and guidelines. Purpose and Scope: The primary objective of ISO/SAE 21434 is to enhance cybersecurity measures for vehicles throughout their lifecycle. By providing a standardized framework, this standard facilitates the establishment of cybersecurity policies, risk management practices, and a cybersecurity-oriented culture within organizations operating in the automotive industry. Three Pillars: ISO/SAE 21434 is structured around three main pillars: Cyber Security Governance:   Establishing policies, processes, and cultural norms to govern cybersecurity activities within organizations. Risk Man...
Read more

Cryptography and Encryption Basics - I

-
Image
Cryptography and Encryption Basics I What is encryption Encryption is the process of encoding a message or information in such a way that only authorized parties can access it and those who are not authorized can't.  Converts information from plain text into encrypted ciphertext. But how...? Encryption used algorithm! An algorithm is a procedure that the encryption process follows. The specific algorithm is called the ciper or code. there are many types so encryption algorithms. The encryption's goal and level of security determine the most effective solution. Triple DES, RSA and Blowfish are some examples of encryption algorithms or Ciphers. What is Decryption? Decryption is the process of taking encoded or encrypted text or other data and converting it back into text that you or the computer can read and understand.  converts information from encrypted ciphertext into plain text  Basic Example  Private key vs Public Key Private Key (symmetric key): This means that ...
Read more

ECU LIST

-
Image
 1. BCM (Body Control Module)    - Function: The BCM is responsible for controlling various electronic systems within the vehicle's body. This includes functions like interior lighting, power windows, door locks, windshield wipers, and other comfort and convenience features.    - Importance: It acts as a central hub for various sensors and inputs, ensuring that the vehicle’s body-related electronics operate smoothly.  2. Gateway ECU    - Function: The Gateway ECU acts as a communication hub between different networked ECUs in the vehicle. It ensures that data is correctly routed between systems like powertrain, infotainment, and body control.    - Importance: Vital for ensuring seamless communication between various subsystems in modern vehicles.  3. ETM (Electric Traction Motor)    - Function: Manages the electric traction motor, which provides propulsion in electric or hybrid vehicles. It controls the motor's speed, torq...
Read more