Controller Area Network XL
CAN XL (Controller Area Network eXtended Length) is an extension of the traditional CAN (Controller Area Network) protocol used in automotive and industrial applications for communication between electronic control units (ECUs). The CAN XL protocol was developed by CiA CAN in Automation and is designed to meet the increasing demand for higher bandwidth and longer data frames in modern vehicles and industrial applications.
CAN XL is the third CAN data link layer protocol.[1]. It is backwards compatible to CAN FD[2]. It was originally developed to meet the bandwidth gap between CAN FD (Flexible Data rate) with 5-8 Mbit/s and 100 Mbit/s Ethernet for the automotive industry[3]. CAN XL expands the opportunities of the low-cost, robust CAN world.[4] The CAN and CAN FD protocol are standardized in the ISO11898-1:2015[5]. The CAN XL standard was submitted[6] to a working group in the ISO and they are updating the ISO 11898-1[7] with CAN XL[8]
CAN XL increases the payload data length of a CAN frame from a maximum of 8 bytes in traditional CAN, from a maximum of 64 bytes in CAN FD (Flexible Data rate) to up to 2048 bytes, enabling faster transmission of large data packets. It also offers improved error detection and correction capabilities and supports the use of more flexible data rates up to 20 Mbit/s.
The CAN XL protocol is backward compatible with existing CAN FD[2] networks, allowing for a smooth transition to the new protocol without requiring a complete overhaul of the existing infrastructure. The protocol is expected to be widely adopted in the automotive industry, where it can support emerging applications such as advanced driver assistance systems (ADAS) and autonomous driving. Other application example for the CAN XL is as a backbone in automotive E/E-Architecture.[9]
Comparison of CAN, CAN FD and CAN XL[edit]
| Property | Classical CAN | CAN FD | CAN XL |
| Data Field | [0 ... 8 byte] | [0 ... 64 byte] | [1 ... 2048 byte] |
| Identifier | 11 bit & 29 bit | 11 bit & 29 bit | 11 bit |
| Bus Access | CSMA/CR (Arbitration) | CSMA/CR (Arbitration) | CSMA/CR (Arbitration) |
| Acceptance Field | – | – | 32 bit (Message ID) |
| VCAN ID | – | – | 8 bit |
| SDU Type | – | – | 8 bit |
| Bit Stuffing | dynamic | dynamic
fixed in CRC |
dynamic (in arbitration field)
fixed (in data phase) |
| CRC | 15 bit | 17 or 21 bit | PCRC: 13 bit
FCRC: 32 bit (outperforms Flexray & Ethernet) |
| Error Signaling | ON | ON | Software Configurable: ON/OFF |
| Transceiver Mode Switching | Not supported | Not supported | Software Configurable: ON/OFF |
| Bit rate ratio: data/arb | – | Up to approx. 16. | Up to 40 (e.g. 500 kbit/s & 20 Mbit/s) |
| Arbitration phase bit rate
Data phase bit rate |
[0 ... 1 Mbit/s]
– |
[0 ... 1 Mbit/s]
[arb. phase bit rate ... 8 Mbit/s] |
[0 ... 1 Mbit/s]
[2x arb. phase bit rate ... 20 Mbit/s] |
New Functions in CAN XL versus CAN FD[edit]
CAN XL offers higher speed, up to 20Mbit/s and data payload, up to 2048 byte compared to CAN FD.
Increases safety with 2x CRC included in the CAN XL protocol.[10]
For higher layers (on Layer 2)[11] the following features in the CAN XL were added:
- SDT (Service Data Type): SDU[12] (Service Data Unit) Type (8 bit)
- Indicates the type of the protocol embedded in the data field
- In the CAN in Automation CiA611-1 (CAN XL higher layer functions - Part 1: Definition of service data unit types) already defines an SDT value for Ethernet Tunneling[13]
- VCID: Virtual CAN Network ID (8 bit)
- Allows to separate the CAN network/bus into up to 256 virtual networks
- Comparable to VLAN ID in Ethernet
- AF: Acceptance Field (32 bit)
- Depending on SDT (Service Data Type) it can contain
- Message ID or
- Source/Destination address
- Allows to support both:
- Content based addressing
- Node based addressing
- Depending on SDT (Service Data Type) it can contain
MAC frame format of the CAN XL[edit]
MAC frame format of CAN XL[14]: See CiA610-1[15] for the exact frame format.
| Arbitration Field | Control Field | Data Field | CRC Field | ACK Field | EOF Field | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Priority ID | XL | ADS | SDT | SEC | DLC | SBC | PCRC | VCID | AF | Data Bytes | FCRC | FCP | DAS | ACK | EOF | |
| Arbitration Phase | Data Phase | Arbitration Phase | ||||||||||||||
- Priority ID: 11-bit ID for bus arbitration, purpose: bus access priority
- XL : Placeholder in this graphic for several Bits: e.g. Frame Format Switch → FD to XL Format
- ADS: Arbitration Data Sequence → Bit Rate Switching from Arbitration to Data Phase, several bits
- SDT: SDU (Service Data Type) Type (8 bit) → indicates the type of the protocol embedded in the data field (comparable to EtherType in Ethernet)
- SEC: SEC (1 bit) signals, if further Layer 2 functions added headers to the data field (e.g. Security, Fragmentation)
- DLC: Data Length Code (11 bit)
- SBC: Stuff Bit Count → count of dynamic stuff bits in the arbitration field, safeguards against specific error types
- PCRC: Preface CRC (13 bit) → Safeguards the bits up to PCRC
- VCID: Virtual CAN Network ID (8 bit) → allows to separate the CAN Bus into virtual buses (comparable to VLAN ID in Ethernet)
- AF: Acceptance Field (32 bit) → Field for the Addressing, the interpretation of this field depends on SDT
- Data: 1 to 2048 bytes user data
- FCRC: Frame CRC (32 bit) → Safeguards the whole frame, i.e. the bits up to the FCRC
- FCP: Format Check Pattern → Receiver checks if he is aligned to transmitted bit stream
- DAS: Data Arbitration Sequence → Bit Rate Switching from Data to Arbitration Phase
- ACK: Positive Acknowledgement, same as in CAN FD
- EOF: End of Frame, same as in CAN FD
Transceiver - Physical Layer for CAN XL[edit]
The CAN XL protocol can operate with all existing physical Transceiver[16] for CAN and CAN FD and the newer CAN SIC (Signal Improvement Capability) Transceiver.[17]
For CAN XL also a new type of Transceiver was defined, the CAN XL SIC Transceiver. This transceiver is defined in the released spec CiA 610-3.[18]
The CAN XL SIC Transceiver with a data bit rate ≥ 8Mbit/s works with a push-pull topology and the Error Signalling is not available in this mode. This mode is called FAST mode.
The CAN XL SIC has two different modes:
- SIC (Signal Improvement Capability) mode
- dominant/recessive (like a CAN SIC transceiver)
- data rate up to 8Mbit/s
- FAST mode
- TX node: push/pull (0/1)
- RX node: adjust threshold
- data rate higher than 8Mbit/s up to 20Mbit/s
Security[edit]
CAN XL offers better security possibilities than CAN FD, by implementing the new "CANsec" standard to be sent before frame buffers and ensure message authenticity.[19]
Microcontroller compatibility[edit]
Infineon Technologies announced the TC4x series of controllers with CAN XL[20]
NXP Semiconductors offers the NXP S32 Platform
ST Microelectronics offers the Stellar Integration MCUs
References[edit]
- ↑ "Controller Area Network Extra Long (CAN XL)". CAN in Automation (CiA). Retrieved February 3, 2022.
- ↑ 2.0 2.1 Zeltwanger, Holger (2022). Zonal Network Architecture and CAN Networks. Wiesbaden: Springer Vieweg. pp. 501–508. ISBN 978-3-658-37008-4. Search this book on
- ↑ "Future of CAN networking in VW's passenger cars". CiA CAN in Automation. Retrieved 2022-05-02.
- ↑ Bäro, Stephan; König, Andreas (December 2021). "03 December 2021". ATZ Electron Worldwide. 16 (12): 46–51. doi:10.1007/s38314-021-0713-9 – via Springer Link. Unknown parameter
|s2cid=ignored (help) - ↑ "Road vehicles — Controller area network (CAN) — Part 1: Data link layer and physical signalling". ISO. Retrieved 2022-08-25.
- ↑ "CAN XL submitted for ISO standardization". CAN in Automation. 11 February 2022. Retrieved 2022-08-25.
- ↑ 14:00-17:00. "ISO 11898-1:2015". ISO. Retrieved 2022-01-28.
- ↑ "CAN XL and higher-layer protocols". can-newsletter.org.
- ↑ "CAN XL als Backbone im Fahrzeug". all-electronics. Retrieved 2022-10-02.
- ↑ "Evaluation of the CAN XL error detection capabilities". CAN in Automation. 31 March 2021. Retrieved 2022-08-23.
- ↑ "CAN XL and higher-layer protocols". can-newsletter.org. Retrieved 2022-01-28.
- ↑ Rausch, Mathias (2022). Kommunikationssysteme im Automobil: LIN, CAN, CAN FD, CAN XL, FlexRay, Automotive Ethernet (in German) (1st ed.). Carl Hanser Verlag GmbH & Co. KG. p. 229. ISBN 9783446470354.CS1 maint: Unrecognized language (link) Search this book on
- ↑ "The Art of Networking (Series 5): CAN XL and 10BASE-T1S – Gateway Performance of Two New Actors in the Networking Arena | Renesas". www.renesas.com. Retrieved 2023-09-21.
- ↑ "CAN in Automation (CiA): Controller Area Network Extra Long (CAN XL)". www.can-cia.org. Retrieved 2022-01-28.
- ↑ "CiA 610-1". CiA CAN in Automation.
- ↑ Hell, Magnus (September 2021). "The Physical Layer in the CAN XL world". ResearchGate. Retrieved 2022-10-17.
- ↑ "Physical layer options". CAN in Automation (CiA). Retrieved February 3, 2022.
- ↑ "CAN XL Medium Attachment Unit". embeddedcomputing.
- ↑ Hammerschmidt, Christoph (2022-06-22). "Security IP hardens CAN XL against cyber attacks". eeNews Europe. Retrieved 2023-09-21.
- ↑ AG, Infineon Technologies. "Erstes Silizium verfügbar: Infineon baut führende Position als Automotive-Halbleiterlieferant mit der nächsten AURIX™-Generation TC4x weiter aus - Infineon Technologies". www.infineon.com. Retrieved 2022-01-28.
External links[edit]
- CAN XL THE NEXT STEP IN CAN EVOLUTION
- https://www.can-cia.org/can-knowledge/can/can-xl/
- https://cdn.vector.com/cms/content/events/2019/VTT19/presentations/VTT19_24102019_CAN_XL_Room_for_Improvement.pdf
- https://www.renesas.com/in/en/blogs/art-networking-series-4-can-xl-and-10base-t1s-dataline-performance-two-new-actors-networking-arena
- Webinar
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