can xl – the next step in can evolution

CAN XL –THE NEXT STEP IN CAN EVOLUTION

FEBRUARY 2021

Current status of the CAN XL standardization @ CiA

AE/EIY4 | 2021-02-25

© Robert Bosch GmbH 2021. All rights reserved, also regarding any disposal, exploitation, reproduction, editing, distribution, as well as in the event of applications for industrial property rights.

Background & TargetCAN XL – Next Step in CAN Evolution

2

Inspired by VW’s demand for a higher bandwidth CAN solution,

officially presented by VW at the ISO/TC 22/SC 31/WG3 plenary

meeting in September 2018

Provide a superior 10Mbit/s CAN solution with respect to

► Price (Transceiver, Pins, Cabling, ...)

► Safety

► Security

► Quality of Service

Preserve CAN properties: Arbitration, robustness, long stubs, …Mbit/s

Co

st

2 10 100

100BASE-T1

10BASE-T1S

CAN FD

Bit-rate gapBackground

Target

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CAN XL – Next Step in CAN Evolution

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Arbitration Data Trailer

slow: ≤ 1Mbit/s | short: 11 bit ID fast: 1 to ≥12 Mbit/s | long: 1 to 2048 byte slow: ≤ 1Mbit/s

Bit rate ≥12 Mbit/s

Target net bit rate

10 Mbit/s with large payloads

Arbitration Phase

≤ 1 Mbit/s

Data Phase:

1 ... ≥12 Mbit/s – user configured, tradeoff

between bit rate & network topology

Priority ID / Message ID

Priority ID (bus access priority)

short (11 bit) enables high net bit rate

for short payloads

Message ID (identifies message)

long (32 bit) sent in “Acceptance Field”

during XL data phase

Data Field length

Range

1 .. 2048 byte (configurable with byte granularity)

Enables

transparent Ethernet frame tunneling, use

of TCP/IP, SOME/IP, and more

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Compatibility to CAN FDCAN XL – Next Step in CAN Evolution

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CAN FD: Has the res-Bit for future

protocol extensions

Compatibility of CAN FD and XL enables

Incremental upgrade path larger acceptance

E/E Architecture design freedom: “mixed FD/XL” or “XL only” networks

Mixed CAN FD/XL networks: 2 data bit rates on the same bus (CAN XL is limited to

SIC mode, no Transceiver mode switch allowed)

► right bandwidth for each bus node | bandwidth/price optimized endpoints

Mixed CAN FD / CAN XL network

CAN FD

CAN FD CAN FD CAN FD

CAN XLCAN XL

res-Bit = 0:

CAN FD node expects a CAN FD Frame

res-Bit = 1:

CAN FD node enters

Protocol Exception Mode – a kind of passive wait state

CAN FD node Ends

Protocol Exception Mode after the occurrence of 11

consecutive recessive bits

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MAC Frame FormatCAN XL – Next Step in CAN Evolution

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Arbitration Field Control Field Data Field CRC Field

Priority ID ADS DLCXL Data Bytes EOFFCPPCRC FCRCSDT SEC SBC VCID AF DAS ACK

ACK Field EOF Field

Arbitration-Phase Data-Phase Arbitration-Phase

FD Mode XL Mode FD Mode

Increased Robustness/Safety due to

Fixed Stuff Bits

simplicity & robustness against specific error

types (bit insertion/removal)

Preface CRC

safeguard DLC (Data Length Code)

Frame CRC

powerful, safeguards whole frame up to FCRC

01 02 03

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MAC Frame Format Details1

CAN XL – Next Step in CAN Evolution

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ACK Field EOF Field


FD Mode XL Mode FD Mode

Fixed Stuff Bits, 1 stuff bit after 10 data bits

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

SDT SDU 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, Segmentation)

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

Dyn. Stuff Bits No Stuff Bits

1 See CiA610-1 for the exact frame format

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New Functions on Layer 2CAN XL – Next Step in CAN Evolution

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ACK Field EOF Field

Layer 2 MAC frame format

SDT: SDU Type (8 bit)

Indicates the type of the protocol embedded

in the data field

Comparable to EtherType in Ethernet

CiA611-1 already defines an SDT value for

Ethernet Tunneling

Layer 2 Frame contains 3 new fields

VCID: Virtual CAN Network ID (8 bit)

Allows to separate the CAN network/bus into

virtual networks

Comparable to VLAN ID in Ethernet

AF: Acceptance Field (32 bit)

Depending on SDT it can contain

a) Message ID or

b) Source/Destination address or c) ...

Allows to support both:

1) Content based addressing

2) Node based addressing

01 02 03

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SDU Type (SDT)CAN XL – Next Step in CAN Evolution

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Content Based Addressing

Definition

Indicates the type of the protocol embedded in the data field – comparable to EtherType

CiA611-1 in the first version: will specify 4 SDU Types (specification of further values is planed)

... Data Field ...SDT ... AF

CAN Data0x01 Message ID

CAN Data0x02Dest. Address

Source Address

Legacy CAN Frame (FD or Classical)0x03 CAN Frame ID (11 / 29 bit ID)

Ethernet frame, without FCS0x04TruncatedDestination MAC Address

1 ... 2048 byte8 bit 32 bit

Node Addressing

IEEE 802.3 (Ethernet) Tunneling

IEEE 802.3 (Ethernet) Tunneling

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Transceiver Types usable with CAN XLCAN XL – Next Step in CAN Evolution

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TODAY

CAN FD Transceiver

2 Mbit/s in Data-Phase

(realistic with existing bus topologies)

CAN SIC Transceiver

(Signal Improvement, former “Ringing Suppression”)

5 Mbit/s in Data-Phase

TOMORROW

CAN FD Transceiver

currently under specification in SIG CAN XL

@ CiA ≥12 Mbit/s in Date-Phase

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0201

Properties of “CAN SIC XL” TransceiverCAN XL – Next Step in CAN Evolution

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Layer 2 (MAC)

SIC Mode

dominant/recessive (like a CAN SIC transceiver)

FAST Mode

TX node: push/pull (0/1)

The XL Protocol Controller signals the mode switch to the transceiver during ADS & DAS



ACK Field EOF Field


SIC Mode FAST Mode SIC Mode

Start signaling End signaling

RX node: adjust threshold

Layer 1 (Physical Layer)

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CAN Usability MatrixCAN XL – Next Step in CAN Evolution

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Protocol (Data Link Layer) CAN CAN FD CAN XL

Max. payload8

bytes

64

bytes

2048

bytes

Transceiver

(Physical Layer)CAN CAN FD CAN SIC CAN CAN FD CAN SIC

CAN SIC

XL FAST*

CAN SIC

XL FAST*

Max. bit rate in real

OEM applications

500

kbit/s

2

Mbit/s

5

Mbit/s

500

kbit/s

2

Mbit/s

5

Mbit/s

5

Mbit/s

≥10

Mbit/s

Error SignallingError

Flag

Error

Flag

Error

Flag

Error

Flag

Error

Flag

Error

Flag

not

available

not

available

Topology Dimension large normal large large normal largeextra

largelarge

* CAN SIC XL Transceiver operated in FAST Mode

Hint: CAN XL Transceiver operated in SLOW Mode = CAN SIC Transceiver

XL & FD compatible

mixed FD/XL network possible

XL and FD NOT compatible

pure CAN XL network

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CompatibilityCAN XL – Next Generation CAN

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Layer 1

(Physical Layer)

Layer 2

(Protocol)

CAN FD

Classic CAN

CAN XLError Signaling ON

CAN XLError Signaling OFF

SIC XL

use with mode switch

SIC XLuse without mode switch

SICFD

ClassicSame device

CAN FD ignores

CAN XL frames

Approx. max.

Bit Rate [Mbit/s]

Same device –

Mode configured

by software

0,5–2 5–8 5–8 12–15

ISLAND 1

Full compatibility of FD and XL up to 5-8 Mbit/s

ISLAND 2

CAN XL up to ≥12 Mbit/s

Compatible

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Comparison – Net Bit Rate over Payload SizeCAN XL – Next Step in CAN Evolution

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0,00

2,00

4,00

6,00

8,00

10,00

12,00

14,00

0 128 256 384 512 640 768 896 1024 1152 1280 1408 1536 1664 1792 1920 2048

Net

Bit

-Rat

e [M

bit

/s]

Payload Size [byte]

XL 15 Mbit/s XL 12,3 Mbit/s

XL 8 Mbit/s XL 5 Mbit/s

10BASE-T1S 10 Mbit/s FlexRay 10 Mbit/s

CAN XL Arbitration-Phase: 600 kbit/s

CAN XL has higher

net bit rate

Equal net bit rate

at 405 byte payload 15 Mbit/s

12 Mbit/s

8 Mbit/s

5 Mbit/s

XL Data-Phase

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DemonstratorCAN XL – Next Step in CAN Evolution

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Key Success FactorsCAN XL – Next Step in CAN Evolution

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Large payload size

allows tunneling of e.g. Ethernet traffic

(transparent for higher layer protocols)

All kind of payload types supported – including largest possible

Ethernet frame, IPv6, …

Extreme scalability

& wide range of bit rates configurable, any transceiver

(Classic, FD, SIC, SIC XL) usable

AUTOSAR support

Concept proposal since early 2020

– will be developed by end of 2021

Availability

CAN XL is technically finalized since Q4/2020,

CiA610-1 specification release planed Q1/2021

Bit rate ≥12 Mbit/s

just limited by selected PHY technology

CAN XL protocol targeted for high speed CAN XL transceivers (10 .. 12, .. ?

Mbit/s), but also works with CAN FD or CAN SIC transceivers with up to 8 Mbit/s

01

Incremental upgrade

& mixed networks (CAN FD & CAN XL)

Co-existence of “cheap” CAN FD and fast CAN XL nodes in same network

03

Supports complex network topologies

Flexible trade-off between speed and complex networks

(e.g. long stubs supported)

05

Price

expected to be cheaper than 10BASE-T1S

07

02

04

06

08

THANK YOU

can xl – the next step in can evolution

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