Download - 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
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Background & TargetCAN XL – Next Step in CAN Evolution
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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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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
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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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
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
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
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