KCU CAN / CAN FD communication architecture
KCU GEN1 provides 4 channels of CAN 2.0B; KCU GEN2 (Phase B / Micro) is upgraded to 4 channels of full CAN FD (up to 2 Mbit/s data phase), one of which supports CAN wake-up function.This article summarizes the hardware configuration, Wake-up behavior and KopherSAR software integration of the KCU series on CAN/CAN FD communication.
Summary
The CAN/CAN FD communication configuration of the KCU series is as follows: KCU GEN1 provides 4 channels of CAN 2.0B (3 channels for application and 1 channel for debugging).KCU GEN2 (Phase B) Upgraded to 4-way full CAN 2.0B / CAN FD.KCU GEN2 Micro is also a 4-channel full CAN FD (maximum data phase baud rate 2.0 Mbit/s). CAN A has wake-up capability and can wake up the transceiver and start the main controller through CAN messages.All channels are integrated through KopherSAR’s Can / CanIf / CanTp / PduR / COM modules, supporting Partial Networking and NM network management.
Technical Role
CAN (Controller Area Network) is the mainstream vehicle communication bus; CAN FD (Flexible Data Rate) is an enhanced version, providing:
- Larger data payload: up to 64 bytes per frame (8 bytes for CAN).
- Higher data phase baud rate: The data phase is increased to more than 2 Mbit/s, and the arbitration phase is maintained at 500 kbit/s.
- Improved CRC: Better immunity to interference.
The KCU platform provides different CAN configurations according to product positioning:
| Products | CAN Channels | CAN FD | Applications |
|---|---|---|---|
| KCU GEN1 | 4 (3 user + 1 debug) | No | Traditional vehicle communication application. |
| KCU GEN2 (Phase B) | 4 | Yes | Central VCU / vehicle main control node. |
| KCU GEN2 Micro | 4 | Yes | Subsystem Node/Smart Actuator ECU. |
CAN A (CAN GEN2 / Micro’s first channel) supports wake-up function: when the ECU enters a low-power state, the transceiver still monitors the bus and wakes up the main MCU when it encounters specific CAN packets.
Architecture
| Hierarchy | Role |
|---|---|
| Application Layer (SWC) | Send and receive Signals through RTE. |
| KopherSAR COM | Pdu Group / Signal Configuration and Callback. |
| PduR | Pdu routing (COM ↔ DCM ↔ NM ↔ CanTp). |
| CanTp | ISO-TP segmented transmission (for UDS, large messages). |
| CanIf | CAN Frame ↔ Pdu corresponding, Tx/Rx processing. |
| Can MCAL | Entity CAN Controller operation. |
| CAN Transceiver (TJA1145ATK/FD, etc.) | Physical layer transceiver, CAN Wakeup, Partial Networking. |
| Bus | Vehicle CAN/CAN FD bus. |
KopherSAR simultaneously integrates CanNm (CAN Network Management), CanSM (State Manager) and ComM (Communication Manager), and BswM switches the communication status between different Modes (NoCommunication / SilentCommunication / FullCommunication).
Key Capabilities
- GEN1: 4-channel CAN 2.0B, channel planning 3 user + 1 debug; supports standard 11-bit / extended 29-bit ID.
- GEN2 / Micro: 4-channel CAN 2.0B / CAN FD, maximum data phase 2.0 Mbit/s.
- CAN Wakeup: CAN A (GEN2 / Micro) supports PDU wakeup; can reduce static power consumption.
- Partial Networking: Low power monitoring of specific PDUs can be maintained on the main bus through transceiver support (TJA1145ATK/FD).
- ISO-TP: CanTp provides segmented transmission of large messages, and UDS services (such as 0x19, 0x34/0x36) are transmitted across frames through CanTp.
- NM: CanNm provides synchronized sleep/wake, vitality message coordination.
Engineering Inputs Required
| Input | Purpose |
|---|---|
| DBC / ARXML communication matrix | Configure Frame, Signal, Pdu, Routing. |
| Baud rate setting | Arbitration phase (normally 500 kbit/s) and data phase (CAN FD up to 2 Mbit/s). |
| Wakeup settings | Which Pdu triggers wake-up and hibernation entry conditions. |
| Partial Networking configuration | Which ECUs support PN, PN frame content. |
| Terminating resistors | The vehicle topology determines which nodes require 120 Ω terminating resistors. |
| ISO-TP requirements | Large message transmission (such as OTA, UDS Programming Session). |
| NM behavior | Wake-up synchronization, sleep coordination, Network Mode switching. |
How KopherBit Supports This
- BSW: KopherSAR provides complete Can / CanIf / CanTp / PduR / COM / CanNm / CanSM modules.
- Configuration: KopherConfig Import and generate ARXML, BSW configuration and code directly from DBC.
- Transceiver Integration: BCM / KCU platform supports transceivers with PN and wake-up such as TJA1145ATK/FD.
- Diagnostic Integration: CanTp + DCM fully supports UDS over CAN/CAN FD.
FAQ
KCU Is GEN1 upgradeable to CAN FD?
no.GEN1 master MPC5744P CAN Controller is CAN 2.0B specification and does not support CAN FD.If CAN FD is required, please select KCU GEN2 / KCU GEN2 Micro.
What is the difference between Wakeup and Partial Networking?
Wakeup is when the ECU is awakened from a low-power state by any CAN packet; Partial Networking is when the ECU is still powered on and only listens to a specific PDU and ignores other traffic to achieve low power consumption.Both can be used in combination.
Which CAN channels require 120 Ω termination resistors?
Depends on vehicle topology.Generally, there is a 120 Ω terminal resistor at both ends of the bus; KCU Whether a built-in terminal resistor is required depends on its position in the topology (endpoint vs. mid-section).
How much power does CAN A wake up actually consume?
The specific value depends on the CAN transceiver used and the KCU motherboard standby configuration.The TJA1145ATK/FD has typical single-digit mA quiescent current in PN/Wakeup mode.
Why does CAN FD data phase still need arbitration phase 500 kbit/s?
The arbitration phase must be compatible with all nodes, so it maintains 500 kbit/s (typical); CAN FD only switches to a higher baud rate during the data phase (data load transmission phase) and has no impact on non-CAN FD nodes.
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