Hello guys, welcome back to our blog. In this article, I will discuss the XCP protocol or universal measurement and calibration protocol, its working, architecture, and commands.

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XCP (Universal Measurement And Calibration Protocol)

In modern automotive and embedded systems, efficient communication protocols are essential for real-time measurement, calibration, and flashing of electronic control units (ECUs). One such widely used protocol is XCP (Universal Measurement and Calibration Protocol). Developed by the Association for Standardization of Automation and Measuring Systems (ASAM), XCP is an evolution of CCP (CAN Calibration Protocol) and provides high flexibility and efficiency across various transport layers.

This guide covers all aspects of XCP, including its architecture, working principles, transport layers, use cases, benefits, and comparison with other protocols.

01. What is XCP?

XCP (Universal Measurement and Calibration Protocol) is a standardized protocol for measuring and calibrating ECUs in real time. It enables fast, efficient, and flexible data acquisition, calibration, and flashing functionalities via different transport layers such as CAN, Ethernet, FlexRay, and SPI.

1.1 History and Development

Developed by ASAM (Association for Standardization of Automation and Measuring Systems)
Successor of CCP (CAN Calibration Protocol)
Designed to be transport-independent, unlike CCP, which was limited to CAN

1.2 Key Features

Transport-independent: Works over CAN, Ethernet, FlexRay, and other transport layers
High performance: Supports high-speed data acquisition and large data volumes
Standardized structure: Compatible with various tools and software solutions
Flexibility: Supports dynamic memory allocation and real-time calibration
Security: Offers encryption and authentication mechanisms

1.3 Transport Layers

XCP can be implemented on various transport layers:

Transport Layer	Protocol Used
XCP on CAN	ISO 11898
XCP on Ethernet	TCP/IP
XCP on FlexRay	FlexRay Protocol
XCP on USB	USB Protocol

02. XCP Architecture and Working Principle

XCP follows a master-slave architecture where the master (calibration tool) communicates with one or multiple slaves (ECUs).

2.1 XCP Master-Slave Architecture

Master: Typically a PC-based calibration and measurement tool (e.g., ETAS INCA, Vector CANape, dSPACE ControlDesk)
Slave: ECU running XCP software stack, responding to commands from the master

2.2 XCP Communication Model

XCP communication consists of:

Commands: Sent by the master to the slave to request specific actions
Responses: Sent by the slave to confirm the execution of commands
DAQ (Data Acquisition) Lists: Used for real-time data measurement
STIM (Stimulation) Lists: Used to send data to the ECU for control purposes

2.3 XCP Message Structure

XCP messages contain the following:

PID (Packet Identifier): Identifies the type of XCP message being sent.

0xFF – Command message
0xFE – Response message
0xFD – Error message
0xFC – Event message

Command/Response Data: Each command is followed by data fields that define the requested operation. The response from the ECU contains acknowledgment, requested data, or error information.

Error Handling Information: If an error occurs, the ECU returns an error response (0xFD) with a specific error code.

Example error response:

0xFD 0x21  // ERR_ACCESS_DENIED

Example XCP Command and Response

a. Initialization – Connecting to ECU

Command: Connect Request (Master → Slave)

0xFF 0x00 0x00 0x00 0x00 0x00 0x00 0x00  // Connect command

Response: Connect Confirmation (Slave → Master)

0xFE 0x00 0x00 0x00 0x00 0x00 0x00 0x00  // Successful connection response

b. Read Memory – Retrieve Calibration Parameter

Command: Read Memory (Master → Slave)

0xFF 0x00 0x10 0x00 0x00 0x04 0x00 0x00  // Read memory command (4 bytes from address 0x1000)

Response: Memory Content (Slave → Master)

0xFE 0x00 0x12 0x34 0x56 0x78  // Data from requested memory location

c. Write Memory – Modify Calibration Parameter

Command: Set Calibration Value (Master → Slave)

0xFF 0x00 0x20 0x00 0x05 0xAA 0xBB 0xCC  // Write 3 bytes (0xAA, 0xBB, 0xCC) to address 0x2000

Response: Acknowledge (Slave → Master)

0xFE 0x00 0x00  // Acknowledge successful calibration

d. Start Data Acquisition (DAQ)

Command: SET_DAQ_LIST_MODE

0xFF 0xE0 0x01 0x00 0x00 0x01

Response: Acknowledge

0xFE 0x00

03. Transport Layers Supported by XCP

One of the major advantages of XCP over CCP is its support for multiple transport layers. The following transport layers are commonly used:

3.1 XCP on CAN (XCP-on-CAN)

Used in traditional automotive applications
Limited by CAN’s bandwidth (1 Mbps)
Suitable for low-speed applications

3.2 XCP on Ethernet (XCP-on-Ethernet)

High-speed alternative to CAN, supporting 1 Gbps+ bandwidth
Preferred for complex ECUs and high-speed logging
Enables cloud-based diagnostics and calibration

3.3 XCP on FlexRay (XCP-on-FlexRay)

Used in safety-critical applications
Higher bandwidth than CAN, with deterministic communication

3.4 XCP on SPI (XCP-on-SPI)

Used in embedded systems and chip-level communications
Offers low latency and high-speed data exchange

04. XCP Protocol Features

4.1 Measurement & Calibration

Online and Offline Calibration: Enables parameter tuning without affecting ECU operation
Real-time Measurement: Supports high-frequency data logging

4.2 Flash Programming

XCP allows for firmware updates and the reprogramming of ECUs
Faster than traditional UDS-based flashing

4.3 Security Mechanisms

Seed & Key Authentication
Secure XCP (S-XCP) with encryption

05. Setting Up XCP in Vector CANoe

To set up XCP communication in Vector CANoe, follow these steps:

Step 1: Configure the CANoe Environment

Open Vector CANoe.
Create a new configuration or open an existing one.
Add the XCP Transport Layer under the Network Hardware Configuration.

Step 2: Add the XCP Protocol

Navigate to Database and select Add Protocol.
Choose XCP on CAN (or another transport layer like XCP on Ethernet).

Step 3: Load the A2L File

Go to System Variables and click Import A2L.
Load the A2L (ASAP2) file that contains ECU calibration information.

Step 4: Establish Communication

Start the CANoe measurement.
In the Simulation Setup, select XCP Master and connect to the ECU.

Conclusion

XCP is a powerful protocol for ECU measurement and calibration, widely used in the automotive industry. With tools like Vector CANoe, engineers can efficiently interface with ECUs, perform calibration, and validate automotive systems.

By following this guide, you can set up XCP communication, execute commands, and troubleshoot ECU interactions effectively.

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This was about “XCP (Universal Measurement And Calibration Protocol) – A Complete Guide“. Thank you for reading.

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Chetan Shidling

Automotive | Technical Blogger | Engineer | Content Creator

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