XCP

XCP or "Universal Measurement and Calibration Protocol" is a network protocol

originating from ASAM for connecting calibration systems to electronic control units,

ECUs. It enables read and write access to variables and memory contents of microcontroller

systems at runtime. Entire datasets can be acquired or stimulated synchronous to events

triggered by timers or operating conditions. In addition, XCP also supports programming of

flash memory.

ASAM states "The primary purpose of XCP is to adjust internal parameters and acquire the

current values of internal variables of an ECU. The first letter X in XCP expresses the fact

that the protocol is designed for a variety of bus systems."[1]

In 2003, the protocol was standardized as "ASAM MCD-1 XCP". XCP is a successor to

CAN Calibration Protocol (CCP) that was developed back in the mid-1990s. At that time,

CAN was the dominant networking system in the automobile industry. Over time, other bus

systems such as LIN, MOST and FlexRay emerged and made it necessary to extend the

protocol to other transport media. In addition, XCP supports synchronous and

asynchronous serial interfaces. With Ethernet or USB as the transport medium, XCP can

also serve as a standardized interface to analog measurement devices and to hardware

interface converters to RAM emulators, JTAG or other microcontroller debug interfaces.

Due to its broad range of use, a primary goal in the development of XCP was to achieve as

lean an implementation in the ECU as possible and high scalability of features and resource

utilization. XCP can even be implemented on 8-bit microcontrollers for CAN or SCI with

few resources, and it exploits the full potential of FlexRay or Ethernet on high-performance

platforms.

As a two-layer protocol, XCP consistently separates the protocol and transport layers from

one another and adheres to a Single-Master/Multi-Slave concept. XCP always uses the

same protocol layer independent of the transport layer. The X in its name stands for the variable and interchangeable transport layer. Currently, the following transport layers are

defined as standard by ASAM as of May 2010:[2]

XCP on CAN

XCP on CAN FD

XCP on SxI (SPI, SCI)

XCP on Ethernet (TCP/IP and UDP/IP)

XCP on USB

XCP on FlexRay

In addition to supporting other transport layers, the successor to the CCP protocol contains

many functional improvements such as:[3]

Better resource utilization in the ECU

Synchronous data stimulation

Support of start-up measurements

Optimized communication by block transfer commands

Plug & play configuration

More precise measurement data acquisition by measuring the time stamps in the

ECU (Slave)

XCP allows a client to access memory on the ECU using a format defined in a separate

A2L file. Because the A2L format file contains all the information to access the

information, the ECU code does not have to be recompiled to access different

measurements or calibrations