a2L

A2L is a standardized, human- and machine-readable description format defined by ASAM (Association for Standardisation of Automation and Measuring Systems) for automotive electronic control units (ECUs). The A2L file, typically with a .a2l extension, describes measurement, calibration, and diagnostic data within an ECU, enabling external tools to access and interpret internal data without vendor-specific interfaces. It serves as a neutral contract between ECU software and calibration or test tools.

A2L files describe the software content of an ECU in a structured way. Key elements include modules, measurements (MEASUREMENT) and characteristics (CHARACTERISTIC), and axis descriptions (AXIS_DESCR) used for maps and multi-dimensional data. They also define data types, memory addresses or memory mapping (addresses in RAM or ROM), and byte order. Conversion rules, such as COMPU_METHOD and COMPU_TAB, specify how raw ECU values are converted to physical units. The format can also describe diagnostic data blocks, limits, and update rates.

Usage and workflow: during development and calibration, A2L files accompany the ECU software and are loaded into calibration tools, simulators, or diagnostic systems. The tools read the A2L to locate data, apply conversion formulas, and access memory via supported communication protocols (such as CCP, XCP, or UDS). This enables real-time measurement, calibration of maps and parameters, and data logging, while remaining compatible across different hardware and vendor implementations.

A2L is part of the ASAM MCD-2 MC standard and is widely adopted in the automotive industry. It provides a vendor-neutral description that supports interoperability among calibration systems, test rigs, and ECU software, facilitating data access, lineage, and reproducibility in development and testing processes.