Meaning
A data format standard provides the structural description of a boundary scan-compliant integrated circuit to enable automated test generation. In practice, a BSDL file describes the test access port architecture and the boundary register cells of a specific silicon device. This file defines the physical pinout, the available instructions, and the mapping of internal shift registers to external connections.
Board-level test development relies on these files to verify electrical continuity without physical test probes.
Silicon Description
Syntax rules defined by IEEE 1149.1 govern the structure of the file, which is written as a subset of VHDL. When integrating a new microcontroller or system on chip, the designer obtains the BSDL file from the silicon vendor to define the boundary scan chain. The file contains statements that specify the pin mapping, the grouping of pins into differential pairs, and the electrical properties of the input and output buffers.
Verification of the file is done by running parser checks in the boundary scan development environment before generating the test program.
Instruction Mapping
Command registers are defined alongside their binary opcodes to allow the test software to control the internal state of the boundary cells. The BSDL compiler checks these opcodes against the supported IEEE standards to ensure compliance. Registers such as the bypass and boundary registers are explicitly declared with their respective bit lengths.
Designers use this information to calculate the scan cycle time and optimize the test throughput of the board.
Test Automation
Testing software reads these files to generate test vectors. These vectors run on automated test equipment.
