BSDL Files

Boundary Scan Description Language (BSDL) is a subset of VHDL that is used to describe how JTAG (IEEE 1149.1) is implemented in a particular device. For a device to be JTAG compliant, it must have an associated BSDL file.

These files are often available for download from manufacturers’ websites, free of charge (see below).

JTAG systems such as XJTAG use the information contained in a BSDL file to work out how to access a device in the JTAG chain.

BSDL files contain the following elements:

  • Entity Description: Statements naming the device or a section of its functionality.
  • Generic Parameter: A value such as a package type. The value may come from outside the current entity.
  • Port Description: Describes the nature of the pins on the device (input, output, bidirectional, linkage).
  • Use Statements: References external definitions (such as IEEE 1149.1).
  • Pin Mapping(s): Maps logical signals in the device to physical pins.
  • Scan Port Identification: Defines the pins used on the device to access the JTAG capabilities (TDI, TDO, etc – the Test Access Port).
  • Instruction Register Description: The signals used for accessing JTAG device modes.
  • Register Access Description: Which register is placed between TDI and TDO for each JTAG instruction.
  • Boundary Register Description: List of the boundary scan cells and their functionality.

The boundary scan cells in the Boundary Register Description are typically of types defined in the JTAG specifications; however it is possible for manufacturers to implement variations on the specified behaviour, and to create and provide their own non-standard cell types to define the behaviour of their devices.


Download BSDL files for your JTAG components

When the link doesn’t point to a list of files, please search for “BSDL”.


More BSDL files can be downloaded from the following community maintained website, but please be aware that the files may not be up to date: BSDL Files Library for JTAG.
(please note that this website is not connected to XJTAG and XJTAG is not responsible for their content).

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