JTAG Test Access Port (TAP)

Project maintainers


Name: jtag
Created: Sep 25, 2001
Updated: Jan 25, 2018
SVN Updated: Mar 10, 2009
SVN: Browse
Latest version: download (might take a bit to start...)
Statistics: View
Bugs: 1 reported / 0 solved
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Other project properties

Development status:Stable
Additional info:
WishBone compliant: No
WishBone version: n/a


This implementation of the Test Access Port (TAP) is fully IEEE 1149.1 compliant. It includes a TAP controller, a 4-bit instruction register and three test data registers: idcode register, bypass register and boundary scan register. Boundary scan register is connected to eight pins (2 inputs, 2 outputs, 2 tristatable outputs and 2 bidirectional pins). Besides the Verilog code, a BSDL file is also provided. The number of pins can be easily increased by following the instructions. The design had been tested with the JTAG Technologies testing equipment (The TAP controller was implemented in Xilinx 95144XL). The design will be expanded in the future to support additional instruction and debug capabilities.


- New release of the TAP controller. Sections used for debugging were put in a separate project (dbg_interface) - New release of the specification document. - A description of a Boundary Scan Implementation(57KB) is avaliable in Adobe PDF format (see Downloads). - JTAG debug interface for the OR1k processor is finished. - Verilog and BSDL files can be accessed via cvsweb.

Next step

- nothing at the moment