This is a small experimental project to validate the functionality of Xilinx FPGA Configuration JTAG USER4 register, which applied by Xilinx BSCANE2 [1] module in Verilog source code. This method should be applied to all offical Xilinx JTAG cable product, but currently I only test on Digilent USB-JTAG port, which is officialy supported by Xilinx on Vivado platform.

With Xilinx BSCANE2 module, it's much easiler to transfer binary data between PC and FPGA via Xilinx official JTAG cable. For example, when build digital laboratory environment on Digilent Arty board, use USB-JTAG for configuring FPGA bitstream and transfer test data to FPGA module, save the USB-UART to receive readable string from FPGA module in terminal application on PC.

Currently, BSCANE2 module has been parameterized as 32-bit register for JTAG DR-SHIFT state, as JDATA_WIDTH parameter in jtag_test module. But it's not only support byte (8-bit) aligend register operation, as learn-rv32i-arty project, which interfacing JTAG USER4 register by 41-bit width for RISC-V Debug Module Interface (DMI) data-structure.

I assume the reader for this project are familiar with Xilinx Vivado project mode, which based on Xilinx Vivado 2017.4 WebPack edition, and FPGA applied on Digilent Arty board.

Adhere, this README focus on how to use Xilinx Software Command-line Tools (XSCT) to perform Xilinx JTAG USER4 register read/write operations. If you want to know the development walkthrough, please reference the blog post: [Xilinx JTAG Toolchain 101] (TBD).

1. Clone project respository

git clone https://github.com/watz0n/arty_xjtag.git

2. Open arty_jtag.xpr by Xilinx Vivado 2017.4 in Project Mode
3. Push Generate bitstream, then select Yes in No Implementation Results Availble dialog
4. Attach PC and Arty by USB cable
5. Select Open Hardware Manager in Bitstream Generation Complete, then push Yes
6. Select Open Target, Auto Connect
7. Push Program Device, use Bitstream File right most ... button to select file arty_jtag.runs/impl_1/jtag_test.bit, then push Program button
8. Push >> (immediately sampling data) button in hw_ila_1, jtag_data should be 00000000(hex)

1. Open Xilinx Software Command Line 2017.4 under Xilinx Design Tools
2. Load jtag_reorder.tcl, for example, the project directory is d:\project\arty_xjtag

# Notice the path layer difference between Windows(\) and Linux(/)
# XSCT use Linux(/) form
xsct$ source d:/project/arty_xjtag/tcl/jtag_reorder.tcl

3. Setup Xilinx JTAG sequence as jseq object

xsct% connect
xsct% jtag targets
  1  Digilent Arty 210319755023A
     2  xc7a35t (idcode 0362d093 irlen 6 fpga)
        3  bscan-switch (idcode 04900101 irlen 1 fpga)
           4  unknown (idcode 04900220 irlen 1 fpga)
xsct% jtag targets 2
xsct% set jseq [jtag sequence]

4. Send data by JTAG sequence in XSCT [3]

# Select JTAG Register USER4 [2]
xsct% $jseq irshift -state IDLE -hex 6 23
xsct% $jseq drshift -state IDLE -hex 32 [jtag_reorder 12345678]
xsct% $jseq run
xsct% $jseq clear

5. Back to Vivado Hardware Manager hw_ila_1, push >>, jtag_data should be 12345678
6. Read data by JTAG sequence in XSCT [3]

# Select JTAG Register USER4 [2]
xsct% $jseq irshift -state IDLE -hex 6 23
xsct% $jseq drshift -state IDLE -tdi 0 -capture 32
xsct% set result [jtag_reorder [$jseq run]]
12345678
xsct% $jseq clear
xsct% puts $result
12345678

After previous step 3, setup JTAG sequence as jseq

# Select JTAG Register IDCODE [2]
xsct% $jseq irshift -state IDLE -hex 6 09
xsct% $jseq drshift -state IDLE -tdi 0 -capture 32
xsct% set result [jtag_reorder [$jseq run]]
0362d093
xsct% $jseq clear
xsct% puts $result
0362d093

Result as reference [2], Artix 7A35T X362D093

1. Xilinx UG429 : 7Series FPGAs Migration Methodology Guide

BSCAN_VIRTEX6 -> BSCANE2
JTAG_SIM_VIRTEX6 -> JTAG_SIME2
SIM_CONFIG_V6 -> SIM_CONFIGE2

2. Xilinx UG470 : FPGA Configuration Guide

3. Xilinx UG1208 : XSCT Reference Guide

• learn-rv32i-arty project, port unpipelined RV32I simulation core learn-rv32i-asap in Digilent Arty board Artix 7A35T FPGA.

If you have any questions, corrections, or feedbacks, please email to me or open an issus.

• E-Mail: [email protected]
• Blog: https://blog.watz0n.tech
• Backup: https://watz0n.github.io