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Cheaptag — JTAG cable for CPLD-flashing

Design by Andy


This cable allows to flash Xilinx CPLDs such as the one on PassMe. It connects to the printer port and is supported by the freely available Xilinx iMPACT flashing software.

Parts needed

  • DB-25 male connector or printer cable
  • 4.7k resistor (1/4 Watt)
  • Two 1.5V batteries or some other 3.3V power source
  • 2x6 header (optional)



Solder wires as indicated in the diagram. Don't make the cable too long (30cm or less is fine). For the connection to Passme you can either solder the wires directly to the PassMe and then desolder after programming or you can use a connector. If you decide to go with the connector, I recommend getting a standard 2x6 header and bending the pins so that there is good contact when PassMe is inserted between the two rows of the header.

You can use two 1.5V batteries in series if you don't have a better 3.3V power source.



Download the free (after registration) Xilinx ISE WebPACK which includes iMPACT from here

Connect JTAG cable and the power source and run iMPACT (the tool which will flash the PassMe)

Select "Configure Devices" and press "Next"

Select "Boundary-Scan Mode" and press "Next"

Select "Automatically connect to cable and identify Boundary-Scan chain" and press "Next"

It should find the CPLD and show it on the screen. Assign configuration file by clicking "OK" and then selecting the JED file to be flashed.

Right-click the CPLD and select "Program..."

Make sure "Verify" is selected and click "OK". Now the CPLD will be programmed.

Hopefully programming will be successful. If not, check power source and lines. Try programming on different computer.

© 2010 Alexei Karpenko (natrium42)