Use the following steps whenever you scan a JTAG chain with Universal Scan to get up and running quickly:

1. Connect your download cable to the PC and hardware under test and apply power.

2. Bring up Universal Scan.  Add a port, select address and cable type - DON'T add devices yet.

3. Run the "DEVICE COUNT" Tool in the tools menu.  This will run a diagnostic on your JTAG chain
    and tell you if it is solid.  

    If it says "There are 3 devices in the chain" (and you really have 3 devices in the chain) then you are
    all set.  The chain is solid and stable.  Go to Step 4.

    If it says something like: "There appears to be 3 devices in the chain, but we only got the result
    79% of the time" then the JTAG chain is not stable and you need to figure out what the issue is 
    before proceeding.  This is usually caused by noise or signal coupling on the JTAG lines.

    If it says "There are no devices in the chain" then Universal Scan is unable to talk to the chain.
    Double check your connections, make sure TRST is high (if any), and make sure any special
    conditions required by the DUT to run Scan are met (Motorola and TI processors in particular - see
    FAQ page for details).  Contact us if you get stuck. techsupport@UniversalScan.com

    The great thing about the Device Count Tool is it requires nothing but a download cable. No BSDL
    files are needed!

4. Once DEVICE COUNT passes, add your devices to the screen and then run the VALIDATE BSDL Tool
    under the Tools menu.

    This tool will compare the BSDL files you selected with the hardware on the board to make sure
    you got the right ones.

     If this says all PASS, then you are ready to start scanning your design.

     If this indicates an issue, look at the details tab for clues.

     Again, if you get stuck, contact us. techsupport@UniversalScan.com

5. Once you get past DEVICE COUNT and VALIDATE BSDL, you should be ready to scan and add Virtual 
    LEDs & Switches until your heart is content.
 

Check out Application Note 004 for some ideas on implementing JTAG in your design.