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Altera_Forum's avatar
Altera_Forum
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15 years ago

can't access JTAG chain

Some time ago we purchased the Altera MAX II Development Kit, it works properly. Now we have modelled a board in a simplified form with a JTAG interface. When we transfer data we get this error message: "Can’t access JTAG chain ". These are my questions:

1. What are the basic requirements (hardware, schematic) you need to run the JTAG interface? Do I need SRAM for the circuit?

2. For the JTAG interface, we have the same schematic as for the Altera MAX Development Kit. During data transfer there is no signal at pin 3 JTAG (TDO). The supply voltage of 3.3 V at pins 4, 5, 9 is present. There is a voltage of 3.3V provided at pin 4 of the EC3953 crystal. Pin 2 is connected to GND. From pin 3, a frequency of 66 MHz is routed to the EPLD pin H5.

Maybe you have an idea what it could be why the JTAG is not responsive, despite the correct supply voltage and frequency. Thank you!</SPAN></SPAN>

6 Replies

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    15 years ago

    You don't need SRAM or a crystal clock for JTAG access. Your schematic looks fine to me. You're saying that V_CPLD_INT = 3V3. That should be ok. But I still can't find a source for it in your schematic. I can find a source for V_CPLD_IO but not for V_CPLD_INT.

    Ton
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    15 years ago

    Hello sinp0915, If you get "Can’t access JTAG chain" error message, most likely it means that the supply voltage is not present. Please check if you have the supply voltage. or if the contacts are good.