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Altera_Forum
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14 years ago

Signal tap giving bizarre values

Hello i've used a lot of signal tap in my developer life however i am working in a project right now and it's behaving really weird.

I am using Quartus V11.0sp1, i've set some constant values at the input of a module and they are changing... how is that possible? A lot of registers that i am not changing the value in my code are swapping the value (says signaltap)

My acquisition clock is 100mhz and so is my system clock, i am running continuous capture of signal tap...

Is there any known issue with V11.0sp1 and signal tap?

4 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    14 years ago

    It may be a problem of JTAG signal quality. You can check if reloading the same acquisition gives constant data, then it can be expected correct.

  • Altera_Forum's avatar
    Altera_Forum
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    14 years ago

    Are you using a Altera/Terrasic USB blaster or another one? I have this problem when I'm using an EEBlaster under Linux. Switching to an Altera USB blaster and/or Windows fixes my problem.

  • Altera_Forum's avatar
    Altera_Forum
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    13 years ago

    Hello,

    I am having exactly the same problem reported by aprado, but I am using Signaltap of quartus v10.1sp1 on Windows.

    I've never experienced this before... and it is scaring me!

    I've got a signal stuck at '1'. If I put the trigger on a change of its value never happens. But if I trigger on some other signal that really moves, then I see the previous signal that changes!!

    I am using a USB Blaster cable.

    Please let me know if anyone has some hits because it is really frustrating.

    Bye
  • Altera_Forum's avatar
    Altera_Forum
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    13 years ago

    Hello All,

    I'm seeing a similar issue. I'm using Quartus 12.0 sp2. The signaltap gives crazy values for ~100 clks but then it corrects itself.

    For Instance, I have a decrementing counter.. it's counting down... then all of the sudden something happens.. then the counter goes to zero.. all the other signals get missed up too. After the crazy blip the counter resumes counting down.. it's value it resumes at is less than the value before the blip. It's weird because i know its happening but i can never trigger on it.... I can trigger of real transitions that make sense but i can never trigger on something in the crazy zone. It's almost like it didn't really happen and the fpga is running as normal but the signal tap memory gets corrupted for a short period of time.

    Another thing i've noticed is that the signal tap takes a long time of offload data... these is a lag whenever i push any button.

    This makes it very difficult to try to debug anything.. so any advice would help.