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Altera_Forum's avatar
Altera_Forum
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10 years ago

Why is my software not producing the correct Avalon write?

I have my nios connected to an Avalon memory mapped bridge that will allow me to communicate with an external RTL component. All I am trying to do is read and write to a register in the RTL component, but no matter what I do I can not get writes to assert. My Avalon bridge is located at address 0x002_0000 - 0x002_0FFF. My code to write to the Avalon master is as follows: 

.text
.global main
.type main, @function
main:
  movi r10, 0x0020000
  movi r9, 0x00AA
  stwio r9, (r10)
end:
    br    end
.end

5 Replies

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

    Hi,

    Are you sure the address is correct ? The bridge changes the address, you need to add the bridge's address with the Avalon-MM slave component, to get the final address.

    Did you use signal tap to see if the bus transaction is correct ?
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    10 years ago

    Be careful with Avalon bridges. Check that you address is in DWords and not in symbols. Your address 0x20000 might be actually translated to 0x8000.

    Thanks,

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

    --- Quote Start ---

    Hi,

    Are you sure the address is correct ? The bridge changes the address, you need to add the bridge's address with the Avalon-MM slave component, to get the final address.

    Did you use signal tap to see if the bus transaction is correct ?

    --- Quote End ---

    I am currently running signal tap now and I am not seeing the write transaction I requested.

    What exactly do you mean that the bridge changes the address? I am looking at the address map in qsys and I see that the bridge is located at 0x0002_0000.
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    10 years ago

    --- Quote Start ---

    Be careful with Avalon bridges. Check that you address is in DWords and not in symbols. Your address 0x20000 might be actually translated to 0x8000.

    Thanks,

    Evgeni

    --- Quote End ---

    I did make sure to set the address to words.
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    10 years ago

    Did you connect your custom component within Qsys or the bridge is exported? Are you using Avalon-MM pipeline bridge?

    I hope that you did not export the bridge directly.

    Can you share you Qsys system design/address map?