Forum Discussion

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

multichannel FIR output timing error

When I use multichannel fir filter, the timing of output channels is not correct.

The output generated by 1 channel shifted. For example, First channel data filtered out to second channel, second channel data filerd out to third channel.

Why is it incorect? Please help me.

5 Replies

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

    what version and what parameters?

    can you just stick an impulse into channel 0 and grab a SignalTap with the input and output?
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    15 years ago

    Hi,pjw0112

    I have the same problem. Please give me some advice. Thanks!

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

    Did either of you find a solution to your problem?

    I have a two channel filter but have only been putting signals into channel 0. I have been debugging a DC block module. Eventually I decided there was a timing issue on the input (output of the FIR). With a bit of messing I found the signal appears on channel 1.

    Is this the same as what you are seeing?

    I have to make a few hardware modifications to my test boards before I can stuff a signal into channel 1.

    my dc block simulates ok. I use Altium Logic Analyser (which is the same as signal tap, i think).

    any advice?

    Quartus 9.2, 2 channel, decimating by 8, parrallel

    update- I have connected channel 0 and it seems that the output is swapped. That is, I is on channel 0 and Q is on channel 1, feeds the FIR. The output is Q channel 0 and I on channel 1.

    The actual filtering and data signals are fine.

    I have probably crossed my Is and Qs somewhere. I shall recheck the input to the FIR, but the output is definitly as above.
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    15 years ago

    I have checked and checked and the inputs to outputs are reversed

    I with SOP & Valid, Q with EOP & Valid go in

    Q with SOP & Valid & Channel 0, I with EOP & Valid & Channel 1 comes out

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

    I think I've had a similar issue with a multichannel CIC filter. 8 inputs between SOP and EOP and these appear in a jumbled (but in a constant) position at the outputs relative to the output EOP/SOP.

    My problem was the thing generating the input data.

    There were some spurious DV's on the input, the first signal to enter the filter was an EOP rather than an SOP and the third packet had one DV too many between the SOP and EOP.

    Bad design on my part:oops:. I fixed these and problem dissappeared. I suspect it was the extra DV between SOP/EOP.

    Check your inputs carefully.