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Altera_Forum's avatar
Altera_Forum
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14 years ago

Altera transceiver bits swapped

Hi all.

I'm working on a simple transceiver loopback test using a stratixIV GX development kit.

I instantiated a simple ALTGX function in basic (PMA direct) mode, and i attached the altera loopback connector to the HSMC board.

The reset sequence was done according to the reference documentation .

The transceiver is fed by a simple counter, but on the receiver side i see the counter with the bits misaligned (eg tx: ABCDEF rx: EFABCD).

Is this a known issue?What can I do to debug the design?

I can provide as much info as you need, even the whole design.

Thanks in advance

Marco

2 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    14 years ago

    this isnt a bug, you need to bitslip the data until it is aligned. generally there is a training sequence that is either spec'ed by the protocol, or is user specific.

  • Altera_Forum's avatar
    Altera_Forum
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    14 years ago

    Thanks a lot dwesterg,

    So for a "raw" transmission i need to implement myself a synch word and a FSM to realign the received data, right?

    But if i use a protocol (eg basic x4) i see in the signaltap anlyzer that the bits keep swapping.

    let's say the synch word is "0101111100", is it sent automatically or do i need to inject it periodically in the data?

    Thanks again!

    Marco

    (EDIT)

    the answer was yes, i need to inject the synch word and use an optional port to tell the transceiver when to realign.

    tnx