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209 Views
Registered: ‎06-17-2018

The behavior of the link up when the "link_reset_r2" is deleted in the tranceiver_wrapper.

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I'm using Aurora8B10B IP with the sideband mode.

As for the datasheet of the Aurora8B10B, the reset release of the TX is first, and second, the RX reset release.

But I think by the consideration of the hotplug, the case that the RX reset release first and TX reset release second would be OK.

So I deleted the “link_reset_r2” in the xxxx_AURORA_8B10B_GT_WRAPPER.v like this

rxfsm_soft_reset_r <= `DLY /*link_reset_r2 ||*/ GTRESET_IN || gtrxreset_pulse;

Because I thought that CPLL reset is not needed every time when the cc check, and this CPLL reset that happens so many times might cause “not link up” situation.

But this modification causes such a side-effect that when powered on, first TX and RX is not connected (sideband also not connected) and then connect TX and RX and sideband, no link up happens.

In this case RX buffer error happens even if TX and RX are connected and sideband connected.

If TX and RX are connected and sideband connected and power on, link up is OK and no buffer error.

And once link up Is OK, then next TX and RX not connected, sideband not connected, and again TX and RX are connected and sideband connected, link up OK.

So I wonder why this “/*link_reset_r2 ||*/” affects the link up behavior difference.

I want know the mechanism why these difference of the behavior happens.

 

1 Solution

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106 Views
Registered: ‎06-17-2018

Re: The behavior of the link up when the "link_reset_r2" is deleted in the tranceiver_wrapper.

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Thank you for reply.

Understood.

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2 Replies
Xilinx Employee
Xilinx Employee
145 Views
Registered: ‎03-30-2016

Re: The behavior of the link up when the "link_reset_r2" is deleted in the tranceiver_wrapper.

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Hello @katsuya.yamamoto 

1. We would not recommended any RTL modification unless it is necessary. This is un-supported usecase.
    I do not understand the necessity to remove "link_reset_r2".

2. Hot-plug logic purpose is to provide auto-reset to Aurora RX, in unexpected circumstances.
    For example when user reset Aurora TX,  we do not need to reset Aurora RX. 
    Since Hot-plug logic will do the job. It will reset whole Aurora RX (not only CPLL)

3. If you initialized RX first, without any valid serial input,
    GTX RX will not work properly, you will need to re-initialize GTX RX.
    But since you removed "link_reset_r2", no body do the initialization job for you.

  XF_AURORA_8B10B_modified_RTL.png

Hope this helps

 

107 Views
Registered: ‎06-17-2018

Re: The behavior of the link up when the "link_reset_r2" is deleted in the tranceiver_wrapper.

Jump to solution

Thank you for reply.

Understood.

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