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Observer phalpern
Observer
2,078 Views
Registered: ‎05-26-2011

Video PHY, HDMI, character and channel alignment

I've generated the Video PHY core, ver 2.0 from Vivado 2016.4.  This is configured for HDMI Rx, and No Tx.  We are not using the hdmi_rx core, just the Video PHY.  Our target deice is XCKU060.

1.  The HDMI specification provides certain 10-bit characters to be used to synchronize the bit stream.  And, the GTHE3 appears to provide synchronization using the Comma Alignment features.  But in the PHY product Guide (PG230) I don't see any indication if that is used.  In fact, I don't see anything indicating whether the output stream is character-aligned or not.  So, does the Video PHY guarantee proper character alignment by the time the received data is available on the AXI4S stream?

2.  Does the PHY Receiver provide channel bonding, so that all three output streams are aligned to each other?

Thanks very much.

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Xilinx Employee
Xilinx Employee
1,973 Views
Registered: ‎07-31-2012

Re: Video PHY, HDMI, character and channel alignment

Are you planning to use the video phy with your own version of the HDMI IP? The Video Phy has been specifically designed for using with Xilinx HDMI IP's and hence recommended to be used with this.

There are registers which check the alignment status. Yes, since it is serial transmission using GT's alignment should be done.

Yes, even channel bonding should be done, else the 3 channels would not be aligned and hence the data cannot be recovered. However I am not 100% sure. You can go into the generated files and check the GT configuration to validate.
Thanks,
Anirudh

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Observer phalpern
Observer
1,963 Views
Registered: ‎05-26-2011

Re: Video PHY, HDMI, character and channel alignment

Thanks for the input, Anirudh.

 

Yes, we will be using our own HDMI decoder modules.  Our needs are just a bit different than a typical receiver, and we'd prefer to avoid the large "black box" nature of the Xilinx HDMI receiver core.

You state that alignment and bonding "should be done", but do you know this to be the case?  I agree that it "should" be done.  But that doesn't mean it "is" done!  :)

 

So, again, the main question:  Is character alignment and channel bonding done by the PHY (using the GT resources, or any other means), or does the PHY assume those tasks will be handled by the HDMI receiver section?

 

I did start looking into the code.  As far as I can tell, neither function is being performed in the GTH.  However, since the PHY also interacts with a software driver (which we will use), it is conceivable that the driver configures these features through DRP-type controls.

 

Thx

Paul

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