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Visitor trax.xavier
Visitor
1,729 Views
Registered: ‎01-03-2018

TRD 2017.2 why is the Video Phy controller needed?

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Hello,

 

I'm playing around with the Reference design TRD 2017.2

 

As far as I see the video data for HDMI in and out first go through the "Video Phy controller" before being connected input/output blocks, i fail to understand the reason behind that, I read the pg230-vid-phy-controller.pdf but its still not clear to me why not connecting the input/output ports directly to the respective blocks?

 

Any explanations would be greatly appreciated

 

Cheers

Trax

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Xilinx Employee
Xilinx Employee
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Registered: ‎08-02-2007

Re: TRD 2017.2 why is the Video Phy controller needed?

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@trax.xavier Video PHY receives/transmits TMDS data and forwarding clock, it plays two roles here : 

1. At data side,

- Receiver side, the received TMDS data is serial data, which HDMI RX System only accept the link data. Video PHY converts it to 40bits parallel link data, which can be driven to HDMI RX IP. It has GT underhood, which needs to do some alignment and reset sequence, Video PHY also send status signal to tell HDMI that link data is ready.

- Transmit side is the other way around, but idea is similar

 

2. At clock side

TMDS clock is forwarding clock. Before you receive it, you have no idea what clock frequency will be received, the video clock frequency needs to be adjusted dynamically, depending on the color information.

 

Video PHY plays as a clock manager, receiver side, it detects the TMDS clock frequency, and decide which refclk is supported to GT, and provide video clock with correct frequency to HDMI IP.

 

At transmit side, it calculates the clock frequency, makes sure it's correct for associated resolution of video data that you intend to transmit.

6 Replies
Scholar austin
Scholar
1,610 Views
Registered: ‎02-27-2008

Re: TRD 2017.2 why is the Video Phy controller needed?

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t,

 

For versatility in design.  If your application can be simplified, then simplify it.  The Base TRD is useful for the SDx design flow where as little as possible is done in Vivado, and most of the design proceeds at a higher level (C/C++).

 

Please do not multiple post -- we will find your post and move it to the correct board if we feel you have put your question in the wrong place.

 

 

Austin Lesea
Principal Engineer
Xilinx San Jose
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Visitor trax.xavier
Visitor
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Registered: ‎01-03-2018

Re: TRD 2017.2 why is the Video Phy controller needed?

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For versatility, great.

but what exactly does it do?

Is this the point where SDx hooks in with the filters?

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Scholar austin
Scholar
1,592 Views
Registered: ‎02-27-2008

Re: TRD 2017.2 why is the Video Phy controller needed?

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More mundane,

 

Look at figure after 3.

 

http://www.wiki.xilinx.com/reVISION+Getting+Started+Guide+2017.4

 

You will see the 'stuff' placed in the PL to stitch everything together.


In the DP as output, all of that is built into the PL DP, so none of that gets put in PL.


It all has to play with v4l2, so presumably what gets added is to be sure everything plays nicely, software with hardware.

 

 

Austin Lesea
Principal Engineer
Xilinx San Jose
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Moderator
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Registered: ‎11-09-2015

Re: TRD 2017.2 why is the Video Phy controller needed?

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Hi @trax.xavier,

 

The Video PHY controls the GTs. It is the physical interface for the HDMI. So you need it to have the data outputed from the design.

 

Regards,


Florent
Product Application Engineer - Xilinx Technical Support EMEA
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Xilinx Employee
Xilinx Employee
2,272 Views
Registered: ‎08-02-2007

Re: TRD 2017.2 why is the Video Phy controller needed?

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@trax.xavier Video PHY receives/transmits TMDS data and forwarding clock, it plays two roles here : 

1. At data side,

- Receiver side, the received TMDS data is serial data, which HDMI RX System only accept the link data. Video PHY converts it to 40bits parallel link data, which can be driven to HDMI RX IP. It has GT underhood, which needs to do some alignment and reset sequence, Video PHY also send status signal to tell HDMI that link data is ready.

- Transmit side is the other way around, but idea is similar

 

2. At clock side

TMDS clock is forwarding clock. Before you receive it, you have no idea what clock frequency will be received, the video clock frequency needs to be adjusted dynamically, depending on the color information.

 

Video PHY plays as a clock manager, receiver side, it detects the TMDS clock frequency, and decide which refclk is supported to GT, and provide video clock with correct frequency to HDMI IP.

 

At transmit side, it calculates the clock frequency, makes sure it's correct for associated resolution of video data that you intend to transmit.

Visitor trax.xavier
Visitor
1,518 Views
Registered: ‎01-03-2018

Re: TRD 2017.2 why is the Video Phy controller needed?

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Awesome now I understand that part, thank you very much.

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