Help Understanding TMDS - Dom Needs Your Help!

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Discussion Overview

The discussion focuses on understanding the TMDS (Transition Minimized Differential Signaling) datasheet for a SIL150A TMDS transmitter/encoder, particularly in relation to connecting RGB signals and clock inputs for a DVI setup. Participants explore the technical details of pin assignments and signal types, as well as the differences between analog and digital outputs.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • Dom expresses confusion about the pinout for the TMDS transmitter, specifically regarding the connection of RGB signals and clock inputs.
  • Some participants suggest that the inputs for the TMDS transmitter are parallel, requiring all 8 bits of each color to be delivered simultaneously.
  • There is a clarification that PIXS held LOW sets the 1-pixel clock input mode, contrary to Dom's initial understanding.
  • One participant notes that the TMDS transmitter outputs a digitally modulated signal, which results in an analog output.
  • Dom acknowledges the feedback and indicates a willingness to try the suggestions provided.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the correct interpretation of the TMDS datasheet, with some conflicting views on the nature of the outputs and the required input configurations.

Contextual Notes

There are unresolved assumptions regarding the specific configurations needed for the TMDS transmitter and the implications of using different types of outputs (analog vs. digital).

Severence
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Hi my names Dom, just joined the forum and look forward too getting to know you other members.

Hopefully I've posted this in the right section.

I'm struggling to understand a TMDS datasheet and was hoping someone with a bit more know-how could help me out (draw it in crayons for me) :D

I have a source device that outputs three 8bit serial RGB lines as well as clock, Hsync and Vsync. I've read through the datasheet for a SIL150A TMDS transmitter/encoder and the pinout is confusing me.

Untitled.jpg


If i understand it correctly (unlikely) my serial 8 bit red signal would go to DIE23 Pin 90, green to DIE15 pin 99, and blue to DIE7 Pin 9 and this would give me 1-pixel clock input mode? input clock, HYSNC & VYSNC all seem pretty self explanatory to hook up (although I'm probably wrong about that too)

If the above is correct? what are the outputs to the corresponding inputs... for a DVI setup for example, is it TX1+ etc?

Thanks in advance to anyone who can help out.
 

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Edit: above, seems as though the transmitter above can only output analog (i think) and not digital, hdmi, dvi which is what I'm after, but the same principles apply to other TMDS transmitters such as analog devices ADV7513
 
Severence said:
I'm struggling to understand a TMDS datasheet and was hoping someone with a bit more know-how could help me out (draw it in crayons for me) :D

I looked at the datasheet and it's pretty self-explanatory. :rolleyes:


Severence said:
If i understand it correctly (unlikely) my serial 8 bit red signal would go to DIE23 Pin 90, green to DIE15 pin 99, and blue to DIE7 Pin 9

No, the inputs are parallel. You have to deliver the entire 8 bits for each colour at the same time (so for red you place a 8 bit value at DIE16-23. Check the Input Pin Description section in the datasheet PDF (p.4).

Severence said:
this would give me 1-pixel clock input mode?

No, PIXS held LOW sets 1-pixel mode.

Severence said:
what are the outputs to the corresponding inputs... for a DVI setup for example, is it TX1+ etc?

I don't know much about TDMS but it looks like it uses 4 differential pairs - TX0+/-, TX1+/-, TX2+/- and TXC+/- for transmission.
 
Severence said:
seems as though the transmitter above can only output analog (i think) and not digital, hdmi, dvi

The output is a digitally modulated signal, so the result is analog. That's Digital Communications 101.
 
Last edited:
Thanks for your resposne, youve been a great help.

I'll have a bash at it and report back :)

cheers.
 

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