I'm working on an HDMI ASIC and the HDMI spec is very clear on everything except for the way that the +, -, and shield wires are used to transmit a given signal. The TDMS channels and the clock are all split into +, -, and shield. What do I need to do to get a correct single digital signal from those bundles of wires?

  • 4
    \$\begingroup\$ I do believe that is covered in the specification document. \$\endgroup\$
    – dext0rb
    Mar 29, 2014 at 15:12
  • \$\begingroup\$ Really high speed signals. The 3 channels are already very high speed, putting them on one is perhaps faster than you can make 'external circuits' for. \$\endgroup\$
    – kenny
    Mar 29, 2014 at 15:17

2 Answers 2


The cable and signalling technique you describe is for balanced differential data transmission. It's unlike a single output and ground that would feed via coaxial cable.

To receive a transmission you use a differential receiver. To transmit you use a differential line driver. This applies to both data and clock signals.

This technique emits less EM radiation and consequently is less susceptible to EM interference. It also relies on a balanced resistive terminator to impedance match to the cable's characteristic impedance.


You need LVDS (low-voltage differential signaling) receivers on your ASIC, one for each of the +/- pairs.

You should be able to find this in the ASIC cell library you're working with.


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