TMDS Mode LCPLL Use - 1.0 English

Using the LCPLL for the HDMI receiver includes certain restrictions. The TX does not have these restrictions because the GT driver uses oversampling techniques to work around the limitations of the LCPLL. The HDMI RX limitations for the LCPLL are described in this section.

The LCPLL voltage controlled oscillator (VCO) must run in the range of 8.0 GHz to 16.375 GHz. The VCO frequency is dependent on the TMDS clock frequency. The LCPLL can apply a limited set of multipliers to the TMDS clock frequency. The GT driver measures the TMDS clock frequency and attempts to find a suitable line rate configuration to complete the reconfiguration process. If the detected TMDS Clock frequency is outside normal operating mode, the HDMI GT Controller switches to NI-DRU Mode for RX or Oversampling mode for TX.

NI-DRU mode

When the GT driver detects that the TMDS clock frequency is less than 125 MHz, it enables the NI-DRU to receive bit rates that are less than 1.25 Gbps. The NI-DRU runs at 2.5 Gbps, which enables it to recover line rates that the transceiver cannot support.

Oversample Mode

When the GT driver detects that the TMDS clock frequency is less than 125 MHz, it puts the TX in oversampling mode and applies a multiplier of 2, 3, or 5 to the TMDS clock to put the TX above the minimum line rate.

The following table is for illustration only. For unlisted color formats, support might be possible if the VCO frequency range does not restrict them.