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 Gb/s. The NI-DRU runs at 2.5 Gb/s, which enables it to recover line rates that cannot be supported by the transceiver.
- 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.
TMDS Clock Frequency (MHz)
|Line Rate (Gb/s)||Line Rate CFG*||HDMI Standard||Notes|
TX: 1 or 2
RX: NI-DRU is used
|125 to 204.688||1.25 to 2.046||1||HDMI 1.4||CDR is used|
|204.688 to 297||2.046 to 2.97||2||HDMI 1.4||CDR is used|
|85 to 102.344||3.4 to 4.094||3||HDMI 2.0||CDR is used|
|102.344 to 148.5||4.094 to 5.94||4||HDMI 2.0||CDR is used|
The following table is for illustration only. For unlisted color formats, support might be possible if they are not restricted by the VCO frequency range.
|Resolution (Hz)||Bits Per Pixel|
|WXGA + 60||DRU||DRU||√||√|