SNLS543 August 2018 DS90UH949A-Q1
The DS90UH949A-Q1 automatically detects the capabilities of downstream links and can resolve whether a single device, dual-capable device, or multiple single link devices are connected.
In addition to the downstream device capabilities, the DS90UH949A-Q1 will be able to detect the HDMI pixel clock frequency to select the proper operating mode.
If the DS90UH949A-Q1 detects two independent devices, it will operate in Replicate mode, sending the single channel video on both connections. If the device detects a device on the secondary link, but not the first, it can send the video only on the second link.
Auto-detection can be disabled to allow forced modes of operation using the Dual Link Control Register (DUAL_CTL1).
The frequency detection circuit may cause change in Single / Dual mode during a temperature ramp. When the ambient temperature around the DS90UH949A-Q1 changes by more than 40°C and when PCLK is between 60 MHz and 78 MHz, the auto-detect feature can switch device configuration from Single-lane to Dual-lane mode (or vice-versa) even though the input PCLK has not changed. This causes a configuration change in Deserializer resulting in a momentary loss of lock that may result in display flicker. It is recommended to configure the device to force Single or Dual Lane mode of operation.