The FlatLink LVDS clock may be derived from the DSI channel A clock, or from an external reference clock source. When the MIPI D-PHY channel A HS clock is used as the LVDS clock source, the D-PHY clock lane must operate in HS free-running (continuous) mode. This feature eliminates the need for an external reference clock reducing system costs

The reference clock source is selected by HS_CLK_SRC (CSR 0x0A.0) programmed through the local I²C interface. If an external reference clock is selected, it is multiplied by the factor in REFCLK_MULTIPLIER (CSR 0x0B.1:0) to generate the FlatLink LVDS output clock. When an external reference clock is selected, it must be between 25 MHz and 154 MHz. If the DSI channel A clock is selected, it is divided by the factor in DSI_CLK_DIVIDER (CSR 0x0B.7:3) to generate the FlatLink LVDS output clock. Additionally, LVDS_CLK_RANGE (CSR 0x0A.3:1) and CH_DSI_CLK_RANGE(CSR 0x12) must be set to the frequency range of the FlatLink LVDS output clock and DSI Channel A input clock respectively for the internal PLL to operate correctly. After these settings are programmed, PLL_EN (CSR 0x0D.0) must be set to enable the internal PLL.