SPRUI30H November 2015 – May 2024 DRA745 , DRA746 , DRA750 , DRA756
Figure 26-20 is a simplified block diagram of the DPLL_PCIE_REF instance integrated in the PCIe PHY clock generator subsystem.
The input clock CLKINP goes to a predivider N + 1. The entire loop runs on the REFCLK clock after this predivider. The value of N + 1 is controlled through the PRCM.CM_CLKSEL_DPLL_PCIE_REF[7:0] DPLL_DIV bit field.
The frequency ranges for the DPLL_PCIE_REF input clock - CLKINP and the DPLL internal reference clock, REFCLK = CLKINP/N + 1 are:
The output clock CLKOUTLDO is synthesized by digitally controlled oscillator (the DCO block), that automatically detects the frequency range divided by the M2 value. The CLKOUTLDO frequency can be given with CLKOUTLDO = [CLKINP×M/(N + 1)]/M2. For that purpose the feedback multiplier M must be configured through the PRCM.CM_CLKSEL_DPLL_PCIE_REF[19:8] DPLL_MULT bit field and the output clock divider M2 must be configured through the PRCM.CM_DIV_M2_DPLL_PCIE_REF[6:0] DIVHS bit field.
Fractional synthesis is not supported for M.