SPRUIE9D May 2017 – May 2024 DRA74P , DRA75P , DRA76P , DRA77P
[New DRA7xxP feature versus DRA75x/DRA74x]
To support 4096Fs the frequency of the MLB clock line is doubled using a delay line and XOR gate. The delay line is composed by two DLLs and ratio logic as shown in Figure 26-230. The master DLL (MDLL) provides a code which is passed to the ratio logic. The ratio logic modifies that code to provide acceptable for the slave delay line (SDL) code. The code modification is performed based on the value of the CTRL_CORE_MLB_DLL_REG[27:20] DLL_RATIO bit field. The value which has to be loaded in the DLL_RATIO bit field is calculated based on the following equation: DLL_RATIO = (2,5/MP)*256, where MP is the MDLL clock period measured in ns. For example, if MP = 3,75ns, the DLL_RATIO = (2,5/3,75)*256 = 170,66. Therefore DLL_RATIO = 0xAA.
The delay line produces a quarter cycle shift of the SDL output clock (CLKOUT) to its input clock (CLKIN). After passing CLKIN and CLKOUT to a XOR gate the frequency is doubled. There is an option to select the MLB clock line frequency to be equal to CLKIN or to it's doubled version. This is controlled by the CTRL_CORE_MLB_DLL_REG[31] CLK_SEL_MLB bit.
The CTRL_CORE_MLB_DLL_REG[29] DLL_LOCK bit indicates that the MDLL has locked to its reference clock. This is done when the DLL_LOCK bit asserts to 0x1. Once high, it will remain high till the MDLL is reset. CTRL_CORE_MLB_DLL_REG[28] SDL_LOCK = 0x1 indicates that the SDL has been updated with a code. This bit remains high till the SDL is reset.
The MDLL and the ratio logic are clocked by the L3MAIN1_L3_GICLK clock (called also MDLL reference clock). For more details about the L3MAIN1_L3_GICLK see Power, Reset, and Clock Management and the device Data Manual. The CM_CORE_AON_RST is the reset signal for the MDLL and SDL. The L3MAIN1_L3_GICLK clock can be enabled or disabled (not from PRCM side but from MDLL side) using the CTRL_CORE_MLB_DLL_REG[30] DLL_CLOCK_DISABLE bit.
The CTRL_CORE_MLB_DLL_REG register is from the Control Module.