Visible to Intel only — GUID: sfo1410067678661
Ixiasoft
Visible to Intel only — GUID: sfo1410067678661
Ixiasoft
3.3.5. Software Sequenced Clocks
The software sequenced clock groups include additional clocks for peripherals not covered by the NOC clocks. The main purpose is to have a second PLL for the Ethernet 250 MHz clock reference. The following diagram shows the external bypass muxes, hardware-managed external counters and dividers, and clock gates.
There are 3 EMAC cores that have a very strict requirement of either a 250 MHz or 50 MHz clock reference. If the PLL0 frequency is a multiple of 250 MHz (for example 1.5 GHz), driving the EMAC clocks from PLL0 provides PLL1 with more flexibility in VCO clock frequency. In addition, to minimize the PLL clock outputs required, emac_clka can be 250 MHz and emac_clkb can be 50 MHz, allowing each EMAC core to be software configured to select 250 MHz or 50 MHz.
System Clock Name | Frequency | Boot Frequency | Descriptions |
---|---|---|---|
emac{0,1,2}_clk | PLL C2 or PLL C3 | boot_clk | Clock for EMAC. Fixed at 250 MHz or 250 MHz emac_clk and 50 MHz emacb_clk |
emac_ptp_clk | PLL C4 | boot_clk | Clock for EMAC PTP timestamp clock |
gpio_db_clk | 125 Hz to PLL C5 | boot_clk | Clock for GPIO debounce clock |
sdmmc_clk | PLL C6 | boot_clk | Clock for SDMMC |
h2f_user0_clk | PLL C7 | boot_clk | Clock reference for FPGA |
h2f_user1_clk | PLL C8 | boot_clk | Clock reference for FPGA |