6.2.1. Clock Signals
|ext_core_clk||Input||Core clock. Output of user-instantiated I/O PLL. The HBM2 IP does not instantiate the I/O PLL required to generate the ext_core_clk.
When the core clock frequency is one-half of the HBM2 interface frequency, the reference clock that drives the core I/O PLL must come from the same oscillator as that supplying the UIB PLL reference clock on the board for a given HBM2 interface. Failure to follow this guideline can result in calibration not completing successfully or the AXI bus locking up.
Although you can set the core clock frequency to a maximum of one-half of the memory clock, Intel® recommends not exceeding the recommended core clock limits presented in Table 9 to avoid potential timing closure problems.
|ext_core_clk_locked||Input||LOCKED status of I/O PLL driving ext_core_clk, indicating the ext_core_clk is stable. This I/O PLL should achieve LOCKED status within 1ms of device configuration for calibration to be successful. The I/O PLL driving the ext_core_clk cannot be reset after calibration is completed.|
|pll_ref_clk||Input||LVDS reference clock input for UIB PLL. This reference clock must be provided through dedicated UIB_PLL_REF_CLK_p/n pins available in Intel® Stratix® 10 devices and cannot be provided through an internal I/O PLL. The pll_ref_clk must be stable and free-running at device power-up for successful configuration. Refer to Intel® Stratix® 10 pin connection guidelines for information on how to supply these clocks.|
Core clock output feedback from UIB, based on ext_core_clk provided, one per HBM2 Channel (represented by x).
Intel® recommends that the user interface drive the AXI interface for the corresponding channels with this clock.
|phy_clk_x_clk||Output||UIB PHY clk output. Not supported. Leave unconnected. This signal appears as phy_clk_x conduit in the Platform Designer.|
Clocking recommendations for Reliable Calibration of the HBM2 Interface
Observe the following clock guidelines for reliable calibration of the HBM2 interface:
- The UIB PLL reference clocks (one per HBM2 interface) must be provided through an external clock source and must be stable and free running prior to configuration and stable thereafter.
- The I/O PLL driving the core clock (ext_core_clk) should achieve a LOCKED condition within one millisecond of device configuration. This I/O PLL cannot be reset once the interface is calibrated.
- For a given HBM2 interface, Intel® recommends that the same clock source provide the reference clocks for both the I/O PLL and the UIB PLL.
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