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Comment: add information of using GCK for ULTRA + how to implement clock switch/mux

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  1. Use a pad directly connected to the closest CKG (these pads are suffixed by _CLK). Either the user instantiates a PLL or a WFG in the design or the tool instantiates automatically a WFG in bypass mode.

    1. MEDIUM/LARGE: Use a common pad or internal logic and use a buffer NX_BD in global_lowskew mode.

    2. ULTRA: Use a common pad or internal logic and use a NX_GCK_U in Common to System Converter CSC mode.

Please have a look at Training Package : Application Note Design/LowskewManagement project.

In case of clock gating or clock mux, it is recommended to implement the following architecture:

  • Clock Gating:

    • MEDIUM/LARGE: Use a NX_CKS to gate a clock system signals with a command common signal.

    • ULTRA: Use a NX_GCK_U in Clock Switch CKS mode to gate a clock system signals with a command common signal.

  • Clock MUX:

    • ULTRA: Use a NX_GCK_U in Clock MUX MUX mode to switch between 2 clock system signals with a command common signal.

Reset management

Like clocks, reset are generally spread to the whole design through the low-skew network because of high fanout too.

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The logic depth of a design must be controlled. the method reportDesignComplexity is very helpful to have an overview.

It

Please have a look at NxBeta_NXpython specification Impulse 23.1 NxPython Specification reportDesignComplexity method.

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