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Altera_Forum's avatar
Altera_Forum
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16 years ago

create_clock .sdc syntax

Hi,

I am trying to specify a period constraint to input_clk[1] port of a PLL.

Every example I can find shows:

create_clock -period 10.000 -name clk [get_ports {clk}]

The issue is that I have two PLLs which have the same port names.. so how do I modify the [get_ports{clk}] parameter to specify a specific PLL port?

I've tried including a specific instance name but TA barfed... Any ideas?

thx

2 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    From what I understand, ports are a top-level entity concept from the timing analyzer's perspective. So, when you refer to [get_ports {clk}], the timing analyzer is looking for an I/O port on your top-level entity called clk. Ports of internal instances, like your PLL, are pins from the timing analyzer's perspective. In order to create a clock on your PLL input source, you can either create the clock on the T/L entity port using the syntax you described or you can create the clock on the PLL instance port/pin using something like [get pins {<hierarchical_path_to_pll>/<pll_clk_pin>}].

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor

    --- Quote Start ---

    Hi,

    I am trying to specify a period constraint to input_clk[1] port of a PLL.

    Every example I can find shows:

    create_clock -period 10.000 -name clk [get_ports {clk}]

    The issue is that I have two PLLs which have the same port names.. so how do I modify the [get_ports{clk}] parameter to specify a specific PLL port?

    I've tried including a specific instance name but TA barfed... Any ideas?

    thx

    --- Quote End ---

    Hi,

    have look to the small attached project. Maybe it will answer your question.

    Kind regards

    GPK