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Propagated clock for reg2out

Aram Shahinyan

Dear Friends,

I'm looking into Solution with ID 11327942. Can't figure out how clock latency 2.5ns is decided for reg2out paths

set_clock_latency 2.5 -rise clk2

 Can you please give me a hint?

 Thanks,

Aram

Parents

  • Aram

    We always referenced ip / op delays relative to a "virtual" clock.
    This virtual clock must track the real clock before and after CTS.
    You can automatically update the virtual clock after CTS with the command update_io_latency.
    I know this whole flow / syntax sucks, but primeTime has been doing it this way since the beginning of time.

    Cadence  set_output_delay supports -reference_pin pin_name syntax which would be perfect IF pt_shell also supported it.

    Shawn

     

    preCTS ideal .............................................
    create_clock -name LINE_CLK -period 3.236 -waveform { 0 1.618 } [get_ports {i_LINE_CLK}]
    set_clock_transition         0.150 [get_clocks {LINE_CLK}]
    set_clock_uncertainty -setup 0.110 [get_clocks {LINE_CLK}]
    set_clock_latency            2.200 [get_clocks {LINE_CLK}]

    create_clock -name LINE_VIRT_CLK -period 3.236 -waveform { 0 1.618 }
    set_clock_transition         0.150 [get_clocks {LINE_VIRT_CLK}]
    set_clock_uncertainty -setup 0.110 [get_clocks {LINE_VIRT_CLK}]
    set_clock_latency            2.200 [get_clocks {LINE_VIRT_CLK}]

    set_output_delay  1.6 -clock [get_clocks {LINE_VIRT_CLK}]  [get_ports {ov_fltr_y_din[1537]}]


    postCTS propagated & virtual clock updated .............................................
    create_clock -name LINE_CLK -period 3.236 -waveform { 0 1.618 } [get_ports {i_LINE_CLK}]
    set_clock_transition         0.150 [get_clocks {LINE_CLK}]
    set_clock_uncertainty -setup 0.110 [get_clocks {LINE_CLK}]
    set_propagated_clock               [get_clocks {LINE_CLK}]


    create_clock -name LINE_VIRT_CLK -period 3.236 -waveform { 0 1.618 }
    set_clock_transition         0.150 [get_clocks {LINE_VIRT_CLK}]
    set_clock_uncertainty -setup 0.110 [get_clocks {LINE_VIRT_CLK}]
    set_clock_latency -fall 1.99566  [get_clocks {LINE_VIRT_CLK}]
    set_clock_latency -rise 1.97041  [get_clocks {LINE_VIRT_CLK}]

    set_output_delay  1.6 -clock [get_clocks {LINE_VIRT_CLK}]  [get_ports {ov_fltr_y_din[1537]}]
     

Reply

  • Aram

    We always referenced ip / op delays relative to a "virtual" clock.
    This virtual clock must track the real clock before and after CTS.
    You can automatically update the virtual clock after CTS with the command update_io_latency.
    I know this whole flow / syntax sucks, but primeTime has been doing it this way since the beginning of time.

    Cadence  set_output_delay supports -reference_pin pin_name syntax which would be perfect IF pt_shell also supported it.

    Shawn

     

    preCTS ideal .............................................
    create_clock -name LINE_CLK -period 3.236 -waveform { 0 1.618 } [get_ports {i_LINE_CLK}]
    set_clock_transition         0.150 [get_clocks {LINE_CLK}]
    set_clock_uncertainty -setup 0.110 [get_clocks {LINE_CLK}]
    set_clock_latency            2.200 [get_clocks {LINE_CLK}]

    create_clock -name LINE_VIRT_CLK -period 3.236 -waveform { 0 1.618 }
    set_clock_transition         0.150 [get_clocks {LINE_VIRT_CLK}]
    set_clock_uncertainty -setup 0.110 [get_clocks {LINE_VIRT_CLK}]
    set_clock_latency            2.200 [get_clocks {LINE_VIRT_CLK}]

    set_output_delay  1.6 -clock [get_clocks {LINE_VIRT_CLK}]  [get_ports {ov_fltr_y_din[1537]}]


    postCTS propagated & virtual clock updated .............................................
    create_clock -name LINE_CLK -period 3.236 -waveform { 0 1.618 } [get_ports {i_LINE_CLK}]
    set_clock_transition         0.150 [get_clocks {LINE_CLK}]
    set_clock_uncertainty -setup 0.110 [get_clocks {LINE_CLK}]
    set_propagated_clock               [get_clocks {LINE_CLK}]


    create_clock -name LINE_VIRT_CLK -period 3.236 -waveform { 0 1.618 }
    set_clock_transition         0.150 [get_clocks {LINE_VIRT_CLK}]
    set_clock_uncertainty -setup 0.110 [get_clocks {LINE_VIRT_CLK}]
    set_clock_latency -fall 1.99566  [get_clocks {LINE_VIRT_CLK}]
    set_clock_latency -rise 1.97041  [get_clocks {LINE_VIRT_CLK}]

    set_output_delay  1.6 -clock [get_clocks {LINE_VIRT_CLK}]  [get_ports {ov_fltr_y_din[1537]}]
     

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