Address a few typos in docs related to SSTA (#447)
* Address a few typos in docs Signed-off-by: dsengupta0628 <dsengupta@precisioninno.com> * update help string for report_checks to reflect variation Signed-off-by: dsengupta0628 <dsengupta@precisioninno.com> --------- Signed-off-by: dsengupta0628 <dsengupta@precisioninno.com>
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Deepashree Sengupta
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@ -22,13 +22,13 @@ Release 3.0.1 2026/03/12
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------------------------
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Statistical timing (SSTA) with Liberty LVF (Liberty Variation Format)
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models is now supported. Statistical timing uses a probaility
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distribution to represent a delay or slew ranther than a single
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models is now supported. Statistical timing uses a probability
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distribution to represent a delay or slew rather than a single
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number.
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Normal and skew normal probability distributions are supported.
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SSTA is enabled with the sta_pocv_mode variaable.
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SSTA is enabled with the sta_pocv_mode variable.
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set sta_pocv_mode scalar|normal|skew_normal
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@ -43,10 +43,10 @@ set with the sta_pocv_quantile variable.
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The default value is 3 standard deviations, or sigma.
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Use the variance field with report_checks or report_check_types to see
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Use the variation field with report_checks or report_check_types to see
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distribution parameters in timing reports.
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A command file for analyzing a design with statisical timing with an
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A command file for analyzing a design with statistical timing with an
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LVF library is shown below.
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read_liberty lvf_library.lib.gz
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@ -6639,15 +6639,15 @@
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<text:p text:style-name="P17">This example can be found in <text:span text:style-name="T8">examples/</text:span><text:span text:style-name="T10">mcmm3</text:span><text:span text:style-name="T8">.tcl</text:span>.<text:line-break/><text:line-break/><text:span text:style-name="T6">In the example show above the SDC for the modes is in separate files. Alternatively, the SDC can be defined in the command file using the </text:span><text:span text:style-name="T13">set_mode</text:span><text:span text:style-name="T6"> command between SDC command groups.</text:span></text:p>
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<text:p text:style-name="P18"><text:span text:style-name="T6">set_mode mode1<text:line-break/>create_clock -name m1_clk -period 1000 {clk1 clk2 clk3}<text:line-break/></text:span>set_input_delay -clock m1_clk 100 {in1 in2}<text:line-break/><text:line-break/><text:span text:style-name="T6">set_mode mode2<text:line-break/>create_clock -name m2_clk -period 500 {clk1 clk3}<text:line-break/></text:span>set_output_delay -clock m2_clk 100 out</text:p>
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<text:h text:style-name="P19" text:outline-level="2"><text:bookmark-start text:name="__RefHeading___Toc42583_2528141652 Copy 1"/>Statistical Timing Analysis<text:bookmark-end text:name="__RefHeading___Toc42583_2528141652 Copy 1"/></text:h>
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<text:p text:style-name="Body_20_first">OpenSTA also supports <text:span text:style-name="T14">statistical timing </text:span>.<text:span text:style-name="T14">anallysis with Liberty Variation Format (LVF) libraries. Statistical timing uses a probaility </text:span>distribution to represent a delay or slew ranther than a single number.</text:p>
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<text:p text:style-name="P20"><text:soft-page-break/>Normal and skew normal probability distributions are supported. <text:s/>SSTA is enabled with the <text:span text:style-name="T12">sta_pocv_mode</text:span> variaable.</text:p>
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<text:p text:style-name="Body_20_first">OpenSTA also supports <text:span text:style-name="T14">statistical timing </text:span><text:span text:style-name="T14">analysis with Liberty Variation Format (LVF) libraries. Statistical timing uses a probability </text:span>distribution to represent a delay or slew rather than a single number.</text:p>
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<text:p text:style-name="P20"><text:soft-page-break/>Normal and skew normal probability distributions are supported. <text:s/>SSTA is enabled with the <text:span text:style-name="T12">sta_pocv_mode</text:span> variable.</text:p>
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<text:p text:style-name="Example_20__20_indented">set sta_pocv_mode scalar|normal|skew_normal<text:line-break/><text:line-break/><text:span text:style-name="T15">scalar mode is for non-SSTA analysis<text:line-break/>normal mode uses gaussian normal distributions<text:line-break/>skew_normal mode is for skew normal LVF moment based distributions</text:span></text:p>
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<text:p text:style-name="P20">The target quantile of a delay probability distribution (confidence level) is set with the <text:span text:style-name="T12">sta_pocv_quantile</text:span> variable.</text:p>
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<text:p text:style-name="Example_20__20_indented"><text:span text:style-name="T16">set </text:span>sta_pocv_quantile <float></text:p>
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<text:p text:style-name="P20">The default value is 3 standard deviations, or sigma.</text:p>
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<text:p text:style-name="P21"><text:span text:style-name="T16">Use the </text:span><text:span text:style-name="T12">variance</text:span> <text:span text:style-name="T16">field with the </text:span>report_checks <text:span text:style-name="T16">and</text:span> report_check_types <text:span text:style-name="T16">commands to see distribution parameters in timing reports.</text:span></text:p>
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<text:p text:style-name="P22">A command file for analyzing a design with statisical timing is shown below.</text:p>
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<text:p text:style-name="Example_20__20_indented"><text:soft-page-break/>read_liberty lvf_library.lib.gz<text:line-break/>read_verilog design.v<text:line-break/>link_design topcreate_clock -period 50 clk<text:line-break/>set_input_delay -clock clk 1 {in1 in2}<text:line-break/>set sta_pocv_mode skew_normal<text:line-break/>report_checks -fields {slew variation input_pin variation} -digits 3</text:p>
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<text:p text:style-name="P21"><text:span text:style-name="T16">Use the </text:span><text:span text:style-name="T12">variation</text:span> <text:span text:style-name="T16">field with the </text:span>report_checks <text:span text:style-name="T16">and</text:span> report_check_types <text:span text:style-name="T16">commands to see distribution parameters in timing reports.</text:span></text:p>
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<text:p text:style-name="P22">A command file for analyzing a design with statistical timing is shown below.</text:p>
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<text:p text:style-name="Example_20__20_indented"><text:soft-page-break/>read_liberty lvf_library.lib.gz<text:line-break/>read_verilog design.v<text:line-break/>link_design topcreate_clock -period 50 clk<text:line-break/>set_input_delay -clock clk 1 {in1 in2}<text:line-break/>set sta_pocv_mode skew_normal<text:line-break/>report_checks -fields {slew variation input_pin} -digits 3</text:p>
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<text:p text:style-name="Example_20__20_indented"><text:soft-page-break/><text:span text:style-name="T16">Startpoint: r2 (rising edge-triggered flip-flop clocked by clk)<text:line-break/>Endpoint: r3 (rising edge-triggered flip-flop clocked by clk)<text:line-break/>Path Group: clk<text:line-break/>Path Type: max<text:line-break/><text:line-break/> <text:s text:c="3"/>Slew <text:s text:c="3"/>Delay Variation <text:s text:c="4"/>Time <text:s text:c="2"/>Description<text:line-break/>---------------------------------------------------------------------------<text:line-break/> <text:s text:c="2"/>0.000 <text:s text:c="3"/>0.000 <text:s text:c="12"/>0.000 <text:s text:c="2"/>clock clk (rise edge)<text:line-break/> <text:s text:c="11"/>0.000 <text:s text:c="12"/>0.000 <text:s text:c="2"/>clock network delay (ideal)<text:line-break/> <text:s text:c="2"/>0.000 <text:s text:c="3"/>0.000 <text:s text:c="12"/>0.000 ^ r2/CK (FDPQ1)<text:line-break/> <text:s text:c="19"/>12.026 <text:s text:c="11"/>mean<text:line-break/> <text:s text:c="20"/>0.017 <text:s text:c="11"/>mean_shift<text:line-break/> <text:s text:c="20"/>0.366 <text:s text:c="11"/>std_dev<text:line-break/> <text:s text:c="20"/>0.000 <text:s text:c="11"/>skewness<text:line-break/> <text:s text:c="2"/>4.648 <text:s text:c="2"/>12.409 <text:s text:c="11"/>12.409 v r2/Q (FFQ1)<text:line-break/> <text:s text:c="2"/>4.648 <text:s text:c="3"/>0.000 <text:s text:c="11"/>12.409 v u1/A (BUF1)<text:line-break/> <text:s text:c="20"/>6.084 <text:s text:c="11"/>mean<text:line-break/> <text:s text:c="20"/>0.007 <text:s text:c="11"/>mean_shift<text:line-break/> <text:s text:c="20"/>0.188 <text:s text:c="11"/>std_dev<text:line-break/> <text:s text:c="20"/>0.000 <text:s text:c="11"/>skewness<text:line-break/> <text:s text:c="2"/>2.513 <text:s text:c="3"/>6.137 <text:s text:c="11"/>18.546 v u1/X (BUF1)<text:line-break/> <text:s text:c="2"/>2.513 <text:s text:c="3"/>0.000 <text:s text:c="11"/>18.546 v u2/A2 (AN21)<text:line-break/> <text:s text:c="20"/>6.447 <text:s text:c="11"/>mean<text:line-break/> <text:s text:c="20"/>0.008 <text:s text:c="11"/>mean_shift<text:line-break/> <text:s text:c="20"/>0.191 <text:s text:c="11"/>std_dev<text:line-break/> <text:s text:c="20"/>0.000 <text:s text:c="11"/>skewness<text:line-break/> <text:s text:c="2"/>2.565 <text:s text:c="3"/>6.497 <text:s text:c="11"/>25.043 v u2/X (AN21)<text:line-break/> <text:s text:c="2"/>2.565 <text:s text:c="3"/>0.000 <text:s text:c="11"/>25.043 v r3/D (FFQ1)<text:line-break/> <text:s text:c="28"/>25.043 <text:s text:c="2"/>data arrival time<text:line-break/></text:span><text:line-break/> <text:s text:c="2"/>0.000 <text:s text:c="2"/>50.000 <text:s text:c="11"/>50.000 <text:s text:c="2"/>clock clk (rise edge)<text:line-break/> <text:s text:c="11"/>0.000 <text:s text:c="11"/>50.000 <text:s text:c="2"/>clock network delay (ideal)<text:line-break/> <text:s text:c="11"/>0.000 <text:s text:c="11"/>50.000 <text:s text:c="2"/>clock reconvergence pessimism<text:line-break/> <text:s text:c="28"/>50.000 ^ r3/CK (FFQ1)<text:line-break/> <text:s text:c="10"/>-9.376 <text:s text:c="11"/>40.624 <text:s text:c="2"/>library setup time<text:line-break/> <text:s text:c="28"/>40.624 <text:s text:c="2"/>data required time<text:line-break/>---------------------------------------------------------------------------<text:line-break/> <text:s text:c="28"/>40.624 <text:s text:c="2"/>data required time<text:line-break/> <text:s text:c="27"/>-25.043 <text:s text:c="2"/>data arrival time<text:line-break/>---------------------------------------------------------------------------<text:line-break/> <text:s text:c="28"/>15.581 <text:s text:c="2"/>slack (MET)</text:p>
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<text:p text:style-name="P23">The standard deviation for <text:span text:style-name="T14">n</text:span>ormal distributions is specified with the following liberty timing groups.</text:p>
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<text:p text:style-name="P24"><text:soft-page-break/>ocv_sigma_cell_rise<text:line-break/>ocv_sigma_cell_fall<text:line-break/>ocv_sigma_rise_transition<text:line-break/>ocv_sigma_fall_transition<text:line-break/>ocv_sigma_rise_constraint<text:line-break/>ocv_sigma_fall_constraint</text:p>
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@ -9532,7 +9532,7 @@
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<text:p text:style-name="P160">fields</text:p>
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</table:table-cell>
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<table:table-cell table:style-name="Table52.A2" office:value-type="string">
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<text:p text:style-name="P151"><text:span text:style-name="Default_20_Paragraph_20_Font">List of </text:span><text:span text:style-name="Default_20_Paragraph_20_Font"><text:span text:style-name="T12">capacitance|slew|input_pins|</text:span></text:span><text:span text:style-name="Default_20_Paragraph_20_Font"><text:span text:style-name="T173">hierarc</text:span></text:span><text:span text:style-name="Default_20_Paragraph_20_Font"><text:span text:style-name="T174">h</text:span></text:span><text:span text:style-name="Default_20_Paragraph_20_Font"><text:span text:style-name="T173">i</text:span></text:span><text:span text:style-name="Default_20_Paragraph_20_Font"><text:span text:style-name="T174">c</text:span></text:span><text:span text:style-name="Default_20_Paragraph_20_Font"><text:span text:style-name="T173">al_pins|</text:span></text:span><text:span text:style-name="Default_20_Paragraph_20_Font"><text:span text:style-name="T12">nets|fanout</text:span></text:span><text:span text:style-name="Default_20_Paragraph_20_Font"><text:span text:style-name="T175">|src_attr</text:span></text:span><text:span text:style-name="Default_20_Paragraph_20_Font"><text:span text:style-name="T176">|variance</text:span></text:span></text:p>
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<text:p text:style-name="P151"><text:span text:style-name="Default_20_Paragraph_20_Font">List of </text:span><text:span text:style-name="Default_20_Paragraph_20_Font"><text:span text:style-name="T12">capacitance|slew|input_pins|</text:span></text:span><text:span text:style-name="Default_20_Paragraph_20_Font"><text:span text:style-name="T173">hierarc</text:span></text:span><text:span text:style-name="Default_20_Paragraph_20_Font"><text:span text:style-name="T174">h</text:span></text:span><text:span text:style-name="Default_20_Paragraph_20_Font"><text:span text:style-name="T173">i</text:span></text:span><text:span text:style-name="Default_20_Paragraph_20_Font"><text:span text:style-name="T174">c</text:span></text:span><text:span text:style-name="Default_20_Paragraph_20_Font"><text:span text:style-name="T173">al_pins|</text:span></text:span><text:span text:style-name="Default_20_Paragraph_20_Font"><text:span text:style-name="T12">nets|fanout</text:span></text:span><text:span text:style-name="Default_20_Paragraph_20_Font"><text:span text:style-name="T175">|src_attr</text:span></text:span><text:span text:style-name="Default_20_Paragraph_20_Font"><text:span text:style-name="T176">|variation</text:span></text:span></text:p>
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</table:table-cell>
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</table:table-row>
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<table:table-row table:style-name="Table52.1">
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@ -9611,7 +9611,7 @@
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<text:p text:style-name="P167">fields</text:p>
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</table:table-cell>
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<table:table-cell table:style-name="Table59.A2" office:value-type="string">
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<text:p text:style-name="P164"><text:span text:style-name="Default_20_Paragraph_20_Font">List of </text:span><text:span text:style-name="Default_20_Paragraph_20_Font"><text:span text:style-name="T12">capacitance|slew|input_pins|</text:span></text:span><text:span text:style-name="Default_20_Paragraph_20_Font"><text:span text:style-name="T173">hierarc</text:span></text:span><text:span text:style-name="Default_20_Paragraph_20_Font"><text:span text:style-name="T174">h</text:span></text:span><text:span text:style-name="Default_20_Paragraph_20_Font"><text:span text:style-name="T173">i</text:span></text:span><text:span text:style-name="Default_20_Paragraph_20_Font"><text:span text:style-name="T174">c</text:span></text:span><text:span text:style-name="Default_20_Paragraph_20_Font"><text:span text:style-name="T173">al_pins|</text:span></text:span><text:span text:style-name="Default_20_Paragraph_20_Font"><text:span text:style-name="T12">nets|fanout</text:span></text:span><text:span text:style-name="Default_20_Paragraph_20_Font"><text:span text:style-name="T175">|src_attr</text:span></text:span><text:span text:style-name="Default_20_Paragraph_20_Font"><text:span text:style-name="T176">|variance</text:span></text:span></text:p>
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<text:p text:style-name="P164"><text:span text:style-name="Default_20_Paragraph_20_Font">List of </text:span><text:span text:style-name="Default_20_Paragraph_20_Font"><text:span text:style-name="T12">capacitance|slew|input_pins|</text:span></text:span><text:span text:style-name="Default_20_Paragraph_20_Font"><text:span text:style-name="T173">hierarc</text:span></text:span><text:span text:style-name="Default_20_Paragraph_20_Font"><text:span text:style-name="T174">h</text:span></text:span><text:span text:style-name="Default_20_Paragraph_20_Font"><text:span text:style-name="T173">i</text:span></text:span><text:span text:style-name="Default_20_Paragraph_20_Font"><text:span text:style-name="T174">c</text:span></text:span><text:span text:style-name="Default_20_Paragraph_20_Font"><text:span text:style-name="T173">al_pins|</text:span></text:span><text:span text:style-name="Default_20_Paragraph_20_Font"><text:span text:style-name="T12">nets|fanout</text:span></text:span><text:span text:style-name="Default_20_Paragraph_20_Font"><text:span text:style-name="T175">|src_attr</text:span></text:span><text:span text:style-name="Default_20_Paragraph_20_Font"><text:span text:style-name="T176">|variation</text:span></text:span></text:p>
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</table:table-cell>
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</table:table-row>
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<table:table-row table:style-name="Table59.1">
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doc/OpenSTA.pdf
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@ -333,7 +333,7 @@ define_cmd_args "report_checks" \
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[-sort_by_slack]\
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[-path_group group_name]\
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[-format full|full_clock|full_clock_expanded|short|end|slack_only|summary|json]\
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[-fields capacitance|slew|fanout|input_pin|net|src_attr]\
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[-fields capacitance|slew|fanout|input_pin|net|src_attr|variation]\
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[-digits digits]\
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[-no_line_splits]\
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[> filename] [>> filename]}
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