{"sections":[{"code":".TRAN time_step stop_time [print_start_time] [print_step] [UIC] [STARTUP|DST]","heading":"Keep integration and output sampling distinct","paragraphs":["For the fixed-step example, time_step controls integration and print_step sets the requested output cadence. print_start_time hides earlier waveform output. Omitting print_step emits accepted simulation samples; an explicit print_step must be positive.","The optional startup/initial-condition flags have separate meanings. Keep those settings and the circuit fixed during refinement. Adaptive stepping has additional controls and supported-analysis restrictions; this example checks fixed-step VOLTAGE/BDF only."]},{"code":"* RC response: 50 ohm, 0.2 pF, 10 ps time constant\n.PARAM DRIVE=1m\nV1 IN 0 PWL(0 0 10p 0 20p DRIVE 100p DRIVE)\nR1 IN OUT 50\nC1 OUT 0 0.2p\n.OPTION ANALYSIS=VOLTAGE INTEGRATION=BDF\n.TRAN 0.5p 100p 0 2p\n.PRINT V(IN) V(OUT) I(R1)\n.END","heading":"Create a common-grid RC comparison","paragraphs":["Save the complete RC deck below as rc_coarse.cir. Copy it to rc_medium.cir and rc_fine.cir; change only the first .TRAN argument to 0.25p and 0.125p respectively. Keep stop time 100p, print start 0 and print step 2p in all three."]},{"code":"josim-pro-cli -o rc_coarse.csv rc_coarse.cir\njosim-pro-cli -o rc_medium.csv rc_medium.cir\njosim-pro-cli -o rc_fine.csv rc_fine.cir","heading":"Run to three separate outputs","steps":["Confirm each run succeeds and each CSV is new.","Compare V(OUT) at the common output times and check peak values, threshold times or other required measurements. Keep units and source amplitude consistent.","Compare with the independent RC expression in the netlist guide. For this check the error window is 24–80 ps, away from the input-ramp corners."]},{"heading":"Interpret the checked refinement","paragraphs":["All three checked CSV files contain 51 samples over 0–100 ps because the output cadence is 2 ps. The integration steps differ even though the output row counts match.","Maximum absolute V(OUT) error in the declared window fell from approximately 0.3607 microvolt at 0.5 ps to 0.0860 microvolt at 0.25 ps and 0.0210 microvolt at 0.125 ps. The comparison is against this ideal RC reference, not against another run treated as ground truth.","For a real circuit, set tolerances on its actual outputs or measured quantities, refine until those criteria and relevant model/reference checks are met, and record the remaining error. Preserve physical-model, startup, seed and stimulus settings. Do not transfer this RC result or its tolerance to a Josephson, noisy or transmission-line circuit."]},{"heading":"Recover from an invalid output step","paragraphs":["An explicit zero print_step was rejected without CSV in the checked runtime. Remove that optional argument to emit accepted steps, or supply a positive cadence and rerun to a fresh filename.","If refinements disagree, inspect discontinuities, analysis/integration mode, initial conditions, model validity and output interpolation. Increasing file precision or decreasing print_step alone does not resolve integration error."]}],"canonical_url":"https://www.sun-magnetics.com/knowledge-base/josim-transient-timestep","url":"/knowledge-base/josim-transient-timestep","known_issues":[],"search_record":{"execution":true,"relatedProducts":[],"version_tags":["JoSIM-Pro 2.9 target"],"text":"Choose and refine simulation and output time steps Refine the integration step while keeping a common output grid, then compare the quantities that matter. A denser plot export alone does not establish a more accurate simulation. JoSIM-Pro 2.9.0 release target; bounded Windows RC CLI evidence How to simulation timestep output print step time step refinement print cadence RC accuracy .TRAN sampling Keep integration and output sampling distinct For the fixed-step example, time_step controls integration and print_step sets the requested output cadence. print_start_time hides earlier waveform output. Omitting print_step emits accepted simulation samples; an explicit print_step must be positive. The optional startup/initial-condition flags have separate meanings. Keep those settings and the circuit fixed during refinement. Adaptive stepping has additional controls and supported-analysis restrictions; this example checks fixed-step VOLTAGE/BDF only. .TRAN time_step stop_time [print_start_time] [print_step] [UIC] [STARTUP|DST] Create a common-grid RC comparison Save the complete RC deck below as rc_coarse.cir. Copy it to rc_medium.cir and rc_fine.cir; change only the first .TRAN argument to 0.25p and 0.125p respectively. Keep stop time 100p, print start 0 and print step 2p in all three. * RC response: 50 ohm, 0.2 pF, 10 ps time constant\n.PARAM DRIVE=1m\nV1 IN 0 PWL(0 0 10p 0 20p DRIVE 100p DRIVE)\nR1 IN OUT 50\nC1 OUT 0 0.2p\n.OPTION ANALYSIS=VOLTAGE INTEGRATION=BDF\n.TRAN 0.5p 100p 0 2p\n.PRINT V(IN) V(OUT) I(R1)\n.END Run to three separate outputs Confirm each run succeeds and each CSV is new. Compare V(OUT) at the common output times and check peak values, threshold times or other required measurements. Keep units and source amplitude consistent. Compare with the independent RC expression in the netlist guide. For this check the error window is 24–80 ps, away from the input-ramp corners. josim-pro-cli -o rc_coarse.csv rc_coarse.cir\njosim-pro-cli -o rc_medium.csv rc_medium.cir\njosim-pro-cli -o rc_fine.csv rc_fine.cir Interpret the checked refinement All three checked CSV files contain 51 samples over 0–100 ps because the output cadence is 2 ps. The integration steps differ even though the output row counts match. Maximum absolute V(OUT) error in the declared window fell from approximately 0.3607 microvolt at 0.5 ps to 0.0860 microvolt at 0.25 ps and 0.0210 microvolt at 0.125 ps. The comparison is against this ideal RC reference, not against another run treated as ground truth. For a real circuit, set tolerances on its actual outputs or measured quantities, refine until those criteria and relevant model/reference checks are met, and record the remaining error. Preserve physical-model, startup, seed and stimulus settings. Do not transfer this RC result or its tolerance to a Josephson, noisy or transmission-line circuit.  Recover from an invalid output step An explicit zero print_step was rejected without CSV in the checked runtime. Remove that optional argument to emit accepted steps, or supply a positive cadence and rerun to a fresh filename. If refinements disagree, inspect discontinuities, analysis/integration mode, initial conditions, model validity and output interpolation. Increasing file precision or decreasing print_step alone does not resolve integration error. ","id":"josim-transient-timestep","keywords":"simulation timestep output print step time step refinement print cadence RC accuracy .TRAN sampling","kind":"How to","title":"Choose and refine simulation and output time steps","product":"JoSIM-Pro"},"version":"2.9.0 release target; bounded Windows RC CLI evidence","id":"josim-transient-timestep","related":["/knowledge-base/josim-netlist-basics","/knowledge-base/josim-measurements","/knowledge-base/josim-variable-step-lines","/knowledge-base/josim-noise-settings","/knowledge-base/josim-cli-output","/knowledge-base/sparameter-model-handoff"],"downloads":[{"url":"/_functions/kbExample?name=rc-refinement.zip","scope":"Exact checked input files plus instructions; final-release/platform applicability remains pending.","files":["rc_coarse.cir","rc_medium.cir","rc_fine.cir","README.txt"],"id":"rc-refinement","requires":["Compatible licensed JoSIM-Pro 2.9 CLI","New writable directory; preserve all files together"],"title":"RC time-step comparison"}],"publication_status":"published","numerical_output":null,"provenance":{"execution_checks":[{"routes":["cli"],"scope":"Complete linear RC circuit, included parameterised cell, include recovery, fixed-step refinement, nine scalar forms and measurement failure/recovery","result":"passed","articles":["josim-netlist-basics","josim-hierarchical-design","josim-transient-timestep","josim-measurements"],"purpose":"circuit-authoring-refinement-measurements","version":"JoSIM-Pro 2.9.0 installed Windows review CLI","id":"VAL-014","records":["authoring-version","rc_basic","rc_hierarchy","rc_missing_library","rc_library_restored","rc_literal_override","rc_coarse","rc_medium","rc_fine","rc_measurements","rc_measurements_sparse","rc_missing_event","rc_measurements_recovered","rc_duplicate_measurement","rc_invalid_print_step"],"limit":"Handwritten RC examples and their declared analytic criteria only. No Josephson-device, adaptive/noisy, GUI, other-platform or final-release qualification. CLI loaded-library path was not observed.","observed":{"missing_event_rejected_without_final_csv":true,"hierarchy_headers":["time","V(OUT50)","V(OUT100)","I(R1|X1)"],"nonpositive_print_step_rejected":true,"installed_cli_and_adjacent_core_preserved":true,"all_authored_inputs_preserved":true,"measurement_reference_checks":{"delay":true,"swing":true,"peak":true,"half":true,"rms":true,"integral":true,"sample":true,"average":true,"minimum":true},"missing_include_rejected_without_csv":true,"measurements":{"delay":{"unit":"s","value":7.347845185494056e-12},"swing":{"unit":"V","value":0.00008397118684255278},"peak":{"unit":"V","value":0.000998434674734019},"half":{"unit":"s","value":2.2347845185494056e-11},"rms":{"unit":"V","value":0.0009792524152708322},"integral":{"unit":"V*s","value":3.916042272290987e-14},"sample":{"unit":"V","value":0.0009685395593167445},"average":{"unit":"V","value":0.0009790105680727468},"minimum":{"unit":"V","value":0.0009144634878914662}},"measurements_independent_of_print_start_and_cadence":true,"nine_scalar_values_and_units_match_reference":true,"complete_basic_circuit_matches_rc_reference":true,"duplicate_case_insensitive_name_rejected":true,"sparse_measurements":{"delay":{"unit":"s","value":7.347845185494056e-12},"swing":{"unit":"V","value":0.00008397118684255278},"peak":{"unit":"V","value":0.000998434674734019},"half":{"unit":"s","value":2.2347845185494056e-11},"rms":{"unit":"V","value":0.0009792524152708322},"integral":{"unit":"V*s","value":3.916042272290987e-14},"sample":{"unit":"V","value":0.0009685395593167445},"average":{"unit":"V","value":0.0009790105680727468},"minimum":{"unit":"V","value":0.0009144634878914662}},"literal_component_value_not_changed_by_unused_named_argument":true,"analytic_reference":{"delay":{"absolute_check_allowance":5e-14,"unit":"s","value":7.344720351728633e-12},"swing":{"absolute_check_allowance":0.000002,"unit":"V","value":0.00008398134465763686},"peak":{"absolute_check_allowance":0.000002,"unit":"V","value":0.0009984331297888881},"half":{"absolute_check_allowance":5e-14,"unit":"s","value":2.2344720351728633e-11},"rms":{"absolute_check_allowance":0.000002,"unit":"V","value":0.000979246563904772},"integral":{"absolute_check_allowance":8e-17,"unit":"V*s","value":3.916018655342363e-14},"sample":{"absolute_check_allowance":0.000002,"unit":"V","value":0.0009685285705208703},"average":{"absolute_check_allowance":0.000002,"unit":"V","value":0.0009790046638355908},"minimum":{"absolute_check_allowance":0.000002,"unit":"V","value":0.0009144517851312513}},"refinement_reduces_reference_error":true,"refinement":{"coarse":{"step":"0.5p","max_voltage_error_V":3.607179059673428e-7,"max_error_fraction_of_drive":0.0003607179059673428,"headers":["time","V(IN)","V(OUT)","I(R1)"],"rows":51,"time_start_s":0,"time_end_s":1e-10},"fine":{"step":"0.125p","max_voltage_error_V":2.1017905967295886e-8,"max_error_fraction_of_drive":0.000021017905967295886,"headers":["time","V(IN)","V(OUT)","I(R1)"],"rows":51,"time_start_s":0,"time_end_s":1e-10},"medium":{"step":"0.25p","max_voltage_error_V":8.601790596734354e-8,"max_error_fraction_of_drive":0.00008601790596734354,"headers":["time","V(IN)","V(OUT)","I(R1)"],"rows":51,"time_start_s":0,"time_end_s":1e-10}},"restoring_reachable_event_recovers_measurements_and_csv":true,"corrected_include_reference_recovers":true,"three_refinements_keep_51_common_output_samples":true,"successful_commands_exit_zero":true,"measurement_csv":{"headers":["time","V(IN)","V(OUT)","I(R1)"],"rows":31,"time_start_s":4e-11},"included_subcircuit_and_instance_override":true}}],"figure_evidence":[],"review_notes":["The documented RC files match the checked input content. All new outputs were written to fresh paths.","Final distributed 2.9 package, other platforms and GUI workflows remain pending. Example-specific analytic allowances are not universal solver tolerances."],"scope":"Recorded inputs/builds only. Complete walkthrough and final-package acceptance remain separate.","verification_requirements":{"gui_method":"not-required-for-this-answer","illustrations":"not-required-for-this-answer","required":["technical-review","release-applicability","execution","numerical-interpretation","recovery"],"status":"review-incomplete"},"sources":[{"id":"josim-pro:docs/manual_source/sections/syntax.tex","section":"Transient analysis, print start/cadence, startup flags and runtime/integration restrictions"},{"id":"josim-pro:docs/manual_source/sections/usage.tex","section":"CLI input/output and versioned execution contract"},{"id":"validation:josim-authoring-windows-20261103","section":"VAL-014: exact RC examples, independent reference checks and recovery"}]},"title":"Choose and refine simulation and output time steps","type":"How to","markdown_url":"/_functions/kbResource?path=markdown%2Fjosim-transient-timestep.md","summary":"Refine the integration step while keeping a common output grid, then compare the quantities that matter. A denser plot export alone does not establish a more accurate simulation.","product":"JoSIM-Pro"}