Synopsys PrimeTime
Synopsys PrimeTime, the golden signoff STA tool: the flow (netlist, SPEF, SDC, propagated clock, report_timing), PBA, PrimeTime-SI crosstalk, ECO and distributed analysis.
Synopsys PrimeTime (PT) is the industry's golden signoff STA tool, the reference other tools are correlated against. It reads the routed netlist, the extracted parasitics (SPEF), the timing libraries and the SDC, and reports timing with signoff-grade accuracy. PrimeTime-SI adds crosstalk (signal-integrity) analysis, and PrimePower adds power. When a team says timing is "signed off," they usually mean it is clean in PrimeTime across all scenarios.
The PrimeTime flow
Load the .db timing libraries and the routed gate-level netlist, then link the design.
read_parasitics loads the SPEF extracted from the real layout, so net delays are accurate, not estimates.
Source the SDC, then set_propagated_clock so real clock-tree latencies are used.
update_timing, then report_timing / report_constraint to see the worst paths and any violations.
Recover margin with path-based analysis, then generate a timing ECO to fix the last violations.
read_db sky130.db
read_verilog top_routed.v ; link_design top
read_parasitics top.spef ;# real RC from layout
read_sdc top.sdc
set_propagated_clock [all_clocks]
update_timing -full
report_timing -delay_type max -group clk ;# setup
report_timing -delay_type min ;# hold
report_constraint -all_violatorsConcepts worth knowing
- Signoff accuracy, PT is the golden reference; implementation tools correlate their STA back to it.
- PrimeTime-SI, models crosstalk delay and noise from coupling between nets (see Crosstalk & Signal Integrity).
- GBA vs PBA, PT runs fast graph-based analysis by default and can recover pessimism with path-based analysis (see GBA vs PBA).
- ECO flow, fix_eco_timing proposes fixes; write_changes hands them to place-and-route.
- Distributed multi-scenario, PT-DMSA runs many MMMC scenarios in parallel across a compute farm.
| Command | Purpose |
|---|---|
| read_verilog / link_design | Read and link the routed netlist |
| read_parasitics | Load SPEF parasitics from layout |
| read_sdc / set_propagated_clock | Constraints + real clock latencies |
| update_timing | Compute the timing graph |
| report_timing / report_constraint | Worst paths and violations |
| report_timing -pba_mode exhaustive | Path-based analysis (recover margin) |
In short, PrimeTime is signoff STA: read the netlist, SPEF and SDC, propagate the clock, update and report timing across every scenario, recover margin with PBA, and emit an ECO. Clean in PT across all corners and modes is what "timing signed off" means.