133 lines
4.5 KiB
C++
133 lines
4.5 KiB
C++
// OpenSTA, Static Timing Analyzer
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// Copyright (c) 2023, Parallax Software, Inc.
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//
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// This program is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program. If not, see <https://www.gnu.org/licenses/>.
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#include "DelayCalcBase.hh"
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#include "Liberty.hh"
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#include "TimingArc.hh"
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#include "Network.hh"
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#include "Parasitics.hh"
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namespace sta {
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DelayCalcBase::DelayCalcBase(StaState *sta) :
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ArcDelayCalc(sta)
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{
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}
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void
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DelayCalcBase::finishDrvrPin()
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{
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for (auto parasitic : unsaved_parasitics_)
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parasitics_->deleteUnsavedParasitic(parasitic);
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unsaved_parasitics_.clear();
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for (auto drvr_pin : reduced_parasitic_drvrs_)
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parasitics_->deleteDrvrReducedParasitics(drvr_pin);
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reduced_parasitic_drvrs_.clear();
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}
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void
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DelayCalcBase::inputPortDelay(const Pin *,
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float in_slew,
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const RiseFall *rf,
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const Parasitic *parasitic,
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const DcalcAnalysisPt *)
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{
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drvr_cell_ = nullptr;
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drvr_library_ = network_->defaultLibertyLibrary();
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drvr_slew_ = in_slew;
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drvr_rf_ = rf;
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drvr_parasitic_ = parasitic;
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input_port_ = true;
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}
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void
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DelayCalcBase::gateDelayInit(const TimingArc *arc,
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const Slew &in_slew,
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const Parasitic *drvr_parasitic)
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{
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drvr_cell_ = arc->from()->libertyCell();
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drvr_library_ = drvr_cell_->libertyLibrary();
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drvr_rf_ = arc->toEdge()->asRiseFall();
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drvr_slew_ = in_slew;
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drvr_parasitic_ = drvr_parasitic;
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input_port_ = false;
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}
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// For DSPF on an input port the elmore delay is used as the time
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// constant of an exponential waveform. The delay to the logic
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// threshold and slew are computed for the exponential waveform.
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// Note that this uses the driver thresholds and relies on
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// thresholdAdjust to convert the delay and slew to the load's thresholds.
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void
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DelayCalcBase::dspfWireDelaySlew(const Pin *,
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float elmore,
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ArcDelay &wire_delay,
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Slew &load_slew)
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{
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float vth = drvr_library_->inputThreshold(drvr_rf_);
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float vl = drvr_library_->slewLowerThreshold(drvr_rf_);
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float vh = drvr_library_->slewUpperThreshold(drvr_rf_);
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float slew_derate = drvr_library_->slewDerateFromLibrary();
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wire_delay = -elmore * log(1.0 - vth);
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load_slew = drvr_slew_ + elmore * log((1.0 - vl) / (1.0 - vh)) / slew_derate;
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}
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void
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DelayCalcBase::thresholdAdjust(const Pin *load_pin,
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ArcDelay &load_delay,
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Slew &load_slew)
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{
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LibertyLibrary *load_library = thresholdLibrary(load_pin);
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if (load_library
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&& drvr_library_
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&& load_library != drvr_library_) {
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float drvr_vth = drvr_library_->outputThreshold(drvr_rf_);
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float load_vth = load_library->inputThreshold(drvr_rf_);
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float drvr_slew_delta = drvr_library_->slewUpperThreshold(drvr_rf_)
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- drvr_library_->slewLowerThreshold(drvr_rf_);
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float load_delay_delta =
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delayAsFloat(load_slew) * ((load_vth - drvr_vth) / drvr_slew_delta);
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load_delay += (drvr_rf_ == RiseFall::rise())
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? load_delay_delta
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: -load_delay_delta;
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float load_slew_delta = load_library->slewUpperThreshold(drvr_rf_)
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- load_library->slewLowerThreshold(drvr_rf_);
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float drvr_slew_derate = drvr_library_->slewDerateFromLibrary();
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float load_slew_derate = load_library->slewDerateFromLibrary();
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load_slew = load_slew * ((load_slew_delta / load_slew_derate)
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/ (drvr_slew_delta / drvr_slew_derate));
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}
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}
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LibertyLibrary *
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DelayCalcBase::thresholdLibrary(const Pin *load_pin)
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{
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if (network_->isTopLevelPort(load_pin))
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// Input/output slews use the default (first read) library
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// for slew thresholds.
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return network_->defaultLibertyLibrary();
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else {
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LibertyPort *lib_port = network_->libertyPort(load_pin);
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if (lib_port)
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return lib_port->libertyCell()->libertyLibrary();
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else
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return network_->defaultLibertyLibrary();
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}
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}
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} // namespace
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