write_path_spice

Signed-off-by: James Cherry <cherry@parallaxsw.com>

search/WritePathSpice.cc

@@ -170,6 +170,8 @@ private:
   float slewAxisMinValue(TimingArc *arc);
   float pgPortVoltage(LibertyPgPort *pg_port);
   void writePrintStmt();
+  float railToRailSlew(float slew,
+                       const RiseFall *rf);
 
   // Stage "accessors".
   //
@@ -408,11 +410,21 @@ WritePathSpice::maxTime()
   else {
     float end_slew = findSlew(path_);
     float arrival = delayAsFloat(path_->arrival(this));
-    float max_time = input_slew + arrival + end_slew;
+    float max_time = railToRailSlew(input_slew, rf) + arrival
+      + railToRailSlew(end_slew, rf);
     return max_time;
   }
 }
 
+float
+WritePathSpice::railToRailSlew(float slew,
+                               const RiseFall *rf)
+{
+  float lower = default_library_->slewLowerThreshold(rf);
+  float upper = default_library_->slewUpperThreshold(rf);
+  return slew / (upper - lower);
+}
+
 void
 WritePathSpice::writeStageInstances()
 {
@@ -492,8 +504,11 @@ WritePathSpice::writeInputWaveform()
   const RiseFall *rf = input_path->transition(this);
   TimingArc *next_arc = stageGateArc(input_stage + 1);
   float slew0 = findSlew(input_path, rf, next_arc);
-  // Arbitrary offset.
+
-  float time0 = slew0;
+  float threshold = default_library_->inputThreshold(rf);
+  float dt = railToRailSlew(slew0, rf);
+  float time0 = dt * threshold;
+
   int volt_index = 1;
   const Pin *drvr_pin = stageDrvrPin(input_stage);
   const Pin *load_pin = stageLoadPin(input_stage);
@@ -689,12 +704,11 @@ WritePathSpice::writeWaveformEdge(const RiseFall *rf,
     volt1 = gnd_voltage_;
   }
   float threshold = default_library_->inputThreshold(rf);
-  float lower = default_library_->slewLowerThreshold(rf);
+  float dt = railToRailSlew(slew, rf);
-  float upper = default_library_->slewUpperThreshold(rf);
-  float dt = slew / (upper - lower);
   float time0 = time - dt * threshold;
   float time1 = time0 + dt;
-  streamPrint(spice_stream_, "+%.3e %.3e\n", time0, volt0);
+  if (time0 > 0.0)
+    streamPrint(spice_stream_, "+%.3e %.3e\n", time0, volt0);
   streamPrint(spice_stream_, "+%.3e %.3e\n", time1, volt1);
 }
 

tcl/Search.tcl

@@ -249,7 +249,7 @@ proc report_delays_wrt_clk { vertex what clk clk_rf } {
     set rise_fmt [format_delays $rise]
     set fall_fmt [format_delays $fall]
     if {$clk != "NULL"} {
-      set clk_str " ([get_name $clk] [rise_fall_short_name $clk_rf])"
+      set clk_str " ([get_name $clk] [rf_short_name $clk_rf])"
     } else {
       set clk_str ""
     }
@@ -281,7 +281,7 @@ proc report_wrt_clk { vertex what clk clk_rf } {
     set rise_fmt [format_times $rise $sta_report_default_digits]
     set fall_fmt [format_times $fall $sta_report_default_digits]
     if {$clk != "NULL"} {
-      set clk_str " ([get_name $clk] [rise_fall_short_name $clk_rf])"
+      set clk_str " ([get_name $clk] [rf_short_name $clk_rf])"
     } else {
       set clk_str ""
     }
@@ -289,16 +289,6 @@ proc report_wrt_clk { vertex what clk clk_rf } {
   }
 }
 
-proc rise_fall_short_name { rf } {
-  if { $rf == "rise" } {
-    return [rise_short_name]
-  } elseif { $rf == "fall" } {
-    return [fall_short_name]
-  } else {
-    error "unknown transition name $rf"
-  }
-}
-
 proc times_are_inf { times } {
   foreach time $times {
     if { $time < 1e+10 && $time > -1e+10 } {
@@ -1164,6 +1154,16 @@ proc max_fanout_check_slack_limit {} {
 
 ################################################################
 
+proc rf_short_name { rf } {
+  if { [rf_is_rise $rf] } {
+    return [rise_short_name]
+  } elseif { [rf_is_fall $rf] } {
+    return [fall_short_name]
+  } else {
+    error "unknown transition name $rf"
+  }
+}
+
 proc opposite_rf { rf } {
   if { [rf_is_rise $rf] } {
     return "fall"