diff --git a/sdc-plugin/Makefile b/sdc-plugin/Makefile
index b4694ca..3089554 100644
--- a/sdc-plugin/Makefile
+++ b/sdc-plugin/Makefile
@@ -4,7 +4,7 @@
 LDLIBS = $(shell yosys-config --ldlibs)
 PLUGINS_DIR = $(shell yosys-config --datdir)/plugins
 
-OBJS = buffers.o clocks.o propagation.o sdc.o
+OBJS = buffers.o clocks.o propagation.o sdc.o sdc_writer.o set_false_path.o
 
 sdc.so: $(OBJS)
 	$(CXX) $(CXXFLAGS) $(LDFLAGS) -shared -o $@ $^ $(LDLIBS)
diff --git a/sdc-plugin/sdc_writer.cc b/sdc-plugin/sdc_writer.cc
new file mode 100644
index 0000000..daae7e2
--- /dev/null
+++ b/sdc-plugin/sdc_writer.cc
@@ -0,0 +1,63 @@
+/*
+ *  yosys -- Yosys Open SYnthesis Suite
+ *
+ *  Copyright (C) 2020  The Symbiflow Authors
+ *
+ *  Permission to use, copy, modify, and/or distribute this software for any
+ *  purpose with or without fee is hereby granted, provided that the above
+ *  copyright notice and this permission notice appear in all copies.
+ *
+ *  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ *  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ *  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ *  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ *  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ *  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ *  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+#include "sdc_writer.h"
+
+USING_YOSYS_NAMESPACE
+
+void SdcWriter::AddFalsePath(FalsePath false_path) {
+    false_paths_.push_back(false_path);
+}
+
+void SdcWriter::WriteSdc(Clocks& clocks, std::ostream& file) {
+    WriteClocks(clocks, file);
+    WriteFalsePaths(file);
+}
+
+void SdcWriter::WriteClocks(Clocks& clocks, std::ostream& file) {
+    for (auto clock : clocks.GetClocks()) {
+	auto clock_wires = clock.GetClockWires();
+	// FIXME: Input port nets are not found in VPR
+	if (std::all_of(clock_wires.begin(), clock_wires.end(),
+	                [&](RTLIL::Wire* wire) { return wire->port_input; })) {
+	    continue;
+	}
+	file << "create_clock -period " << clock.Period();
+	file << " -waveform {" << clock.RisingEdge() << " "
+	     << clock.FallingEdge() << "}";
+	for (auto clock_wire : clock_wires) {
+	    if (clock_wire->port_input) {
+		continue;
+	    }
+	    file << " " << Clock::ClockWireName(clock_wire);
+	}
+	file << std::endl;
+    }
+}
+
+void SdcWriter::WriteFalsePaths(std::ostream& file) {
+    for (auto path : false_paths_) {
+	file << "set_false_path";
+	if (!path.from_pin.empty()) {
+	    file << " -from " << path.from_pin;
+	}
+	if (!path.to_pin.empty()) {
+	    file << " -to " << path.to_pin;
+	}
+	file << std::endl;
+    }
+}
diff --git a/sdc-plugin/sdc_writer.h b/sdc-plugin/sdc_writer.h
new file mode 100644
index 0000000..f5f18b3
--- /dev/null
+++ b/sdc-plugin/sdc_writer.h
@@ -0,0 +1,41 @@
+/*
+ *  yosys -- Yosys Open SYnthesis Suite
+ *
+ *  Copyright (C) 2020  The Symbiflow Authors
+ *
+ *  Permission to use, copy, modify, and/or distribute this software for any
+ *  purpose with or without fee is hereby granted, provided that the above
+ *  copyright notice and this permission notice appear in all copies.
+ *
+ *  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ *  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ *  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ *  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ *  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ *  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ *  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+#ifndef _SDC_WRITER_H_
+#define _SDC_WRITER_H_
+#include "clocks.h"
+
+USING_YOSYS_NAMESPACE
+
+struct FalsePath {
+    std::string from_pin;
+    std::string to_pin;
+};
+
+class SdcWriter {
+   public:
+    void AddFalsePath(FalsePath false_path);
+    void WriteSdc(Clocks& clocks, std::ostream& file);
+
+   private:
+    void WriteClocks(Clocks& clocks, std::ostream& file);
+    void WriteFalsePaths(std::ostream& file);
+
+    std::vector<FalsePath> false_paths_;
+};
+
+#endif  // _SDC_WRITER_H_