diff --git a/examples/zynq7000/SIM/tb_heartbeat.vhd b/examples/zynq7000/SIM/tb_heartbeat.vhd
new file mode 100644
index 0000000..82b10b2
--- /dev/null
+++ b/examples/zynq7000/SIM/tb_heartbeat.vhd
@@ -0,0 +1,44 @@
+library IEEE;
+use IEEE.STD_LOGIC_1164.all;
+use IEEE.NUMERIC_STD.all;
+
+entity tb_heartbeat is
+end entity;
+
+architecture behavioural of tb_heartbeat is
+    -- COMPONENTS
+    -- ----------
+    component heartbeat is
+        generic (
+            Fin  : integer := 100000000;
+            Fout : integer := 8
+        );
+        port (
+            ACLK    : in std_logic;
+            ARESETN : in std_logic;
+            LED     : out std_logic_vector(1 downto 0)
+        );
+    end component;
+    -- SIGNALS
+    -- -------
+    signal ACLK : std_logic := '0';
+    signal LED : std_logic_vector(1 downto 0) := "00";
+    signal ARESETN : std_logic := '0';
+begin
+    c_heartbeat : component heartbeat generic map(
+        50000000,
+        5000000
+        ) port map(
+        ACLK    => ACLK,
+        ARESETN => ARESETN,
+        LED     => LED
+    );
+    ACLK <= not ACLK after 10 ns;
+    ARESETN <= '1' after 150 ns;
+
+    process
+    begin
+        wait for 5000 ns;
+        report "END OF SIMULATION" severity failure;
+    end process;
+end architecture;
\ No newline at end of file
diff --git a/examples/zynq7000/project.cfg b/examples/zynq7000/project.cfg
index c7e19fa..bf674e6 100644
--- a/examples/zynq7000/project.cfg
+++ b/examples/zynq7000/project.cfg
@@ -39,7 +39,7 @@ package             = clg400
 speedgrade          = -2
 toplevel            = toplevel
 # Created netlist toplevel
-netlist_top         = toplevel
+netlist_top         = toplevel.heartbeat_i
 synth_opts          = -flatten_hierarchy none -keep_equivalent_registers
 #opt_opts           =
 #place_opts         =
@@ -51,4 +51,23 @@ files_vhdl          = RTL/heartbeat.vhd RTL/toplevel.vhd
 #files_sysverilog   =
 files_con           = CON/toplevel.xdc
 files_xci           = OUT/ip/rst_gen/rst_gen.xci OUT/ip/zynqps/zynqps.xci
+# ######################################
+
+# ######################################
+# Behavioural simulation
+[target.sim]
+toolchain           = xsim
+
+# Toolchain settings
+toplevel            = tb_heartbeat
+vcdlevels           = 20
+runtime             = all
+#xelab_opts         = 
+
+# Fileset
+files_vhdl          = RTL/heartbeat.vhd
+                      SIM/tb_heartbeat.vhd
+#files_verilog      =
+#files_sysverilog   =
+#files_xci          = 
 # ######################################
\ No newline at end of file
diff --git a/remotesyn/toolchains/isim.py b/remotesyn/toolchains/isim.py
index 1509138..94ab41c 100644
--- a/remotesyn/toolchains/isim.py
+++ b/remotesyn/toolchains/isim.py
@@ -4,6 +4,10 @@ import time
 import subprocess
 
 def do(config, target, log, subprocesses, prefix='.'):
+    shutil.rmtree(config.get('project', 'build_dir', fallback='build'), True)
+
+    log("Starting simulation")
+    
     log(" - parsing options")
     toplevel = config.get(f'target.{target}', 'toplevel', fallback='toplevel')
     vcdlevels = config.get(f'target.{target}', 'vcdlevels', fallback='1')
diff --git a/remotesyn/toolchains/xsim.py b/remotesyn/toolchains/xsim.py
new file mode 100644
index 0000000..56e71ad
--- /dev/null
+++ b/remotesyn/toolchains/xsim.py
@@ -0,0 +1,154 @@
+import shutil
+import os
+import time
+import subprocess
+
+def do(config, target, log, subprocesses, prefix='.'):
+    shutil.rmtree(config.get('project', 'build_dir', fallback='build'), True)
+
+    log("Starting simulation")
+
+    log(" - parsing options")
+    device = config.get(f'target.{target}', 'device', fallback='')
+    package = config.get(f'target.{target}', 'package', fallback='')
+    speedgrade = config.get(f'target.{target}', 'speedgrade', fallback='')
+    toplevel = config.get(f'target.{target}', 'toplevel', fallback='toplevel')
+    runtime = config.get(f'target.{target}', 'runtime', fallback='100 ns')
+    xelab_opts = config.get(f'target.{target}', 'xelab_opts', fallback='')
+    files_vhdl = config.get(f'target.{target}', 'files_vhdl', fallback='').split()
+    files_verilog = config.get(f'target.{target}', 'files_verilog', fallback='').split()
+    files_sysverilog = config.get(f'target.{target}', 'files_sysverilog', fallback='').split()
+    files_xci = config.get(f'target.{target}', 'files_xci', fallback='').split()
+    build_dir = config.get(f'project', 'build_dir', fallback='build')
+    out_dir = config.get(f'project', 'out_dir', fallback='out')
+
+    prefix = f'{os.getcwd()}/{prefix}'
+    build_dir = f'{prefix}/{build_dir}'
+    out_dir = f'{prefix}/{out_dir}/{target}'
+
+    log(" - creating output directories")
+    os.makedirs(build_dir, exist_ok=True)
+    os.makedirs(out_dir, exist_ok=True)
+
+    log(" - writing project tcl file")
+    with open(f'{build_dir}/do.tcl', 'w') as f:
+        f.write('set_param general.maxThreads 8\n')
+        f.write(f'create_project -force sim sim\n')
+        for s in files_vhdl:
+            f.write(f"add_files -norecurse -scan_for_includes \"{prefix}/{s}\"\n")
+            f.write(f"import_files -norecurse \"{prefix}/{s}\"\n")
+        for s in files_verilog:
+            f.write(f"add_files -norecurse -scan_for_includes \"{prefix}/{s}\"\n")
+            f.write(f"import_files -norecurse \"{prefix}/{s}\"\n")
+        for s in files_sysverilog:
+            f.write(f"add_files -norecurse -scan_for_includes \"{prefix}/{s}\"\n")
+            f.write(f"import_files -norecurse \"{prefix}/{s}\"\n")
+        for s in files_xci:
+            f.write(f"add_files -norecurse -scan_for_includes \"{prefix}/{s}\"\n")
+        # TODO C files for VPI
+
+        f.write(f"set_property top {toplevel} [get_filesets sim_1]\n")
+        f.write("set_property top_lib xil_defaultlib [get_filesets sim_1]\n")
+        f.write("launch_simulation -noclean_dir -scripts_only -absolute_path\n")
+
+    log(" - run vivado")
+
+    p = subprocess.Popen(f"vivado -mode batch -source do.tcl", 
+        shell=True, cwd=build_dir, 
+        stdin=subprocess.DEVNULL, stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL)
+    subprocesses.append(p)
+    while p.poll() is None:
+        time.sleep(1)
+    res = p.returncode
+
+    log(" - copy logs")
+    shutil.copy(f'{build_dir}/vivado.log', f'{out_dir}/synth.log')
+
+    if res!=0:
+        return res
+
+    log(" - patch run scripts")
+
+    p = subprocess.Popen(f'sed -i "s/xelab/xelab {xelab_opts}/g" elaborate.sh', 
+        shell=True, cwd=f'{build_dir}/sim/sim.sim/sim_1/behav/xsim', 
+        stdin=subprocess.DEVNULL, stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL)
+    subprocesses.append(p)
+    while p.poll() is None:
+        time.sleep(1)
+    res = p.returncode
+
+    if res!=0:
+        return res
+
+    # needed for postsim?
+    # p = subprocess.Popen(f"sed -i '/ \/I /d' netlist.sdf >> {build_dir}/patch.log && sed -i '/glbl.v/d' *.prj >> {build_dir}/patch.log", 
+    #     shell=True, cwd=f'{build_dir}/sim/sim.sim/sim_1/behav/xsim', 
+    #     stdin=subprocess.DEVNULL, stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL)
+    # subprocesses.append(p)
+    # while p.poll() is None:
+    #     time.sleep(1)
+    # res = p.returncode
+
+    # log(" - copy logs")
+    # shutil.copy(f'{build_dir}/patch.log', f'{out_dir}/patch.log')
+
+    # if res!=0:
+    #     return res
+
+    log(" - compile")
+
+    p = subprocess.Popen(f'bash compile.sh', 
+        shell=True, cwd=f'{build_dir}/sim/sim.sim/sim_1/behav/xsim', 
+        stdin=subprocess.DEVNULL, stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL)
+    subprocesses.append(p)
+    while p.poll() is None:
+        time.sleep(1)
+    res = p.returncode
+
+    log(" - copy logs")
+    shutil.copy(f'{build_dir}/sim/sim.sim/sim_1/behav/xsim/compile.log', f'{out_dir}/compile.log')
+
+    if res!=0:
+        return res
+
+    log(" - elaborate")
+
+    p = subprocess.Popen(f'bash elaborate.sh', 
+        shell=True, cwd=f'{build_dir}/sim/sim.sim/sim_1/behav/xsim', 
+        stdin=subprocess.DEVNULL, stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL)
+    subprocesses.append(p)
+    while p.poll() is None:
+        time.sleep(1)
+    res = p.returncode
+
+    log(" - copy logs")
+    shutil.copy(f'{build_dir}/sim/sim.sim/sim_1/behav/xsim/elaborate.log', f'{out_dir}/elaborate.log')
+
+    if res!=0:
+        return res
+
+    log(" - write simulation script")
+    with open(f'{build_dir}/sim/sim.sim/sim_1/behav/xsim/{toplevel}.tcl', 'w') as f:
+        f.write(f"open_vcd out.vcd\nlog_vcd\nrun {runtime}\nclose_vcd\nquit\n")
+
+    log(" - simulate")
+
+    p = subprocess.Popen(f'bash simulate.sh', 
+        shell=True, cwd=f'{build_dir}/sim/sim.sim/sim_1/behav/xsim', 
+        stdin=subprocess.DEVNULL, stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL)
+    subprocesses.append(p)
+    while p.poll() is None:
+        time.sleep(1)
+    res = p.returncode
+
+    log(" - copy logs")
+    shutil.copy(f'{build_dir}/sim/sim.sim/sim_1/behav/xsim/simulate.log', f'{out_dir}/simulate.log')
+
+    if res!=0:
+        return res
+
+    log(" - copy output files")
+    shutil.copy(f'{build_dir}/sim/sim.sim/sim_1/behav/xsim/out.vcd', f'{out_dir}/out.vcd')
+
+    return res
+