diff --git a/power_fv/__init__.py b/power_fv/__init__.py
index 45b5fd1..b55b1ca 100644
--- a/power_fv/__init__.py
+++ b/power_fv/__init__.py
@@ -1,2 +1,10 @@
 from importlib import metadata
 __version__ = metadata.version(__package__)
+
+
+from .dut import *
+
+
+__all__ = [
+    "Interface",
+]
diff --git a/power_fv/dut.py b/power_fv/dut.py
new file mode 100644
index 0000000..ba071ce
--- /dev/null
+++ b/power_fv/dut.py
@@ -0,0 +1,22 @@
+from amaranth import *
+
+
+__all__ = ["Interface"]
+
+
+class Interface(Record):
+    """POWER-FV interface.
+
+    The interface between the formal testbench and the processor-under-test.
+
+    Attributes
+    ----------
+    stb : Signal
+        Instruction strobe. Asserted when the processor retires an instruction. Other signals are
+        only valid when ``stb`` is asserted.
+    """
+    def __init__(self, *, name=None, src_loc_at=0):
+        layout = [
+            ("stb", 1),
+        ]
+        super().__init__(layout, name=name, src_loc_at=1 + src_loc_at)