Added full design created with Claude

examples/amaranth_cdc.py

@@ -0,0 +1,107 @@
+from amaranth import *
+from amaranth.sim import Simulator
+
+
+class SyncFF(Elaboratable):
+    """Width-N multi-flop synchronizer from `src_domain` to `dst_domain`.
+
+    Use when the source is a level signal that may be stable for multiple destination
+    cycles. Not suitable for single-cycle pulses (use TogglePulseSync instead).
+    """
+
+    def __init__(self, width=1, src_domain="src", dst_domain="dst"):
+        self.width = width
+        self.src_domain = src_domain
+        self.dst_domain = dst_domain
+        self.src = Signal(self.width)
+        self.dst = Signal(self.width)
+
+    def elaborate(self, platform):
+        m = Module()
+        reg_src = Signal(self.width)
+        ff0 = Signal(self.width)
+        ff1 = Signal(self.width)
+
+        m.d[self.src_domain] += reg_src.eq(self.src)
+        m.d[self.dst_domain] += ff0.eq(reg_src)
+        m.d[self.dst_domain] += ff1.eq(ff0)
+        m.d.comb += self.dst.eq(ff1)
+
+        return m
+
+
+class TogglePulseSync(Elaboratable):
+    """Reliable pulse transfer from `src_domain` into `dst_domain`.
+
+    - Source toggles `toggle` whenever an event occurs.
+    - Destination synchronizes the toggle and detects edges.
+    Guarantees ordering and no lost pulses for single-bit events.
+    """
+
+    def __init__(self, src_domain="src", dst_domain="dst"):
+        self.src_domain = src_domain
+        self.dst_domain = dst_domain
+        self.src_pulse = Signal()
+        self.dst_pulse = Signal()
+
+    def elaborate(self, platform):
+        m = Module()
+        toggle = Signal()
+        sync0 = Signal()
+        sync1 = Signal()
+        prev = Signal()
+        edge = Signal()
+
+        # Source domain: flip the toggle when a pulse arrives
+        m.d[self.src_domain] += If(self.src_pulse, toggle.eq(~toggle))
+
+        # Destination domain: two-flop synchronize the toggle
+        m.d[self.dst_domain] += sync0.eq(toggle)
+        m.d[self.dst_domain] += sync1.eq(sync0)
+
+        # Detect the change in the destination domain
+        m.d[self.dst_domain] += edge.eq(sync1 ^ prev)
+        m.d[self.dst_domain] += prev.eq(sync1)
+        m.d.comb += self.dst_pulse.eq(edge)
+
+        return m
+
+
+def _sim_toggle_pulse():
+    """Simple simulation that drives pulses on the source domain and prints detections on the destination domain."""
+
+    top = Module()
+    t = TogglePulseSync(src_domain="src", dst_domain="dst")
+    top.submodules.t = t
+
+    sim = Simulator(top)
+    # Create two asynchronous clocks (periods chosen arbitrarily for the sim)
+    sim.add_clock(1e-6, domain="src")
+    sim.add_clock(1.5e-6, domain="dst")
+
+    def process():
+        # Wait a little, then generate three source pulses at different phases
+        for _ in range(5):
+            yield
+
+        for i in range(3):
+            yield t.src_pulse.eq(1)
+            yield
+            yield t.src_pulse.eq(0)
+            # let the domains run for a few cycles
+            for _ in range(10):
+                dp = (yield t.dst_pulse)
+                if dp:
+                    print(f"dst detected pulse at sim tick")
+                yield
+
+        # run a bit longer to observe behavior
+        for _ in range(20):
+            yield
+
+    sim.add_sync_process(process, domain="src")
+    sim.run_until(100e-6)
+
+
+if __name__ == "__main__":
+    _sim_toggle_pulse()