diff --git a/artiq/gateware/test/rtio/test_fastlink.py b/artiq/gateware/test/rtio/test_fastlink.py
index 5b62c9aba..4304963d6 100644
--- a/artiq/gateware/test/rtio/test_fastlink.py
+++ b/artiq/gateware/test/rtio/test_fastlink.py
@@ -23,12 +23,13 @@ class TestPhaser(unittest.TestCase):
             clk = (clk << 2) & 0xff
             clk |= (yield self.dut.data[0])
             if clk == 0x0f:
-                marker = (marker << 1) & 0x7f
-                marker |= (yield self.dut.data[1]) & 1
-                if marker >> 1 == 0x01:
+                if marker == 0x01:
                     stb += 1
                     if stb >= 3:
                         break
+                # 10/2 + 1 marker bits
+                marker = (marker << 1) & 0x3f
+                marker |= (yield self.dut.data[1]) & 1
             yield
 
     def test_frame(self):
@@ -41,3 +42,45 @@ class TestPhaser(unittest.TestCase):
         self.assertEqual([d[0] for d in frame], [0, 0, 3, 3] * 10)
         self.assertEqual([d[1] & 1 for d in frame[4*4 - 1:10*4 - 1:4]],
                          [0, 0, 0, 0, 0, 1])
+
+
+class TestFastino(unittest.TestCase):
+    def setUp(self):
+        self.dut = SerDes(
+            n_data=8, t_clk=7, d_clk=0b1100011,
+            n_frame=14, n_crc=12, poly=0x80f)
+
+    def test_init(self):
+        pass
+
+    def record_frame(self, frame):
+        clk = 0
+        marker = 0
+        stb = 0
+        while True:
+            if stb == 2:
+                frame.append((yield self.dut.data))
+            clk = (clk << 2) & 0xff
+            clk |= (yield self.dut.data[0])
+            if clk in (0b11100011, 0b11000111):
+                if marker == 0x01:
+                    stb += 1
+                    if stb >= 3:
+                        break
+                # 14/2 + 1 marker bits
+                marker = (marker << 1) & 0xff
+                if clk & 0b100:
+                    marker |= (yield self.dut.data[1]) >> 1
+                else:
+                    marker |= (yield self.dut.data[1]) & 1
+            yield
+
+    def test_frame(self):
+        frame = []
+        self.dut.comb += self.dut.payload.eq((1 << len(self.dut.payload)) - 1)
+        run_simulation(self.dut, self.record_frame(frame),
+            clocks={n: 2 for n in ["sys", "rio", "rio_phy"]},
+            vcd_name="fastlink.vcd")
+        self.assertEqual(len(frame), 7*14//2)
+        self.assertEqual([d[0] for d in frame], [3, 0, 1, 3, 2, 0, 3] * 7)
+        print(frame)