diff --git a/artiq/coredevice/phaser.py b/artiq/coredevice/phaser.py
new file mode 100644
index 000000000..9ebd86d74
--- /dev/null
+++ b/artiq/coredevice/phaser.py
@@ -0,0 +1,45 @@
+from artiq.language.core import kernel, portable, delay
+from artiq.coredevice.rtio import rtio_output, rtio_input_data
+from artiq.language.units import us
+from artiq.language.types import TInt32, TList, TFloat
+
+
+PHASER_ADDR_BOARD_ID = 0x00
+PHASER_BOARD_ID = 19
+
+class Phaser:
+    kernel_invariants = {"core", "channel_base"}
+
+    def __init__(self, dmgr, channel_base, readback_delay=1,
+                 core_device="core"):
+        self.channel_base = channel_base << 8
+        self.core = dmgr.get(core_device)
+        self.readback_delay = readback_delay
+
+    @kernel
+    def init(self):
+        board_id = self.read(PHASER_ADDR_BOARD_ID)
+        if board_id != PHASER_BOARD_ID:
+            raise ValueError("invalid board id")
+
+    @kernel
+    def write(self, addr, data):
+        """Write data to a Fastino register.
+
+        :param addr: Address to write to.
+        :param data: Data to write.
+        """
+        rtio_output(self.channel_base | addr | 0x80, data)
+
+    @kernel
+    def read(self, addr):
+        """Read from Fastino register.
+
+        TODO: untested
+
+        :param addr: Address to read from.
+        :return: The data read.
+        """
+        rtio_output(self.channel_base | addr, 0)
+        response = rtio_input_data(self.channel_base >> 8)
+        return response >> self.readback_delay
diff --git a/artiq/frontend/artiq_ddb_template.py b/artiq/frontend/artiq_ddb_template.py
index 86452c607..8a3122f9b 100755
--- a/artiq/frontend/artiq_ddb_template.py
+++ b/artiq/frontend/artiq_ddb_template.py
@@ -491,7 +491,10 @@ class PeripheralManager:
                 "type": "local",
                 "module": "artiq.coredevice.phaser",
                 "class": "Phaser",
-                "arguments": {{"channel": 0x{channel:06x}}}
+                "arguments": {{
+                    "channel_base": 0x{channel:06x},
+                    "readback_delay": 1,
+                }}
             }}""",
             name=self.get_name("phaser"),
             channel=rtio_offset)
diff --git a/artiq/gateware/rtio/phy/fastlink.py b/artiq/gateware/rtio/phy/fastlink.py
index a7003c15e..0c361b901 100644
--- a/artiq/gateware/rtio/phy/fastlink.py
+++ b/artiq/gateware/rtio/phy/fastlink.py
@@ -86,6 +86,9 @@ class SerDes(Module):
             self.crcb.data.eq(Cat([sri[-2] for sri in sr[::-1]])),
             self.crcb.last.eq(self.crca.next),
             miso_sr_next.eq(Cat(self.data[-1], miso_sr)),
+            # unload miso
+            self.readback.eq(Cat([miso_sr_next[t_miso + i*t_clk]
+                                  for i in range(n_frame)])),
         ]
         self.sync.rio_phy += [
             # shift everything by two bits
@@ -101,9 +104,6 @@ class SerDes(Module):
                 self.crca.last.eq(0),
                 # transpose, load
                 [sri.eq(Cat(words[i::n_mosi])) for i, sri in enumerate(sr)],
-                # unload miso
-                self.readback.eq(Cat([miso_sr_next[t_miso + i*t_clk]
-                                      for i in range(n_frame)])),
                 # inject crc for the last cycle
                 crc_insert.eq(self.crca.next if n_crc // n_mosi == 1
                               else self.crcb.next),
diff --git a/artiq/gateware/rtio/phy/phaser.py b/artiq/gateware/rtio/phy/phaser.py
index f50ba111b..19390f51d 100644
--- a/artiq/gateware/rtio/phy/phaser.py
+++ b/artiq/gateware/rtio/phy/phaser.py
@@ -32,8 +32,7 @@ class Phaser(Module):
         n_channels = 2
         n_samples = 8
         n_bits = 14
-        body = [[(Signal(n_bits), Signal(n_bits))
-                 for i in range(n_channels)] for j in range(n_samples)]
+        body = [Signal(n_bits) for i in range(n_channels*n_samples*2)]
         assert len(Cat(header.raw_bits(), body)) == \
                 len(self.serializer.payload)
         self.comb += self.serializer.payload.eq(Cat(header.raw_bits(), body))