diff --git a/dg645Sup/Makefile b/dg645Sup/Makefile
index ca08d77..e1cf4a7 100644
--- a/dg645Sup/Makefile
+++ b/dg645Sup/Makefile
@@ -8,6 +8,7 @@ DB += dg645_logic.db
 DB += dg645_delay.db
 DB += dg645_width.db
 DB += dg645_delay_width_shared.db
+DB += litron.db
 
 #=======================================
 include $(TOP)/configure/RULES
diff --git a/dg645Sup/litron.db b/dg645Sup/litron.db
new file mode 100644
index 0000000..14b7408
--- /dev/null
+++ b/dg645Sup/litron.db
@@ -0,0 +1,144 @@
+record(calc, "$(P)$(R)$(chan1=A)DLAYSCAL")
+{
+    field(DESC, "Scaled raw value of ADELAY")
+    field(INPA, "$(P)$(R)$(chan1=A)DelayAI CP MS") # This is raw value scaled to 'us'
+    field(INPB, "1e6")
+    field(CALC, "A*B")
+    field(EGU, "us")
+}
+
+record(calc, "$(P)$(R)$(chan2=C)DLAYSCAL")
+{
+    field(DESC, "Scaled raw value of CDELAY")
+    field(INPA, "$(P)$(R)$(chan2=C)DelayAI CP MS")
+    field(INPB, "1e6")
+    field(CALC, "A*B")
+    field(EGU, "us")
+}
+
+record(calc, "$(P)$(R)SUMMED_DELAY")
+{
+    field(DESC, "Add dA & dC")
+    field(INPA, "$(P)$(R)$(chan1=A)DLAYSCAL CP MS")
+    field(INPB, "$(P)$(R)$(chan2=C)DLAYSCAL CP MS")
+    field(CALC, "A+B") # Add ADELAY & CDELAY
+    field(EGU, "us")
+}
+
+record(ai, "$(P)$(R)OFFSET")
+{
+    field(DESC, "User Offset")
+    field(VAL, "0")
+    field(EGU, "us")
+}
+
+record(ai, "$(P)$(R)DELAY")
+{
+    field(DESC, "User Delay")
+    field(VAL, "0")
+    field(EGU, "us")
+}
+
+record(calc, "$(P)$(R)SUMMED_VALUE")
+{
+    field(DESC, "Add Delay Offset")
+    field(INPA, "$(P)$(R)DELAY CP")
+    field(INPB, "$(P)$(R)OFFSET CP")
+    field(CALC, "A+B") # Add DELAY & OFFSET
+    field(EGU, "us")
+}
+
+record(mbbo, "$(P)$(R)MODE")
+{
+    field(DESC, "Device Mode. auto|1|2")
+    field(ZRST, "auto")
+    field(ONST, "1")
+    field(TWST, "2")
+    field(FLNK, "$(P)$(R)_MODEAUTOCHECK") # When mode changes then check if in mode auto
+    field(PINI, "YES")
+    field(VAL, "0")
+}
+
+record(calcout, "$(P)$(R)_MODEAUTOCHECK")
+{
+    field(DESC, "Mode Auto Error Check")
+    field(INPA, "$(P)$(R)MODE")
+    field(INPB, "$(P)$(R)DELAY")
+    field(INPC, "$(P)$(R)OFFSET")
+    field(CALC, "A=1?A:(A=2?A:(B>ABS(C)?1:2))")
+    # If mode is 1 or 2 then return 1 or 2
+    # Else if DELAY > OFFSET return 1 else 2
+    field(OUT, "$(P)$(R)SET_MODE PP")
+}
+
+record(longout, "$(P)$(R)SET_MODE") # Send command to device to load settings from specified slot
+{
+    field(DESC, "Load Settings from slot 0(default) - 9")
+    field(EGU, "")
+    field(DTYP, "asynInt32")
+    field(OUT, "@asyn($(PORT)) RECALL") # *RCL
+}
+
+record(calc, "$(P)$(R)_MODE1CHECK")
+{
+    field(DESC, "Mode 1 Error Check")
+    field(INPA, "$(P)$(R)$(chan2=C)DLAYSCAL CP")
+    field(INPB, "$(P)$(R)SUMMED_VALUE CP")
+    field(CALC, "(A+B)>39900||B<0")
+    # If delay + summed_val bigger than 39900 or summed_val less than 0 then error
+}
+
+record(calc, "$(P)$(R)_MODE2CHECK")
+{
+    field(DESC, "Mode 2 Error Check")
+    field(INPA, "$(P)$(R)$(chan2=C)DLAYSCAL CP")
+    field(INPB, "$(P)$(R)SUMMED_VALUE CP")
+    field(CALC, "B>39900||(A+B)<=0")
+    # If delay + summed_val less than or equal to 0 or summed_val bigger than 39900 then error
+}
+
+record(calc, "$(P)$(R)_BOTHCHECKS")
+{
+    field(DESC, "Mode 1 & 2 Error Check")
+    field(INPA, "$(P)$(R)SET_MODE CP")
+    field(INPB, "$(P)$(R)_MODE1CHECK CP")
+    field(INPC, "$(P)$(R)_MODE2CHECK CP")
+    field(CALC, "(A=1)?B:C")
+    # If mode is 1 return _MODE1CHECK else _MODE2CHECK
+}
+
+record(calcout, "$(P)$(R)ERROR")
+{
+    field(DESC, "Check Modes")
+    field(INPA, "$(P)$(R)SET_MODE CP")
+    field(INPB, "$(P)$(R)_BOTHCHECKS")
+    field(CALC, "A=0||B") # If no error then write delay when set
+    field(OOPT, "When Zero")
+    field(OUT, "$(P)$(R)_WRITE_DELAY PP")
+    field(DOPT, "Use OCAL")
+    field(OCAL, "1")
+}
+
+record(seq, "$(P)$(R)_WRITE_DELAY")
+{
+    field(DESC, "Update Delay")
+    field(VAL, "0")
+
+    # 1) Units set
+    field(LNK1, "$(P)$(R)$(chan1=A)DELAYUNIT:SP")
+    field(DO1, "2")
+    # 2) Set t0
+    field(LNK2, "$(P)$(R)$(chan1=A)REFERENCE:SP")
+    field(DO2, "0")
+    # 3) Set delay A
+    field(LNK3, "$(P)$(R)$(chan1=A)DelayWriteAO")
+    field(DOL3, "$(P)$(R)SUMMED_VALUE")
+    # 4) Send
+    field(LNK4, "$(P)$(R)$(chan1=A)DELAYBUTTON")
+    field(DO4, "1")
+    # 5) *CLS (StatusClearBO)
+    field(LNK5, "$(P)$(R)StatusClearBO")
+    field(DO5, "1")
+    
+    field(SELM, "All")
+}
diff --git a/system_tests/lewis_emulators/Dg645/interfaces/stream_interface.py b/system_tests/lewis_emulators/Dg645/interfaces/stream_interface.py
index b0bf9f8..d150bfb 100644
--- a/system_tests/lewis_emulators/Dg645/interfaces/stream_interface.py
+++ b/system_tests/lewis_emulators/Dg645/interfaces/stream_interface.py
@@ -65,7 +65,12 @@ class Dg645StreamInterface(StreamInterface):
         # Commands below are only defined but not implemented because without it, the Delaygen
         # ASYN driver would crash
         CmdBuilder("get_prescale_factor").escape("PRES?").spaces().int().eos().build(),
-        CmdBuilder("get_prescale_phase_factor").escape("PHAS?").spaces().int().eos().build(),
+        CmdBuilder("get_prescale_phase_factor")
+        .escape("PHAS?")
+        .spaces()
+        .int()
+        .eos()
+        .build(),
         CmdBuilder("get_interface_config").escape("IFCF?").spaces().int().eos().build(),
         CmdBuilder("get_trigger_rate").escape("TRAT?").eos().build(),
         CmdBuilder("get_advanced_triggering_mode").escape("ADVT?").eos().build(),
diff --git a/system_tests/tests/dg645.py b/system_tests/tests/dg645.py
index e8f5f01..d78c841 100644
--- a/system_tests/tests/dg645.py
+++ b/system_tests/tests/dg645.py
@@ -1,3 +1,4 @@
+# pyright: reportMissingImports=false
 import unittest
 
 from parameterized import parameterized
@@ -89,19 +90,29 @@ def test_WHEN_logic_button_pressed_THEN_correct_logic_set_NR(self, _, channel):
         self.ca.assert_that_pv_is(channel + "OutputOffsetAI", -0)
 
     @parameterized.expand(parameterized_list(OUTPUT_CHANNELS))
-    def test_WHEN_polarity_button_pressed_THEN_correct_polarity_set_positive(self, _, channel):
+    def test_WHEN_polarity_button_pressed_THEN_correct_polarity_set_positive(
+        self, _, channel
+    ):
         self.ca.set_pv_value(channel + "OUTPUTPOLARITY:SP", 1)
         self.ca.assert_that_pv_is(channel + "OutputPolarityBI.RVAL", 1)
         self.ca.assert_that_pv_is(channel + "OUTPUTPOLARITY_OFF", 0)
 
     @parameterized.expand(parameterized_list(OUTPUT_CHANNELS))
-    def test_WHEN_polarity_button_pressed_THEN_correct_polarity_set_negative(self, _, channel):
+    def test_WHEN_polarity_button_pressed_THEN_correct_polarity_set_negative(
+        self, _, channel
+    ):
         self.ca.set_pv_value(channel + "OUTPUTPOLARITY:SP", 0)
         self.ca.assert_that_pv_is(channel + "OutputPolarityBI.RVAL", 0)
         self.ca.assert_that_pv_is(channel + "OUTPUTPOLARITY_OFF", 1)
 
     def calculate_delay(self, count, unit):
-        units_map = {"s": 1, "ms": 0.001, "us": 0.000001, "ns": 0.000000001, "ps": 0.000000000001}
+        units_map = {
+            "s": 1,
+            "ms": 0.001,
+            "us": 0.000001,
+            "ns": 0.000000001,
+            "ps": 0.000000000001,
+        }
         self.assertIn(unit, units_map, "Unexpected unit: " + str(unit))
         return round(count * units_map[unit], 12)
 
@@ -130,7 +141,9 @@ def check_channel_delay(self, chan, ref, dlay, unit):
     # Returns max delay of all channels set
     def set_all_channels(self, dataset):
         channels_to_set = DEVICE_CHANNELS[2:]
-        self.assertEqual(len(dataset), len(channels_to_set), "Incorrect dataset provided")
+        self.assertEqual(
+            len(dataset), len(channels_to_set), "Incorrect dataset provided"
+        )
         current_max = 0
         for i in range(len(dataset)):
             current_max = max(
@@ -156,7 +169,9 @@ def set_all_channels(self, dataset):
             ("H", "T0", 99, "ms"),
         ]
     )
-    def test_WHEN_delay_set_THEN_readback_correct(self, channel, reference, delay, unit):
+    def test_WHEN_delay_set_THEN_readback_correct(
+        self, channel, reference, delay, unit
+    ):
         self.set_channel_delay(channel, reference, delay, unit, True)
 
     # T1_delay = T0_delay + current_max_delay
@@ -226,7 +241,9 @@ def get_channel_width(self, channel_data, which, width=0, depth=0):
 
         # on valid settings, the depth should never reach 8
         self.assertLess(
-            depth, 8, "Endless reference loop detected in channel data. Test data invalid."
+            depth,
+            8,
+            "Endless reference loop detected in channel data. Test data invalid.",
         )
 
         # referencing T0 stops the search
@@ -245,7 +262,10 @@ def check_channel_width_matches_settings(self, channel_settings, channel):
         self.assertEqual(
             expected,
             received,
-            "Delay width incorrect, expected: " + str(expected) + ", received: " + str(received),
+            "Delay width incorrect, expected: "
+            + str(expected)
+            + ", received: "
+            + str(received),
         )
 
     # Each channel has a width which is equal to this channel's delay plus delay of referenced channel
@@ -294,7 +314,9 @@ def check_total_channel_width(self, channel_a, channel_b):
         expected = abs(round(channel_a[1] - channel_b[1], 12))
         received = self.calculate_delay(
             self.ca.get_pv_value(channel_a[0] + channel_b[0] + "DELAYWIDTH:RB"),
-            self.ca.get_pv_value(channel_a[0] + channel_b[0] + "DELAYWIDTHUNIT" ":RB.SVAL"),
+            self.ca.get_pv_value(
+                channel_a[0] + channel_b[0] + "DELAYWIDTHUNIT" ":RB.SVAL"
+            ),
         )
         self.assertEqual(
             expected,
diff --git a/system_tests/tests/dg645_llt.py b/system_tests/tests/dg645_llt.py
new file mode 100644
index 0000000..7ee6ae5
--- /dev/null
+++ b/system_tests/tests/dg645_llt.py
@@ -0,0 +1,91 @@
+# pyright: reportMissingImports=false
+import unittest
+
+from parameterized import parameterized
+from utils.channel_access import ChannelAccess
+from utils.ioc_launcher import ProcServLauncher, get_default_ioc_dir
+from utils.test_modes import TestModes
+from utils.testing import get_running_lewis_and_ioc
+
+DEVICE_PREFIX = "DG645_01"
+EMULATOR_NAME = "Dg645"
+
+IOCS = [
+    {
+        "name": DEVICE_PREFIX,
+        "directory": get_default_ioc_dir("DG645"),
+        "macros": {
+            "APPLICATION": "LITRON",
+        },
+        "emulator": EMULATOR_NAME,
+        "ioc_launcher_class": ProcServLauncher,
+    },
+]
+
+TEST_MODES = [TestModes.DEVSIM]
+
+
+class Dg645LLTTests(unittest.TestCase):
+    """
+    Tests for the Dg645 Litron Laser Timing Control IOC.
+    """
+
+    def setUp(self):
+        self._lewis, self._ioc = get_running_lewis_and_ioc(EMULATOR_NAME, DEVICE_PREFIX)
+        self.ca = ChannelAccess(device_prefix=DEVICE_PREFIX)
+
+    def test_Summed_Value(self):
+        self.ca.set_pv_value("OFFSET", 10)
+        self.ca.set_pv_value("DELAY", 20)
+        self.ca.assert_that_pv_is("SUMMED_VALUE", 30)
+
+    def test_Summed_Delay(self):
+        self.ca.set_pv_value("ADLAYSCAL", 10)
+        self.ca.set_pv_value("CDLAYSCAL", 20)
+        self.ca.set_pv_value("ADELAYBUTTON", 1)
+        self.ca.set_pv_value("CDELAYBUTTON", 1)
+        self.ca.assert_that_pv_is("SUMMED_DELAY", 30)
+
+    def test_Mode_Zero_Change_Mode_To_One(self):
+        self.ca.set_pv_value("DELAY", 10)
+        self.ca.set_pv_value("OFFSET", 5)
+        self.ca.set_pv_value("MODE", "auto")
+        self.ca.assert_that_pv_is("SET_MODE", 1)
+
+    def test_Mode_Zero_Change_Mode_To_Two(self):
+        self.ca.set_pv_value("DELAY", 5)
+        self.ca.set_pv_value("OFFSET", 5)
+        self.ca.set_pv_value("MODE", "auto")
+        self.ca.assert_that_pv_is("SET_MODE", 2)
+
+    @parameterized.expand(
+        [(0, 39900, 100, 1), (40000, 0, 0, 1), (10, -1, 0, 1), (10, -5, 5, 0)]
+    )
+    def test_Mode_One_Error_Check(self, cdelay, delay, offset, err):
+        self.ca.set_pv_value("CDELAY:SP", cdelay)
+        self.ca.set_pv_value("CDELAYUNIT:SP", "us")
+        self.ca.set_pv_value("CDELAYBUTTON", 1)
+        self.ca.set_pv_value("OFFSET", offset)
+        self.ca.set_pv_value("DELAY", delay)
+        self.ca.set_pv_value("MODE", "1")
+        self.ca.set_pv_value("ERROR.PROC", "1")
+        self.ca.assert_that_pv_is("ERROR", err)
+
+    @parameterized.expand(
+        [
+            (0, 40000, 0, 1),
+            (40000, 0, 0, 0),
+            (0, 0, 0, 1),
+            (10, -1, 0, 0),
+            (10, -5, -6, 1),
+        ]
+    )
+    def test_Mode_Two_Error_Check(self, cdelay, delay, offset, err):
+        self.ca.set_pv_value("CDELAY:SP", cdelay)
+        self.ca.set_pv_value("CDELAYUNIT:SP", "us")
+        self.ca.set_pv_value("CDELAYBUTTON", 1)
+        self.ca.set_pv_value("OFFSET", offset)
+        self.ca.set_pv_value("DELAY", delay)
+        self.ca.set_pv_value("MODE", "2")
+        self.ca.set_pv_value("ERROR.PROC", "1")
+        self.ca.assert_that_pv_is("ERROR", err)