diff --git a/grmn/gcd.py b/grmn/gcd.py
index c751882..0110509 100644
--- a/grmn/gcd.py
+++ b/grmn/gcd.py
@@ -1,170 +1,17 @@
 # -*- coding: utf-8 -*-
 # Thanks to TurboCCC and kunix for all your work!
 
-from . import chksum
-from . import devices
-from binascii import hexlify
-from struct import pack, unpack
-import sys
+from .tlv import TLV, TLV6, TLV7
 
 GCD_SIG = b"G\x41RM\x49Nd\00"
 DEFAULT_COPYRIGHT = b"Copyright 1996-2017 by G\x61rm\x69n Ltd. or its subsidiaries."
 DEFAULT_FIRST_PADDING = 21
 DEFAULT_ALIGN = 0x1000    # second padding block pads until 0x1000
 
-TLV_TYPES = {
-    0x0001: "Checksum rectifier",
-    0x0002: "Padding",
-    0x0003: "Part number?",
-    0x0005: "Copyright notice",
-    0x0006: "Block Type 7 format definition",
-    0x0007: "Binary descriptor",
-    0x0008: "Binary Region 0C (boot.bin)",
-    0x0401: "Binary Component Firmware (SensorHub, ANT_BLE_BT, GPS, WiFi)",
-    0x0505: "Binary Region 05",
-    0x0555: "Binary Region 55",
-    0x0557: "Binary Region 57",
-    0x02bd: "Binary Region 0E (fw_all.bin)",
-    0xffff: "EOF marker",
-}
-
 # Typical structure:
 # first 0x1000 Bytes: GCD_SIG > 0x0001 > 0x0002 > 0x0003 > 0x0005 > 0x0001 > 0x0002
 # then: 0x0001 > ( 0x0006 > 0x0007 > 0x???? > 0x0001 ... ) > 0xffff
 
-class TLV:
-    def __init__(self, type_id: int, expected_length: int, value=None, offset: int=None):
-        self.type_id = type_id
-        self.offset = offset
-        self.comment = TLV_TYPES.get(type_id, "Type {:04x} / {:d}".format(type_id, type_id))
-        self.length = expected_length
-        self.value = None
-        self.is_parsed = False
-        if value is not None:
-            self.value = bytes(value)
-
-    @staticmethod
-    def factory(header: bytes, offset: int = None):
-        (type_id, length) = unpack("<HH", header)
-        if type_id == 0x0006:
-            new_tlv = TLV6(type_id, length)
-        elif type_id == 0x0007:
-            new_tlv = TLV7(type_id, length)
-        else:
-            new_tlv = TLV(type_id, length)
-        new_tlv.offset = offset
-        return new_tlv
-
-    def __str__(self):
-        plural = ""
-        if self.length != 1:
-            plural = "s"
-        return "TLV Type {:04x} at 0x{:x}, {:d} Byte{} - {}".format(self.type_id, self.offset, self.length, plural, self.comment)
-
-    def set_value(self, new_value: bytes):
-        self.value = new_value
-
-    def get_length(self):
-        return self.length
-
-    def get_actual_length(self):
-        if self.value is None:
-            return 0
-        return len(self.value)
-
-    def get_record_length(self):
-        # Length including record definition
-        return self.get_actual_length() + 4
-
-    def get_value(self):
-        return self.value
-
-    def get(self):
-        header = pack("HH", self.type_id, self.get_actual_length())
-        if self.value is None:
-            return header
-        return header + self.value
-
-class TLV6(TLV):
-    """
-    Describes following TLV7:
-    http://www.gpspassion.com/forumsen/topic.asp?TOPIC_ID=137838&whichpage=12
-    """
-
-    # Field ids in Type 6 payloads (describe Type 7 data format)
-    # First nibble might be data type: 0 = B, 1 = H, 2 = L
-    FIELD_TYPES = {
-        0x000a: ["B", "XOR flag/value"],
-        0x000b: ["B", "Reset/Downgrade flag"],
-        0x1009: ["H", "Device hw_id"],
-        0x100a: ["H", "Block type"],
-        0x100d: ["H", "Firmware version"],
-        0x1014: ["H", "Field 1014"],
-        0x1015: ["H", "Field 1015"],
-        0x1016: ["H", "Field 1016 (WiFi fw)"],
-        0x2015: ["L", "Block size"],
-        0x5003: ["", "End of definition marker"],
-    }
-
-    def parse(self):
-        if len(self.value) % 2 != 0:
-            raise Exception("Invalid TLV6 payload length!")
-
-        self.fids = []
-        self.format = ""
-        self.fields = []
-
-        for i in range(0, len(self.value), 2):
-            fid = unpack("H", self.value[i:i+2])[0]
-            fdef = self.FIELD_TYPES[fid]
-            self.fids.append(fid)
-            self.format += fdef[0]
-            self.fields.append(fdef[1])
-
-        self.is_parsed = True
-
-    def __str__(self):
-        txt = super().__str__()
-        if not self.is_parsed:
-            self.parse()
-        for i, fid in enumerate(self.fids):
-            txt += "\n  - Field {:d}: {:04x} - {}".format(i+1, fid, self.fields[i])
-        return txt
-
-class TLV7(TLV):
-    def __init__(self, type_id: int, expected_length: int, value=None, offset: int=None):
-        super().__init__(type_id, expected_length, value, offset)
-        self.tlv6 = None
-        self.attr = []
-
-    def set_tlv6(self, tlv6: TLV6):
-        self.tlv6 = tlv6
-
-    def parse(self):
-        if not self.tlv6.is_parsed:
-            # Make sure we have the structure analysed
-            self.tlv6.parse()
-        values = unpack("<" + self.tlv6.format, self.value)
-        for i, v in enumerate(values):
-            fid = self.tlv6.fids[i]
-            self.attr.append((fid, v))
-        self.is_parsed = True
-
-    def __str__(self):
-        txt = super().__str__()
-        if not self.is_parsed:
-            self.parse()
-        for i, pair in enumerate(self.attr):
-            fdesc = self.tlv6.fields[i]
-            (fid, v) = pair
-            if fid == 0x1009:
-                txt += "\n  - Field {:d}: {:>20}: 0x{:04x} / {:d} ({})".format(i+1, fdesc, v, v, devices.DEVICES.get(v, "Unknown device"))
-            elif fid == 0x2015:
-                txt += "\n  - Field {:d}: {:>20}: {} Bytes".format(i+1, fdesc, v)
-            else:
-                txt += "\n  - Field {:d}: {:>20}: 0x{:04x} / {:d}".format(i+1, fdesc, v, v)
-        return txt
-
 class Gcd:
     def __init__(self, filename: str=None):
         self.filename = filename
diff --git a/grmn/tlv.py b/grmn/tlv.py
new file mode 100644
index 0000000..b634acc
--- /dev/null
+++ b/grmn/tlv.py
@@ -0,0 +1,154 @@
+# -*- coding: utf-8 -*-
+
+from . import devices
+from struct import pack, unpack
+
+TLV_TYPES = {
+    0x0001: "Checksum rectifier",
+    0x0002: "Padding",
+    0x0003: "Part number?",
+    0x0005: "Copyright notice",
+    0x0006: "Block Type 7 format definition",
+    0x0007: "Binary descriptor",
+    0x0008: "Binary Region 0C (boot.bin)",
+    0x0401: "Binary Component Firmware (SensorHub, ANT_BLE_BT, GPS, WiFi)",
+    0x0505: "Binary Region 05",
+    0x0555: "Binary Region 55",
+    0x0557: "Binary Region 57",
+    0x02bd: "Binary Region 0E (fw_all.bin)",
+    0xffff: "EOF marker",
+}
+
+class TLV:
+    def __init__(self, type_id: int, expected_length: int, value=None, offset: int=None):
+        self.type_id = type_id
+        self.offset = offset
+        self.comment = TLV_TYPES.get(type_id, "Type {:04x} / {:d}".format(type_id, type_id))
+        self.length = expected_length
+        self.value = None
+        self.is_parsed = False
+        if value is not None:
+            self.value = bytes(value)
+
+    @staticmethod
+    def factory(header: bytes, offset: int = None):
+        (type_id, length) = unpack("<HH", header)
+        if type_id == 0x0006:
+            new_tlv = TLV6(type_id, length)
+        elif type_id == 0x0007:
+            new_tlv = TLV7(type_id, length)
+        else:
+            new_tlv = TLV(type_id, length)
+        new_tlv.offset = offset
+        return new_tlv
+
+    def __str__(self):
+        plural = ""
+        if self.length != 1:
+            plural = "s"
+        return "TLV Type {:04x} at 0x{:x}, {:d} Byte{} - {}".format(self.type_id, self.offset, self.length, plural, self.comment)
+
+    def set_value(self, new_value: bytes):
+        self.value = new_value
+
+    def get_length(self):
+        return self.length
+
+    def get_actual_length(self):
+        if self.value is None:
+            return 0
+        return len(self.value)
+
+    def get_record_length(self):
+        # Length including record definition
+        return self.get_actual_length() + 4
+
+    def get_value(self):
+        return self.value
+
+    def get(self):
+        header = pack("HH", self.type_id, self.get_actual_length())
+        if self.value is None:
+            return header
+        return header + self.value
+
+class TLV6(TLV):
+    """
+    Describes following TLV7:
+    http://www.gpspassion.com/forumsen/topic.asp?TOPIC_ID=137838&whichpage=12
+    """
+
+    # Field ids in Type 6 payloads (describe Type 7 data format)
+    # First nibble might be data type: 0 = B, 1 = H, 2 = L
+    FIELD_TYPES = {
+        0x000a: ["B", "XOR flag/value"],
+        0x000b: ["B", "Reset/Downgrade flag"],
+        0x1009: ["H", "Device hw_id"],
+        0x100a: ["H", "Block type"],
+        0x100d: ["H", "Firmware version"],
+        0x1014: ["H", "Field 1014"],
+        0x1015: ["H", "Field 1015"],
+        0x1016: ["H", "Field 1016 (WiFi fw)"],
+        0x2015: ["L", "Block size"],
+        0x5003: ["", "End of definition marker"],
+    }
+
+    def parse(self):
+        if len(self.value) % 2 != 0:
+            raise Exception("Invalid TLV6 payload length!")
+
+        self.fids = []
+        self.format = ""
+        self.fields = []
+
+        for i in range(0, len(self.value), 2):
+            fid = unpack("H", self.value[i:i+2])[0]
+            fdef = self.FIELD_TYPES[fid]
+            self.fids.append(fid)
+            self.format += fdef[0]
+            self.fields.append(fdef[1])
+
+        self.is_parsed = True
+
+    def __str__(self):
+        txt = super().__str__()
+        if not self.is_parsed:
+            self.parse()
+        for i, fid in enumerate(self.fids):
+            txt += "\n  - Field {:d}: {:04x} - {}".format(i+1, fid, self.fields[i])
+        return txt
+
+class TLV7(TLV):
+    def __init__(self, type_id: int, expected_length: int, value=None, offset: int=None):
+        super().__init__(type_id, expected_length, value, offset)
+        self.tlv6 = None
+        self.attr = []
+
+    def set_tlv6(self, tlv6: TLV6):
+        self.tlv6 = tlv6
+
+    def parse(self):
+        if not self.tlv6.is_parsed:
+            # Make sure we have the structure analysed
+            self.tlv6.parse()
+        values = unpack("<" + self.tlv6.format, self.value)
+        for i, v in enumerate(values):
+            fid = self.tlv6.fids[i]
+            self.attr.append((fid, v))
+        self.is_parsed = True
+
+    def __str__(self):
+        txt = super().__str__()
+        if not self.is_parsed:
+            self.parse()
+        for i, pair in enumerate(self.attr):
+            fdesc = self.tlv6.fields[i]
+            (fid, v) = pair
+            if fid == 0x1009:
+                txt += "\n  - Field {:d}: {:>20}: 0x{:04x} / {:d} ({})".format(i+1, fdesc, v, v, devices.DEVICES.get(v, "Unknown device"))
+            elif fid == 0x2015:
+                txt += "\n  - Field {:d}: {:>20}: {} Bytes".format(i+1, fdesc, v)
+            else:
+                txt += "\n  - Field {:d}: {:>20}: 0x{:04x} / {:d}".format(i+1, fdesc, v, v)
+        return txt
+