diff --git a/pythoncardx/framework/tlv/__init__.py b/pythoncardx/framework/tlv/__init__.py
index b9c6c86..6a3eb00 100644
--- a/pythoncardx/framework/tlv/__init__.py
+++ b/pythoncardx/framework/tlv/__init__.py
@@ -1,4 +1,4 @@
-from javacard.framework import CardRuntimeException
+from pythoncard.framework import CardRuntimeException
 
 class TLVException(CardRuntimeException):
     EMPTY_TAG = 0
@@ -13,6 +13,8 @@ class TLVException(CardRuntimeException):
     TLV_LENGTH_GREATER_THAN_32767 = 9
     TLV_SIZE_GREATER_THAN_32767 = 10
 
-from pythoncard.framework.tlv import bertag
+from pythoncardx.framework.tlv import bertag
 
 BERTag = bertag.BERTag
+PrimitiveBERTag = bertag.PrimitiveBERTag
+ConstructedBERTag = bertag.ConstructedBERTag
diff --git a/pythoncardx/framework/tlv/bertag.py b/pythoncardx/framework/tlv/bertag.py
index 6e9fc9b..4757cca 100644
--- a/pythoncardx/framework/tlv/bertag.py
+++ b/pythoncardx/framework/tlv/bertag.py
@@ -1,6 +1,11 @@
-"""
-It's 2.2 ... not that prioritary ...
-"""
+from pythoncardx.framework.tlv import TLVException
+
+class toBytes(object):
+    def __get__(self, obj, objtype=None):
+        if obj is not None:
+            return obj._toBytesBound
+        else:
+            return BERTag._toBytesStatic
 
 class BERTag(object):
     BER_TAG_CLASS_MASK_APPLICATION = 0
@@ -11,16 +16,87 @@ class BERTag(object):
     BER_TAG_TYPE_PRIMITIVE = 5
 
     def __init__(self):
-        self._tag = 0
-        self._length = 0
-        self._value = []
-    
-    def equals(self, otherTag):
-        pass
-
-    @classmethod
-    def getInstance(classs, bArray, bOff):
-        c = classs()
-        c.init(bArray, bOff)
-        return c
+        self._tagClass = 0
+        self._tagNumber = 0
+
+    def init(self, bArray, bOff):
+        self._tagClass = bArray[bOff] >> 6
+        if (bArray[bOff] & 0x1f) == 0x1f:
+            self._tagNumber = 0
+            bOff += 1
+            while (bArray[bOff] & 0x80) == 0x80:
+                self._tagNumber = self._tagNumber << 7
+                self._tagNumber += bArray[bOff] & 0x7f
+                bOff += 1
+            self._tagNumber = self._tagNumber << 7
+            self._tagNumber += bArray[bOff] & 0x7f
+        else:
+            self._tagNumber = bArray[bOff] & 0x1f
+
+    def _toBytesBound(self, outBuf, bOffset):
+        outBuf[bOffset] = self._tagClass << 6
+        outBuf[bOffset] += self._PC << 5
+        if self._tagNumber <= 30:
+            outBuf[bOffset] += self._tagNumber
+            return 1
+        else:
+            tagNumber = self._tagNumber
+            outBuf[bOffset] += 0x1f
+            chunks = []
+            while tagNumber > 0:
+                chunks.append(tagNumber & 0x7f)
+                tagNumber = tagNumber >> 7
+            bLen = 1
+            for i in reversed(chunks):
+                outBuf[bOffset+bLen] = 0x80
+                outBuf[bOffset+bLen] += i
+                bLen += 1
+            #clear the high bit on the last part
+            outBuf[bOffset+bLen-1] &= 0x7f
+            return bLen
+
+    @staticmethod
+    def _toBytesStatic(tagClass, isConstructed, tagNumber, outArray, bOff):
+        tag = {True: ConstructedBERTag,
+               False: PrimitiveBERTag}[isConstructed]()
+        tag.init(tagClass, tagNumber)
+        return tag.toBytes(outArray, bOff)
+
+    toBytes = toBytes()
+
+class PrimitiveBERTag(BERTag):
+    def __init__(self):
+        BERTag.__init__(self)
+        self._PC = 0 # primitive
+
+    def init(self, param1, param2):
+        self._tagClass = None
+        self._tagNumber = None
+        if isinstance(param1, list):
+            if (param1[param2] & 0x20) == 0x20:
+                # constructed tag
+                raise TLVException(TLVException.MALFORMED_TAG)
+            BERTag.init(self, param1, param2)
+        else:
+            tagClass = param1
+            tagNumber = param2
+            self._tagClass = tagClass
+            self._tagNumber = tagNumber
+
+class ConstructedBERTag(BERTag):
+    def __init__(self):
+        BERTag.__init__(self)
+        self._PC = 1 # constructed
+
+    def init(self, param1, param2):
+        self._tagClass = None
+        self._tagNumber = None
+        if isinstance(param1, list):
+            if (param1[param2] & 0x20) == 0:
+                # primitive tag
+                raise TLVException(TLVException.MALFORMED_TAG)
+            BERTag.init(self, param1, param2)
+        else:
+            self._tagClass = param1
+            self._tagNumber = param2
     
diff --git a/test/testTLVTag.py b/test/testTLVTag.py
new file mode 100644
index 0000000..2b68933
--- /dev/null
+++ b/test/testTLVTag.py
@@ -0,0 +1,15 @@
+import unittest
+
+from pythoncardx.framework.tlv import BERTag, PrimitiveBERTag, ConstructedBERTag
+
+class BERTagTest(unittest.TestCase):
+
+    def testtoBytes(self):
+        array = [0 for i in xrange(10)]
+        self.assertEquals(1, BERTag.toBytes(1, False, 5, array, 0))
+        self.assertEquals(0x45, array[0])
+
+        self.assertEquals(3, BERTag.toBytes(1, False, 0x3fff, array, 0))
+        self.assertEquals(0x5f, array[0])
+        self.assertEquals(0xff, array[1])
+        self.assertEquals(0x7f, array[2])