diff --git a/bs/Bus.bs b/bs/Bus.bs
new file mode 100644
index 0000000..0faaa54
--- /dev/null
+++ b/bs/Bus.bs
@@ -0,0 +1,7 @@
+package Bus(a) where
+
+import Types
+import BusTypes
+
+a :: UInt 5
+a = 3
diff --git a/bs/BusTypes.bs b/bs/BusTypes.bs
new file mode 100644
index 0000000..e7cba2c
--- /dev/null
+++ b/bs/BusTypes.bs
@@ -0,0 +1,33 @@
+package BusTypes(BusVal, TransactionSize) where
+
+import Types
+
+data BusError
+    = UnMapped
+    | UnAligned
+    deriving (Bits, Eq, FShow)
+
+data TransactionSize
+    = SizeByte
+    | SizeHalfWord
+    | SizeFullWord
+    | SizeDoubleWord
+    | SizeQuadWord
+    deriving (Bits, Eq, FShow)
+
+data BusVal
+    = BusByte Byte
+    | BusHalfWord HalfWord
+    | BusFullWord FullWord
+    | BusDoubleWord DoubleWord
+    | BusQuadWord QuadWord
+    deriving (Bits, Eq, FShow)
+
+data ReadRequest = ReadRequest Addr TransactionSize
+    deriving (Bits, Eq, FShow)
+
+data WriteRequest = WriteRequest Addr BusVal
+    deriving (Bits, Eq, FShow)
+
+a :: UInt 5
+a = 3
diff --git a/bs/Top.bs b/bs/Top.bs
index a360a20..b1f7105 100644
--- a/bs/Top.bs
+++ b/bs/Top.bs
@@ -5,6 +5,7 @@ import Core
 import Serializer
 import BRAM
 import CBindings
+import Bus
 
 type FCLK = 25000000
 type BAUD = 9600
@@ -24,7 +25,7 @@ mkTop = do
   persistLed  :: Reg (Bit 8) <- mkReg 0
   messageM $ "Hallo!!" + (realToString 5)
 
-  -- refactor such that the following rules are let-bound to 
+  -- refactor such that the following rules are let-bound to
   -- `attachIO` identifier
   addRules $
     rules
@@ -43,7 +44,7 @@ mkTop = do
   return $
     interface ITop
       ftdi_rxd =  serializer.bitLineOut
-      ftdi_txd bitIn =  
+      ftdi_txd bitIn =
            do
              deserializer.putBitIn bitIn
       led =  persistLed
@@ -73,4 +74,4 @@ mkSim = do
         do
           restoreTerminal
           $display "GOT CTRL+C"
-          $finish
\ No newline at end of file
+          $finish
diff --git a/bs/Types.bs b/bs/Types.bs
new file mode 100644
index 0000000..bbb6903
--- /dev/null
+++ b/bs/Types.bs
@@ -0,0 +1,15 @@
+package Types(
+    Pc, Insn, Addr,
+    Byte, HalfWord, FullWord, DoubleWord, QuadWord
+    )
+    where
+
+type Byte       = UInt 8
+type HalfWord   = UInt 16
+type FullWord   = UInt 32
+type DoubleWord = UInt 64
+type QuadWord   = UInt 128
+type Insn       = FullWord
+
+type Pc         = DoubleWord
+type Addr       = DoubleWord