diff --git a/bs/BusTypes.bs b/bs/BusTypes.bs
index e7cba2c..422ed9e 100644
--- a/bs/BusTypes.bs
+++ b/bs/BusTypes.bs
@@ -1,4 +1,10 @@
-package BusTypes(BusVal, TransactionSize) where
+package BusTypes(
+    BusVal(..),
+    BusError(..),
+    TransactionSize(..),
+    ReadRequest(..),
+    WriteRequest(..)
+    ) where
 
 import Types
 
@@ -29,5 +35,34 @@ data ReadRequest = ReadRequest Addr TransactionSize
 data WriteRequest = WriteRequest Addr BusVal
     deriving (Bits, Eq, FShow)
 
+type ReadResponse = Either BusError BusVal
+type WriteResponse = Either BusError ()
+
+data BusRequest
+  = BusReadRequest      ReadRequest
+  | WriteReadRequest    WriteRequest
+  deriving (Bits, Eq, FShow)
+
+data BusResponse
+  = BusReadResponse     ReadResponse
+  | BusWriteResponse    WriteResponse
+  deriving (Bits, Eq, FShow)
+
+interface BusMaster =
+  -- The Bus arbiter will call the Bus Client's request method
+  -- if and only if it's the Bus Client's turn to make a request, and the Bus Client
+  -- has a request to make.
+  -- It is up to the BusMaster to guard it's request method such that calling
+  -- it's request method is only valid when the BusMaster has a request to make.
+  -- This has implications about for the implementor of BusMaster, namely, that it
+  -- should hold its request until it's request method gets called.
+  request  :: BusRequest
+  -- From the client's perspective, the response should not be called until
+  -- the client is ready to accept the response. In other words, response
+  -- should be guarded by the client.
+  response :: BusResponse -> Action
+
+type Token = UInt 5
+
 a :: UInt 5
 a = 3
diff --git a/bs/Top.bs b/bs/Top.bs
index b1f7105..5efb1d4 100644
--- a/bs/Top.bs
+++ b/bs/Top.bs
@@ -6,6 +6,7 @@ import Serializer
 import BRAM
 import CBindings
 import Bus
+import List
 
 type FCLK = 25000000
 type BAUD = 9600
@@ -16,19 +17,65 @@ interface ITop = {
  ;ftdi_txd :: Bit 1 -> Action {-# always_ready , always_enabled  #-}
 };
 
+interface BusClient =
+  request  :: Bit 1
+  response :: Bit 1 -> Action
+
+mkBusClient :: Module BusClient
+mkBusClient = module
+  reqReg :: Reg (Bit 1) <- mkReg 0
+  return $
+    interface BusClient
+      request = reqReg
+      response resp = do
+        reqReg := 0  -- Reset request after receiving response
+
+interface Bus =
+  request  :: Bit 1 -> Action
+  response :: Bit 1
+
+mkBus :: Module Bus
+mkBus = module
+  respReg :: Reg (Bit 1) <- mkReg 0
+  return $
+    interface Bus
+      request req = do
+        respReg := req  -- Simple pass-through for this example
+      response = respReg
+
+-- -- Function to connect Bus to BusClient
+connectBusToClient :: Bus -> BusClient -> Rules
+connectBusToClient bus client =
+  rules
+    "busConnection": when True ==> do
+      bus.request client.request
+      client.response bus.response
+
+-- need to implement mkBus
+
+-- need function that can connect Bus to BusClient
+
 mkTop :: Module ITop
 mkTop = do
   fileHandle   :: Handle <- openFile "compile.log" WriteMode
   deserializer :: IDeserializer FCLK BAUD <- mkDeserialize fileHandle
   serializer   :: ISerializer FCLK BAUD <- mkSerialize fileHandle
   core         :: Core FCLK <- mkCore
+
+  bus          :: Bus <- mkBus
+  busClient    :: BusClient <- mkBusClient
+  let a :: List Integer = 1 :> 2 :> Nil
+      b = length a
+
   persistLed  :: Reg (Bit 8) <- mkReg 0
   messageM $ "Hallo!!" + (realToString 5)
 
-  -- refactor such that the following rules are let-bound to
-  -- `attachIO` identifier
+  -- need to instantiate a Bus and BusClient
+  addRules $ connectBusToClient bus busClient
+
   addRules $
     rules
+      -- need new rule that always connects Bus to BusClient
       "coreLedO" : when True ==>
         persistLed := core.getLed