initial support for exceptions

hs/BusTypes.hs

@@ -3,7 +3,6 @@ module BusTypes(
     BusError(..),
     TransactionSize(..),
     ReadRequest(..),
-    BusResponse(..),
     BusVal(..),
     ) where
 
@@ -28,11 +27,6 @@ data TransactionSize
 data ReadRequest = Request Addr TransactionSize
     deriving (Generic, Show, Eq, NFDataX)
 
-data BusResponse a
-    = Result a
-    | Error BusError
-    deriving (Generic, Show, Eq, NFDataX)
-
 data BusVal
     = BusByte Byte
     | BusHalfWord HalfWord