diff --git a/hs/Bus.hs b/hs/Bus.hs
index 37130de..bb7b031 100644
--- a/hs/Bus.hs
+++ b/hs/Bus.hs
@@ -1,25 +1,45 @@
 {-# OPTIONS_GHC -Wno-unrecognised-pragmas #-}
-module Bus() where
+module Bus(
+  Peripherals(..),
+  ReadResponse,
+  WriteResponse,
+  Bus.read,
+  Bus.write,
+) where
 
 import Clash.Prelude
 
 import Peripherals.Ram(Ram, RamLine, read, RamAddr)
 import Peripherals.Uart(UartAddr, read, write)
-import Machine(Peripherals(..))
+
 import BusTypes(
     BusError(..),
     TransactionSize(..),
     ReadRequest(..),
     BusResponse(..),
     BusVal(..),
-    ReadResponse(..),
-    WriteResponse(..)
   )
 import Types(Addr,
              Byte, HalfWord, FullWord, DoubleWord, QuadWord)
-import Peripherals.Ram(read, bytesInRam)
+import Peripherals.Ram(read, write, bytesInRam)
 import Distribution.Types.UnitId (DefUnitId(unDefUnitId))
 
+data Peripherals = Peripherals
+  {
+      ram  :: Ram
+  }
+  deriving (Generic, Show, Eq, NFDataX)
+
+type ReadResponse = Either BusError BusVal
+type WriteResponse = Either BusError Peripherals
+
+busValToTransactionSize :: BusVal -> TransactionSize
+busValToTransactionSize (BusByte _)       = SizeByte
+busValToTransactionSize (BusHalfWord _)   = SizeHalfWord
+busValToTransactionSize (BusFullWord _)   = SizeFullWord
+busValToTransactionSize (BusDoubleWord _) = SizeDoubleWord
+busValToTransactionSize (BusQuadWord _)   = SizeQuadWord
+
 alignCheck :: Addr -> TransactionSize -> Bool
 alignCheck addr SizeByte       = True
 alignCheck addr SizeHalfWord   = addr `mod` 2 == 0
@@ -50,15 +70,24 @@ read (Request addr size) peripherals
       uartAddr :: UartAddr
       uartAddr = resize uartAddrNoOffset
 
--- write :: BusVal -> Addr -> Peripherals -> IO WriteResponse
--- write val addr peripherals
---   | (addr >= uartStart) && (addr <= uartEnd) =
---       WriteResponse . Result <$> Peripherals.Uart.write val uartAddr
---     where
---       ramAddrNoOffset = addr - ramStart
---       ramAddr :: RamAddr
---       ramAddr = resize ramAddrNoOffset
+write :: BusVal -> Addr -> Peripherals -> IO WriteResponse
+write val addr peripherals
+  | not (alignCheck addr $ busValToTransactionSize val) = return $ Left UnAligned
+  | (addr >= uartStart) && (addr <= uartEnd) =
+      do
+        Peripherals.Uart.write val uartAddr
+        return $ Right peripherals
+  | (addr >= ramStart) && (addr <= ramEnd) =
+      return $ Right $
+        peripherals {
+          ram = Peripherals.Ram.write val ramAddr (ram peripherals)
+          }
+  | otherwise = return $ Left UnMapped
+    where
+      ramAddrNoOffset = addr - ramStart
+      ramAddr :: RamAddr
+      ramAddr = resize ramAddrNoOffset
 
---       uartAddrNoOffset = addr - uartStart
---       uartAddr :: UartAddr
---       uartAddr = resize uartAddrNoOffset
+      uartAddrNoOffset = addr - uartStart
+      uartAddr :: UartAddr
+      uartAddr = resize uartAddrNoOffset
diff --git a/hs/BusTypes.hs b/hs/BusTypes.hs
index 3c30968..98a3cd6 100644
--- a/hs/BusTypes.hs
+++ b/hs/BusTypes.hs
@@ -5,8 +5,6 @@ module BusTypes(
     ReadRequest(..),
     BusResponse(..),
     BusVal(..),
-    ReadResponse(..),
-    WriteResponse(..)
     ) where
 
 import Clash.Prelude
@@ -42,11 +40,3 @@ data BusVal
     | BusDoubleWord DoubleWord
     | BusQuadWord QuadWord
     deriving (Generic, Show, Eq, NFDataX)
-
--- newtype ReadResponse = ReadResponse (BusResponse BusVal)
---     deriving (Generic, Show, Eq, NFDataX)
-
-type ReadResponse = Either BusError BusVal
-
-newtype WriteResponse = WriteResponse (BusResponse ())
-    deriving (Generic, Show, Eq, NFDataX)
diff --git a/hs/Cpu.hs b/hs/Cpu.hs
new file mode 100644
index 0000000..80018ce
--- /dev/null
+++ b/hs/Cpu.hs
@@ -0,0 +1,37 @@
+{-# LANGUAGE DataKinds #-}
+{-# LANGUAGE NumericUnderscores #-}
+
+module Cpu(
+  RISCVCPU(..),
+  Endian(..),
+  riscvCPUInit) where
+
+import Clash.Prelude
+import Types(Pc, Mem)
+import RegFiles(GPR, FPR, CSR, gprInit, fprInit, csrInit)
+import Peripherals.Ram(Ram)
+
+data Endian = Big | Little
+  deriving (Generic, Show, Eq, NFDataX)
+
+data PrivilegeLevel
+  = MachineMode
+  | SuperVisorMode
+  | UserMode
+  deriving (Generic, Show, Eq, NFDataX)
+
+data RISCVCPU = RISCVCPU
+  { pc  :: Pc,
+    gpr :: GPR,
+    fpr :: FPR,
+    privilegeLevel :: PrivilegeLevel
+  }
+  deriving (Generic, Show, Eq, NFDataX)
+
+riscvCPUInit :: RISCVCPU
+riscvCPUInit =
+  RISCVCPU
+    0
+    gprInit
+    fprInit
+    MachineMode
diff --git a/hs/Fetch.hs b/hs/Fetch.hs
index b5c12a8..d4c63b4 100644
--- a/hs/Fetch.hs
+++ b/hs/Fetch.hs
@@ -13,6 +13,7 @@ import Clash.Prelude
       Bits(shiftR, (.&.)) )
 import Types(Mem, Addr, Insn)
 import Util(endianSwapWord)
+import Bus(ReadResponse, WriteResponse, read)
 
 data FetchResult  = Instruction Insn
                   | Misaligned Addr
diff --git a/hs/Machine.hs b/hs/Machine.hs
deleted file mode 100644
index d65c7d3..0000000
--- a/hs/Machine.hs
+++ /dev/null
@@ -1,75 +0,0 @@
-{-# LANGUAGE DataKinds #-}
-{-# LANGUAGE NumericUnderscores #-}
-
-module Machine(
-  Machine(..),
-  RISCVCPU(..),
-  Peripherals(..),
-  Endian(..),
-  machineInit) where
-
-import Clash.Prelude
-import Types(Pc, Mem)
-import RegFiles(GPR, FPR, CSR, gprInit, fprInit, csrInit)
-import Peripherals.Ram(Ram)
-
-data Endian = Big | Little
-  deriving (Generic, Show, Eq, NFDataX)
-
-data PrivilegeLevel
-  = MachineMode
-  | SuperVisorMode
-  | UserMode
-  deriving (Generic, Show, Eq, NFDataX)
-
-data Peripherals = Peripherals
-  {
-      ram  :: Ram
-  }
-  deriving (Generic, Show, Eq, NFDataX)
-
-data RISCVCPU = RISCVCPU
-  { pc  :: Pc,
-    gpr :: GPR,
-    fpr :: FPR,
-    privilegeLevel :: PrivilegeLevel
-  }
-  deriving (Generic, Show, Eq, NFDataX)
-
-data Machine = Machine
-  { cpu :: RISCVCPU,
-    peripherals :: Peripherals
-  }
-  deriving (Generic, Show, Eq, NFDataX)
-
-riscvCPUInit :: RISCVCPU
-riscvCPUInit =
-  RISCVCPU
-    0
-    gprInit
-    fprInit
-    MachineMode
-
-machineInit :: Peripherals -> Machine
-machineInit peripherals =
-  Machine
-    riscvCPUInit
-    peripherals
-
-memInit :: Vec 14 (Unsigned 32)
-memInit =
-     0x0000A03C
-  :> 0x3000A5E8
-  :> 0x1A002038
-  :> 0x18002598
-  :> 0x10002588
-  :> 0x01002170
-  :> 0xF8FF8141
-  :> 0x08002588
-  :> 0x01002138
-  :> 0x00002598
-  :> 0xE8FFFF4B
-  :> 0x00000060
-  :> 0x002000C0
-  :> 0x00000000
-  :> Nil
diff --git a/hs/Peripherals/Ram.hs b/hs/Peripherals/Ram.hs
index a7e8dfe..df3b949 100644
--- a/hs/Peripherals/Ram.hs
+++ b/hs/Peripherals/Ram.hs
@@ -10,7 +10,8 @@ module Peripherals.Ram(
   RamLine,
   bytesInRam,
   read,
-  write) where
+  write,
+  ) where
 
 import Clash.Prelude hiding (read)
 import qualified Prelude as P
@@ -23,8 +24,6 @@ import Types(Addr,
 import BusTypes(
     TransactionSize(..),
     BusVal(..),
-    ReadResponse(..),
-    WriteResponse(..)
   )
 
 -- vector depth has to be known statically at compile time
@@ -85,9 +84,50 @@ readDoubleWordHelper ram addr = bitCoerce $ bitCoerce word0 ++# bitCoerce word1
     word0 = readFullWordHelper ram addr
     word1 = readFullWordHelper ram (addr + 1)
 
--- write :: BusVal -> UartAddr -> IO ()
-write :: Ram -> RamAddr -> RamLine -> Ram
-write ram addr value = replace addr value ram
+write :: BusVal -> RamAddr -> Ram -> Ram
+write (BusByte byte) addr ram = replace addr updatedWord ram
+  where
+    word = ram !! addr
+    byteOffset :: BitVector 2
+    byteOffset = slice d1 d0 addr
+    updatedWord = case byteOffset of
+      0b00 -> setSlice d31 d24 (pack byte) word
+      0b01 -> setSlice d23 d16 (pack byte) word
+      0b10 -> setSlice d15 d8  (pack byte) word
+      0b11 -> setSlice d7 d0   (pack byte) word
+
+write (BusHalfWord halfWord) addr ram = replace addr updatedWord ram
+  where
+    word = ram !! addr
+    halfWordOffset :: Unsigned 1
+    halfWordOffset = unpack $ slice d0 d0 addr
+    updatedWord = case halfWordOffset of
+      0b0 -> setSlice d31 d16 (pack halfWord) word
+      0b1 -> setSlice d15 d0  (pack halfWord) word
+
+write (BusFullWord fullWord) addr ram = replace addr fullWord ram
+
+write (BusDoubleWord doubleWord) addr ram = ram''
+  where
+    (word0, word1) = bitCoerce doubleWord
+    ram' = replace addr word0 ram
+    ram'' = replace (addr + 1) word1 ram'
+
+write (BusQuadWord quadWord) addr ram = ram''''
+  where
+    (dword0 :: DoubleWord, dword1 :: DoubleWord) =
+      bitCoerce quadWord
+
+    (word0 :: FullWord, word1 :: FullWord) =
+      bitCoerce dword0
+
+    (word2 :: FullWord, word3 :: FullWord) =
+      bitCoerce dword1
+
+    ram' = replace addr word0 ram
+    ram'' = replace (addr + 1) word1 ram'
+    ram''' = replace (addr + 2) word2 ram''
+    ram'''' = replace (addr + 3) word3 ram'''
 
 initRamFromFile :: FilePath -> IO (Maybe Ram)
 initRamFromFile filePath =
diff --git a/hs/Peripherals/Uart.hs b/hs/Peripherals/Uart.hs
index 15599da..9fa718b 100644
--- a/hs/Peripherals/Uart.hs
+++ b/hs/Peripherals/Uart.hs
@@ -17,8 +17,6 @@ import Peripherals.UartCFFI (
 import BusTypes (
     TransactionSize(..),
     BusVal(..),
-    ReadResponse(..),
-    WriteResponse(..)
   )
 import GHC.Generics (URec(UAddr), Generic (from))
 
diff --git a/hs/Simulation.hs b/hs/Simulation.hs
index c8ae6cc..8d810ca 100644
--- a/hs/Simulation.hs
+++ b/hs/Simulation.hs
@@ -9,11 +9,11 @@ import qualified Prelude as P
 import Peripherals.Setup(setupPeripherals, InitializedPeripherals(..))
 import Peripherals.Teardown(teardownPeripherals)
 import Clash.Prelude
-import Machine(
-  Machine(..),
+import Bus(Peripherals(..))
+import Cpu(
   RISCVCPU(..),
-  Peripherals(..),
-  machineInit, RISCVCPU (RISCVCPU))
+  RISCVCPU (RISCVCPU),
+  riscvCPUInit)
 import Fetch(fetchInstruction, FetchResult (Instruction, Misaligned))
 import Isa.Decode(decode)
 
@@ -27,6 +27,11 @@ data Simulation
   = Success [Machine]
   | Failure String
   deriving (Show)
+data Machine = Machine
+  { cpu :: RISCVCPU,
+    peripherals :: Peripherals
+  }
+  deriving (Generic, Show, Eq, NFDataX)
 
 -- machine :: Machine
 -- machine = machineInit
@@ -69,7 +74,11 @@ simulation args = do
     InitializationError e -> return $ Failure e
     InitializedPeripherals ram -> do
 
-      let initState = machineInit $ Machine.Peripherals ram
+      let initState =
+            Machine {
+              cpu = riscvCPUInit,
+              peripherals = Bus.Peripherals ram
+              }
       sim <- simulationLoop 15 initState
       teardownPeripherals
       return $ Success sim
diff --git a/rv_formal.cabal b/rv_formal.cabal
index 6b3c195..d2840c6 100644
--- a/rv_formal.cabal
+++ b/rv_formal.cabal
@@ -97,7 +97,7 @@ library
     Types,
     Bus,
     BusTypes,
-    Machine,
+    Cpu,
     RegFiles,
     Fetch,
     Util