Remove the empty state of the alu function.

[matthijs/master-project/cλash.git] / Alu.hs

diff --git a/Alu.hs b/Alu.hs
index 2495df25f0c80b885f4095012088e4f2b30f2623..b888fc9dca18419523a4b33234c6e8e900d083ac 100644 (file)
--- a/Alu.hs
+++ b/Alu.hs
@@ -14,57 +14,59 @@ program = [
             (High, High, DontCare) -- r1 = z (0)
           ]
 
-initial_state = ((Low, High), (), Low, Low)
+initial_state = (Regs Low High, Low, Low)
 
---
---
+-- Register bank
 
 type RegAddr = Bit
-type RegisterBankState = (Bit, Bit)
+--type RegisterBankState = (Bit, Bit)
+data RegisterBankState = Regs { r0, r1 :: Bit} deriving (Show)
+
 register_bank :: 
   (RegAddr, Bit, Bit) -> -- (addr, we, d)
   RegisterBankState -> -- s
   (RegisterBankState, Bit) -- (s', o)
 
 register_bank (Low, Low, _) s = -- Read r0
-  (s, fst s)
+  (s, r0 s)
 
 register_bank (High, Low, _) s = -- Read r1
-  (s, snd s)
+  (s, r1 s)
 
 register_bank (addr, High, d) s = -- Write
   (s', DontCare)
   where
-    (r0, r1) = s
+    Regs r0 r1 = s
     r0' = if addr == Low then d else r0
     r1' = if addr == High then d else r1
-    s' = (r0', r1')
+    s' = Regs r0' r1'
+
+-- ALU
 
-type AluState = ()
 type AluOp = Bit
 
-alu :: (AluOp, Bit, Bit) -> AluState -> (AluState, Bit)
-alu (High, a, b) s = ((), a `hwand` b)
-alu (Low, a, b) s = ((), a `hwor` b)
+alu :: (AluOp, Bit, Bit) -> Bit
+alu (High, a, b) = a `hwand` b
+alu (Low, a, b) = a `hwor` b
 
-type ExecState = (RegisterBankState, AluState, Bit, Bit)
+type ExecState = (RegisterBankState, Bit, Bit)
 exec :: (RegAddr, Bit, AluOp) -> ExecState -> (ExecState, ())
 
 -- Read & Exec
 exec (addr, Low, op) s =
   (s', ())
   where
-    (reg_s, alu_s, t, z) = s
+    (reg_s, t, z) = s
     (reg_s', t') = register_bank (addr, Low, DontCare) reg_s
-    (alu_s', z') = alu (op, t', t) alu_s
-    s' = (reg_s', alu_s', t', z')
+    z' = alu (op, t', t)
+    s' = (reg_s', t', z')
 
 -- Write
 exec (addr, High, op) s =
   (s', ())
   where
-    (reg_s, alu_s, t, z) = s
+    (reg_s, t, z) = s
     (reg_s', _) = register_bank (addr, High, z) reg_s
-    s' = (reg_s', alu_s, t, z)
+    s' = (reg_s', t, z)
 
 -- vim: set ts=8 sw=2 sts=2 expandtab: