diff --git a/src/ast.ml b/src/ast.ml
index fe087cf..c2fb0da 100644
--- a/src/ast.ml
+++ b/src/ast.ml
@@ -73,3 +73,7 @@ and t_node =
 
 type t_nodelist = t_node list
 
+type t_ck = base_ck list
+and base_ck = 
+    | Base
+    | On of base_ck * t_expression
diff --git a/src/main.ml b/src/main.ml
index 3652564..e4e38b8 100644
--- a/src/main.ml
+++ b/src/main.ml
@@ -25,7 +25,7 @@ let exec_passes ast main_fn verbose debug passes f =
 
 let _ =
   (** Usage and argument parsing. *)
-	let default_passes = ["automata_validity" ;"automata_translation"; "linearization"; "pre2vars"; "equations_ordering"] in
+  let default_passes = ["automata_validity" ;"automata_translation"; "linearization"; "pre2vars"; "equations_ordering"; "clock_unification"] in
   let sanity_passes = ["chkvar_init_unicity"; "check_typing"] in
   let usage_msg =
     "Usage: main [-passes p1,...,pn] [-ast] [-verbose] [-debug] \
@@ -68,10 +68,11 @@ let _ =
       ("pre2vars", Passes.pre2vars);
       ("chkvar_init_unicity", Passes.chkvar_init_unicity);
       ("automata_translation", Passes.automata_translation_pass);
-	  ("automata_validity", Passes.check_automata_validity);
+      ("automata_validity", Passes.check_automata_validity);
       ("linearization", Passes.pass_linearization);
       ("equations_ordering", Passes.pass_eq_reordering);
       ("check_typing", Passes.pass_typing);
+      ("clock_unification", Passes.clock_unification_pass);
     ];
 
   (** Main functionality below *)
diff --git a/src/passes.ml b/src/passes.ml
index e8879d1..02b1501 100644
--- a/src/passes.ml
+++ b/src/passes.ml
@@ -89,7 +89,7 @@ let chkvar_init_unicity verbose debug main_fn : t_nodelist -> t_nodelist option
   let aux (node: t_node) : t_node option =
     let incr_aux h n =
       match Hashtbl.find_opt h n with
-      | None -> failwith "todo, should not happened."
+      | None -> raise (PassExn "todo, should not happened.")
       | Some num -> Hashtbl.replace h n (num + 1)
       in
     let incr_eq h (((_, patt), _): t_equation) =
@@ -403,7 +403,7 @@ let check_automata_validity verbos debug main_fn =
     match init with | State(name, eqs, cond, next) -> init_left_side eqs;
     let validity = List.for_all (fun s -> (check_state s)) states in
     if not validity then
-      failwith "Automaton branch has different variables assignment in different branches"
+      raise (PassExn "Automaton branch has different variables assignment in different branches")
     end
   in
   let aux node = 
@@ -479,8 +479,21 @@ let automaton_translation debug automaton =
         )
     in
 
-  let rec translate_var s v explist = match explist with
-  | [] -> EConst([TInt], CInt(0)) (* TODO *)
+  let default_constant ty =
+    let defaults ty = match ty with
+    | TInt  -> EConst([ty], CInt(0))
+    | TBool -> EConst([ty], CBool(false))
+    | TReal -> EConst([ty], CReal(0.0))
+    in
+    match ty with
+    | [TInt]  -> EConst(ty, CInt(0))
+    | [TBool] -> EConst(ty, CBool(false))
+    | [TReal] -> EConst(ty, CReal(0.0))
+    | _ -> ETuple(ty, List.map defaults ty)
+  in
+
+  let rec translate_var s v explist ty = match explist with
+  | [] -> default_constant ty (* TODO *)
   | (state, exp)::q -> 
       ETriOp(Utils.type_exp exp, TOp_if,
         EComp([TBool], COp_eq, 
@@ -488,7 +501,7 @@ let automaton_translation debug automaton =
           EConst([TInt], CInt(Hashtbl.find state_to_int state))
         ),
         exp,
-        translate_var s v q
+        translate_var s v q ty
       )
   in
 
@@ -501,7 +514,7 @@ let automaton_translation debug automaton =
   init_state_translation states 1;
   let exp_transition = EBinOp([TInt], BOp_arrow, EConst([TInt], CInt(1)), EMonOp([TInt], MOp_pre, transition_eq states s)) in
   let new_equations = [(([TInt], [IVar(s)]), exp_transition)] in
-  Hashtbl.fold (fun var explist acc -> (var, translate_var s var explist)::acc) gathered new_equations, IVar(s)
+  Hashtbl.fold (fun var explist acc -> (var, translate_var s var explist (fst var))::acc) gathered new_equations, IVar(s)
 
 
 let automata_trans_pass debug (node:t_node) : t_node option=
@@ -529,4 +542,106 @@ let automata_trans_pass debug (node:t_node) : t_node option=
 let automata_translation_pass verbose debug main_fn = 
   node_pass (automata_trans_pass debug)
 
+let clock_unification_pass verbose debug main_fn ast = 
 
+  let failure str = raise (PassExn ("Failed to unify clocks: "^str)) in
+    
+  let known_clocks = Hashtbl.create 100 in
+
+  let find_clock_var var = 
+      match Hashtbl.find_opt known_clocks var with
+      | None -> 
+        begin
+          match var with
+          | BVar(name)
+          | IVar(name)
+          | RVar(name) -> raise (PassExn ("Cannot find clock of variable "^name) )
+        end
+      | Some c -> c
+  in
+
+  let rec compute_clock_exp exp = match exp with
+  | EConst(_, _) -> [Base]
+  | EVar(_, var) -> find_clock_var var
+  | EMonOp(_, MOp_pre, _) -> [Base]
+  | EMonOp(_, _, e) -> compute_clock_exp e
+
+  | EComp(_, _, e1, e2)
+  | EReset(_, e1, e2)
+  | EBinOp(_, _, e1, e2) -> 
+    begin
+      let c1 = compute_clock_exp e1
+      and c2 = compute_clock_exp e2 in
+      if c1 <> c2 then
+        failure "Binop"
+      else
+        c1
+    end
+  | EWhen(_, e1, e2) -> 
+      begin
+        match compute_clock_exp e1 with
+        | [c1] -> [On (c1, e2)]
+        | _ -> failure "When"
+      end
+  | ETriOp(_, TOp_merge, e1, e2, e3) ->
+    begin
+      let c1 = compute_clock_exp e1
+      and c2 = compute_clock_exp e2
+      and c3 = compute_clock_exp e3 in
+      match c1, c2, c3 with
+      | [c1], [On(cl2, e2)], [On(cl3, e3)] ->
+          begin
+            if cl2 <> c1 || cl3 <> c1 then
+              failure "Triop clocks"
+            else match e2, e3 with
+            | EMonOp(_, MOp_not, e), _ when e = e3 -> [c1]
+            | _, EMonOp(_, MOp_not, e) when e = e2 -> [c1]
+            | _ -> failure "Triop condition"
+          end
+      | _ -> failure ("Merge format")
+    end
+  | ETriOp(_, TOp_if, e1, e2, e3) ->
+      let c1 = compute_clock_exp e1
+      and c2 = compute_clock_exp e2
+      and c3 = compute_clock_exp e3 in
+      if c2 <> c3 then
+        failure "If clocks"
+      else c2
+
+  | ETuple(_, explist) -> List.concat_map compute_clock_exp explist
+  | EApp(_, node, e) -> 
+      let rec aux_app clk_list = match clk_list with
+      | [] -> raise (PassExn "Node called with no argument provided")
+      | [cl] -> cl
+      | t::q -> if t = (aux_app q) then t else failure "App diff clocks"
+      and mult_clk cl out_list = match out_list with
+      | [] -> []
+      | t::q -> cl::(mult_clk cl q)
+      in
+      mult_clk (aux_app (compute_clock_exp e)) (snd node.n_outputs)
+      in
+
+  let rec compute_eq_clock eq = 
+    let rec step vars clks = match vars, clks with
+    | [], [] -> ()
+    | [], c::q -> raise (PassExn "Mismatch between clock size")
+    | v::t, c::q -> Hashtbl.replace known_clocks v [c]; step t q
+    | l, [] -> raise (PassExn "Mismatch between clock size")
+    in
+    let (_, vars), exp = eq in
+    let clk = compute_clock_exp exp in
+    step vars clk
+  in
+
+  let compute_clock_node n = 
+    begin
+      Hashtbl.clear known_clocks;
+      List.iter (fun v -> Hashtbl.replace known_clocks v [Base]) (
+        snd n.n_inputs); (* Initializing inputs to base clock *)
+      List.iter compute_eq_clock n.n_equations;
+      if not (List.for_all (fun v -> (Hashtbl.find known_clocks v) = [Base]) (
+        snd n.n_outputs)) then failure "Outputs" (*Checking that the node's output are on base clock *)
+      else
+        Some n
+    end
+  in node_pass compute_clock_node ast