--- nand.py-
+++ nand.py
@@ -42,26 +42,6 @@
 		elif self.parent and hasattr(self.parent, 'update'):
 			self.enque(self.parent.update)
 
-class Foo(Obj):
-	def __init__(self, parent, latency=None):
-		Obj.__init__(self, parent, 'foo', latency)
-		self.v = 0
-
-		Pin(self, 'inp')
-		Pin(self, 'out')
-
-		self.enque( self.add, (0, ) )
-
-	def add(self, a):
-		self.v += a
-		self.dbgout( 'v={}'.format(self.v) )
-		if self.v < 55:
-			self.enque( self.add, (a+1,) )
-
-	def update(self):
-		v = not self.inp.v
-		self.enque( self.out.set, (v,) )
-
 class NAND(Obj):
 	def __init__(self, parent, name='nand', latency=10):
 		Obj.__init__(self, parent, name, latency)
@@ -98,8 +78,10 @@
 	def __init__(self, parent, name='not_', latency=10):
 		Obj.__init__(self, parent, name)
 		NAND(self, 'nand', latency)
-		Pin(self, 'inp').conn = self.nand.inp_a
-		Pin(self, 'H', 'H').conn = self.nand.inp_b
+		Joint(self, 'jt')
+		Pin(self, 'inp').conn = self.jt.new_pin()
+		self.jt.new_pin().conn = self.nand.inp_a
+		self.jt.new_pin().conn = self.nand.inp_b
 		self.nand.out.conn = Pin(self, 'out')
 
 class AND(Obj):
@@ -161,6 +143,20 @@
 		self.nand_b.out.conn = self.nand_o.inp_b
 		self.nand_o.out.conn = Pin(self, 'out')
 
+class CLK(Obj):
+	def __init__(self, parent, hz=1.0, name='clk'):
+		Obj.__init__(self, parent, name)
+		latency = tm_from_fsec( 1.0 / ( 2 * hz ) )
+		NAND(self, 'nand', latency)
+		Joint(self)
+		NOT(self)
+
+		Pin(self, 'en', 'L').conn = self.nand.inp_a
+		self.nand.out.conn = self.jt.new_pin()
+		self.jt.new_pin().conn = self.nand.inp_b
+		self.jt.new_pin().conn = self.not_.inp
+		self.not_.out.conn = Pin(self, 'out')
+
 class Lamp(Obj):
 	def __init__(self, parent, name='lamp', latency=None):
 		Obj.__init__(self, parent, name, latency)
@@ -197,12 +193,15 @@
 
 	def main_loop(self):
 		self.run = True
+		start = time.time()
 		while self.run:
 			cmd_exec( sys.stdin )
 			if self.que:
 				#dbgout( 'que={}'.format(self.que) )
 				(tm, f, args) = self.que.pop(0)
 				self.now = tm
+				if '-f' not in sys.argv:
+					tm_sleep(tm, start)
 				f(*args)
 			else:
 				time.sleep(0.5)
@@ -234,7 +233,6 @@
 	return n1 > n2 if s1 == s2 else s1 > s2
 
 def tm_add( (s1,n1), (s2,n2) ):
-	giga = 1000000000
 	n1 += n2
 	s1 += s2 + n1 / giga
 	n1 %= giga
@@ -243,11 +241,26 @@
 def tm_str( (s,n) ):
 	return '{}.{:0>9}'.format(s, n)
 
+def tm_sleep( tm, start_fsec ):
+	wait = start_fsec + tm_fsec(tm) - time.time()
+	if wait > 0:
+		time.sleep(wait)
+
+def tm_fsec( (s, n) ):
+	return s + float(n) / giga
+	
+def tm_from_fsec(fsec):
+	s = int(fsec)
+	n = int( (fsec - s) * giga )
+	return (s, n)
+
 def dbgout(s, always=False):
 	if always or '-v' in sys.argv:
 		print '{} {}'.format( tm_str(sched.now), s )
 		sys.stdout.flush()
 
+giga = 1000000000
+
 if __name__ == "__main__":
 	sched = Sched()