diff --git a/examples/divider_conv.py b/examples/divider_conv.py
index 0531ad42e..988e0b8a6 100644
--- a/examples/divider_conv.py
+++ b/examples/divider_conv.py
@@ -46,5 +46,5 @@ class Divider:
 
 d = Divider(32)
 f = d.GetFragment()
-o = verilog.Convert(f, {d.start_i, d.dividend_i, d.divisor_i}, {d.ready_o, d.quotient_o, d.remainder_o})
+o = verilog.Convert(f, {d.ready_o, d.quotient_o, d.remainder_o}, {d.start_i, d.dividend_i, d.divisor_i})
 print(o)
\ No newline at end of file
diff --git a/examples/simple_gpio.py b/examples/simple_gpio.py
new file mode 100644
index 000000000..2215a8164
--- /dev/null
+++ b/examples/simple_gpio.py
@@ -0,0 +1,25 @@
+from migen.fhdl import structure as f
+from migen.fhdl import verilog
+from migen.bank import description, csrgen
+
+ninputs = 4
+noutputs = 4
+
+oreg = description.Register("o")
+ofield = description.Field(oreg, "val", noutputs)
+ireg = description.Register("i")
+ifield = description.Field(ireg, "val", ninputs, description.READ_ONLY, description.WRITE_ONLY)
+
+# input path
+gpio_in = f.Signal(f.BV(ninputs), name="gpio_in")
+gpio_in_s = f.Signal(f.BV(ninputs), name="gpio_in_s") # synchronizer
+incomb = [f.Assign(ifield.dev_we, 1)]
+insync = [f.Assign(gpio_in_s, gpio_in), f.Assign(ifield.dev_w, gpio_in_s)]
+inf = f.Fragment(incomb, insync)
+
+bank = csrgen.Bank([oreg, ireg])
+f = bank.GetFragment() + inf
+i = bank.interface
+ofield.dev_r.name = "gpio_out"
+v = verilog.Convert(f, {i.d_o, ofield.dev_r}, {i.a_i, i.we_i, i.d_i, gpio_in})
+print(v)
\ No newline at end of file
diff --git a/migen/bank/csrgen.py b/migen/bank/csrgen.py
new file mode 100644
index 000000000..e605415b1
--- /dev/null
+++ b/migen/bank/csrgen.py
@@ -0,0 +1,72 @@
+from ..fhdl import structure as f
+from ..bus.csr import *
+from .description import *
+from functools import partial
+
+class Bank:
+	def __init__(self, description, address=0):
+		self.description = description
+		self.address = address
+		self.interface = Slave()
+		d = partial(f.Declare, self)
+		d("_sel")
+	
+	def GetFragment(self):
+		a = f.Assign
+		comb = []
+		sync = []
+		
+		comb.append(a(self._sel, self.interface.a_i[12:] == f.Constant(self.address, f.BV(4))))
+		
+		nregs = len(self.description)
+		nbits = f.BitsFor(nregs-1)
+		
+		# Bus writes
+		bwcases = []
+		for i in range(nregs):
+			reg = self.description[i]
+			nfields = len(reg.fields)
+			bwra = []
+			for j in range(nfields):
+				field = reg.fields[j]
+				if field.access_bus == WRITE_ONLY or field.access_bus == READ_WRITE:
+					bwra.append(a(field.storage, self.interface.d_i[j]))
+			if bwra:
+				bwcases.append((f.Constant(i, f.BV(nbits)), bwra))
+		if bwcases:
+			sync.append(f.If(self._sel & self.interface.we_i, [f.Case(self.interface.a_i[:nbits], bwcases)]))
+		
+		# Bus reads
+		brcases = []
+		for i in range(nregs):
+			reg = self.description[i]
+			nfields = len(reg.fields)
+			brs = []
+			reg_readable = False
+			for j in range(nfields):
+				field = reg.fields[j]
+				if field.access_bus == READ_ONLY or field.access_bus == READ_WRITE:
+					brs.append(field.storage)
+					reg_readable = True
+				else:
+					brs.append(f.Constant(0, f.bv(field.size)))
+			if reg_readable:
+				if len(brs) > 1:
+					brcases.append((f.Constant(i, f.BV(nbits)), [a(self.interface.d_o, f.Cat(*brs))]))
+				else:
+					brcases.append((f.Constant(i, f.BV(nbits)), [a(self.interface.d_o, brs[0])]))
+		if brcases:
+			sync.append(a(self.interface.d_o, f.Constant(0, f.BV(32))))
+			sync.append(f.If(self._sel, [f.Case(self.interface.a_i[:nbits], brcases)]))
+		else:
+			comb.append(a(self.interface.d_o, f.Constant(0, f.BV(32))))
+		
+		# Device access
+		for reg in self.description:
+			for field in reg.fields:
+				if field.access_dev == READ_ONLY or field.access_dev == READ_WRITE:
+					comb.append(a(field.dev_r, field.storage))
+				if field.access_dev == WRITE_ONLY or field.access_dev == READ_WRITE:
+					sync.append(f.If(field.dev_we, [a(field.storage, field.dev_w)]))
+		
+		return f.Fragment(comb, sync)
\ No newline at end of file
diff --git a/migen/bank/description.py b/migen/bank/description.py
new file mode 100644
index 000000000..accb18232
--- /dev/null
+++ b/migen/bank/description.py
@@ -0,0 +1,28 @@
+from ..fhdl import structure as f
+
+class Register:
+	def __init__(self, name):
+		self.name = name
+		self.fields = []
+	
+	def AddField(self, f):
+		self.fields.append(f)
+
+(READ_ONLY, WRITE_ONLY, READ_WRITE) = range(3)
+
+class Field:
+	def __init__(self, parent, name, size=1, access_bus=READ_WRITE, access_dev=READ_ONLY, reset=0):
+		self.parent = parent
+		self.name = name
+		self.size = size
+		self.access_bus = access_bus
+		self.access_dev = access_dev
+		self.reset = reset
+		fullname = parent.name + "_" + name
+		self.storage = f.Signal(f.BV(self.size), fullname)
+		if self.access_dev == READ_ONLY or self.access_dev == READ_WRITE:
+			self.dev_r = f.Signal(f.BV(self.size), fullname + "_r")
+		if self.access_dev == WRITE_ONLY or self.access_dev == READ_WRITE:
+			self.dev_w = f.Signal(f.BV(self.size), fullname + "_w")
+			self.dev_we = f.Signal(name=fullname + "_we")
+		self.parent.AddField(self)
\ No newline at end of file
diff --git a/migen/fhdl/convtools.py b/migen/fhdl/convtools.py
index df2855b7e..bb71ed4fc 100644
--- a/migen/fhdl/convtools.py
+++ b/migen/fhdl/convtools.py
@@ -44,6 +44,9 @@ def ListSignals(node):
 		return set().union(*l)
 	elif isinstance(node, If):
 		return ListSignals(node.cond) | ListSignals(node.t) | ListSignals(node.f)
+	elif isinstance(node, Case):
+		l = list(map(lambda x: ListSignals(x[1]), node.cases))
+		return ListSignals(node.test).union(*l).union(ListSignals(node.default))
 	elif isinstance(node, Fragment):
 		return ListSignals(node.comb) | ListSignals(node.sync)
 	else:
@@ -64,6 +67,9 @@ def ListTargets(node):
 		return set().union(*l)
 	elif isinstance(node, If):
 		return ListTargets(node.t) | ListTargets(node.f)
+	elif isinstance(node, Case):
+		l = list(map(lambda x: ListTargets(x[1]), node.cases))
+		return ListTargets(node.default).union(*l)
 	else:
 		raise TypeError
 
@@ -73,4 +79,4 @@ def InsertReset(rst, sl):
 	for t in targets:
 		if not t.variable:
 			resetcode.append(Assign(t, t.reset))
-	return If(rst == 1, resetcode, sl)
\ No newline at end of file
+	return If(rst, resetcode, sl)
\ No newline at end of file
diff --git a/migen/fhdl/structure.py b/migen/fhdl/structure.py
index db37eee7f..8e924b4b2 100644
--- a/migen/fhdl/structure.py
+++ b/migen/fhdl/structure.py
@@ -195,9 +195,10 @@ class If:
 		return r
 
 class Case:
-	def __init__(self, test, cases=[]):
+	def __init__(self, test, cases=[], default=StatementList()):
 		self.test = test
-		self.cases = cases
+		self.cases = [(c[0], _sl(c[1])) for c in cases]
+		self.default = _sl(default)
 
 #
 
@@ -207,4 +208,7 @@ class Fragment:
 		self.sync = _sl(sync)
 	
 	def __str__(self):
-		return "Comb:\n" + _indent(str(self.comb)) + "\nSync:\n" + _indent(str(self.sync))
\ No newline at end of file
+		return "Comb:\n" + _indent(str(self.comb)) + "\nSync:\n" + _indent(str(self.sync))
+	
+	def __add__(self, other):
+		return Fragment(self.comb.l + other.comb.l, self.sync.l + other.sync.l)
\ No newline at end of file
diff --git a/migen/fhdl/verilog.py b/migen/fhdl/verilog.py
index e5acfd1e2..d3e291a4b 100644
--- a/migen/fhdl/verilog.py
+++ b/migen/fhdl/verilog.py
@@ -2,7 +2,7 @@ from .structure import *
 from .convtools import *
 from functools import partial
 
-def Convert(f, ins, outs, name="top", clkname="sys_clk", rstname="sys_rst"):
+def Convert(f, outs=set(), ins=set(), name="top", clkname="sys_clk", rstname="sys_rst"):
 	ns = Namespace()
 	
 	clks = Signal(name=clkname)
@@ -50,13 +50,21 @@ def Convert(f, ins, outs, name="top", clkname="sys_clk", rstname="sys_rst"):
 		elif isinstance(node, StatementList):
 			return "".join(list(map(partial(printnode, level), node.l)))
 		elif isinstance(node, If):
-			r = "\t"*level + "if " + printnode(level, node.cond) + " begin\n"
+			r = "\t"*level + "if (" + printnode(level, node.cond) + ") begin\n"
 			r += printnode(level + 1, node.t)
 			if node.f.l:
 				r += "\t"*level + "end else begin\n"
 				r += printnode(level + 1, node.f)
 			r += "\t"*level + "end\n"
 			return r
+		elif isinstance(node, Case):
+			r = "\t"*level + "case (" + printnode(level, node.test) + ")\n"
+			for case in node.cases:
+				r += "\t"*(level + 1) + printnode(level, case[0]) + ": begin\n"
+				r += printnode(level + 2, case[1])
+				r += "\t"*(level + 1) + "end\n"
+			r += "\t"*level + "endcase\n"
+			return r
 		else:
 			raise TypeError