bus: memory initiator

migen/bus/memory.py

@@ -0,0 +1,36 @@
+from migen.bus.transactions import *
+from migen.sim.generic import PureSimulable
+
+def _byte_mask(orig, dat_w, sel):
+	r = 0
+	shift = 0
+	while sel:
+		if sel & 1:
+			r |= (dat_w & 0xff) << shift
+		else:
+			r |= (orig & 0xff) << shift
+		orig >>= 8
+		dat_w >>= 8
+		sel >>= 1
+		shift += 8
+	return r
+
+class Initiator(PureSimulable):
+	def __init__(self, generator, mem):
+		self.generator = generator
+		self.mem = mem
+		self.done = False
+
+	def do_simulation(self, s):
+		if not self.done:
+			try:
+				transaction = next(self.generator)
+			except StopIteration:
+				self.done = True
+				transaction = None
+			if isinstance(transaction, TRead):
+				transaction.data = s.rd(self.mem, transaction.address)
+			elif isinstance(transaction, TWrite):
+				d = s.rd(self.mem, transaction.address)
+				d_mask = _byte_mask(d, transaction.data, transaction.sel)
+				s.wr(s.mem, d_mask, transaction.address)