actorlib/misc/IntSequence: add offset feature

diff --git a/migen/actorlib/misc.py b/migen/actorlib/misc.py
index 60b18ac1355c9230de12f82ceb8c6714238ac743..1c6a3c79b335b6440c4bae9334783301b336b270 100644 (file)
--- a/migen/actorlib/misc.py
+++ b/migen/actorlib/misc.py
@@ -5,13 +5,18 @@ from migen.flow.actor import *
 
 # Generates integers from start to maximum-1
 class IntSequence(Actor):
-       def __init__(self, nbits, step=1):
+       def __init__(self, nbits, offsetbits=0, step=1):
                self.nbits = nbits
+               self.offsetbits = offsetbits
                self.step = step
                
+               parameters_layout = [("maximum", BV(self.nbits))]
+               if self.offsetbits:
+                       parameters_layout.append(("offset", BV(self.offsetbits)))
+               
                super().__init__(
-                       ("maximum", Sink, [("value", BV(nbits))]),
-                       ("source", Source, [("value", BV(nbits))]))
+                       ("parameters", Sink, parameters_layout),
+                       ("source", Source, [("value", BV(max(self.nbits, self.offsetbits)))]))
        
        def get_fragment(self):
                load = Signal()
@@ -19,6 +24,8 @@ class IntSequence(Actor):
                last = Signal()
                
                maximum = Signal(BV(self.nbits))
+               if self.offsetbits:
+                       offset = Signal(BV(self.offsetbits))
                counter = Signal(BV(self.nbits))
                
                if self.step > 1:
@@ -28,7 +35,8 @@ class IntSequence(Actor):
                sync = [
                        If(load,
                                counter.eq(0),
-                               maximum.eq(self.token("maximum").value)
+                               maximum.eq(self.token("parameters").maximum),
+                               offset.eq(self.token("parameters").offset) if self.offsetbits else None
                        ).Elif(ce,
                                If(last,
                                        counter.eq(0)
@@ -37,14 +45,17 @@ class IntSequence(Actor):
                                )
                        )
                ]
-               comb.append(self.token("source").value.eq(counter))
+               if self.offsetbits:
+                       comb.append(self.token("source").value.eq(counter + offset))
+               else:
+                       comb.append(self.token("source").value.eq(counter))
                counter_fragment = Fragment(comb, sync)
                
                fsm = FSM("IDLE", "ACTIVE")
                fsm.act(fsm.IDLE,
                        load.eq(1),
-                       self.endpoints["maximum"].ack.eq(1),
-                       If(self.endpoints["maximum"].stb, fsm.next_state(fsm.ACTIVE))
+                       self.endpoints["parameters"].ack.eq(1),
+                       If(self.endpoints["parameters"].stb, fsm.next_state(fsm.ACTIVE))
                )
                fsm.act(fsm.ACTIVE,
                        self.busy.eq(1),