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bus: ASMI hub (untested)

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1 parent c1bff38 commit 945d655d451f513095a1ea3cb603b7ebe97b3b89 @sbourdeauducq sbourdeauducq committed Feb 10, 2012
Showing with 140 additions and 0 deletions.
  1. +140 −0 migen/bus/asmibus.py
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+from migen.fhdl.structure import *
+
+class FinalizeError(Exception):
+ pass
+
+(SLOT_EMPTY, SLOT_PENDING, SLOT_PROCESSING) = range(3)
+
+class Slot:
+ def __init__(self, aw, time):
+ self.state = Signal(BV(2))
+ self.we = Signal()
+ self.adr = Signal(BV(aw))
+ self.time = time
+ if self.time:
+ self._counter = Signal(BV(bits_for(time)))
+ self.mature = Signal()
+
+ self.allocate = Signal()
+ self.allocate_we = Signal()
+ self.allocate_adr = Signal(BV(aw))
+ self.process = Signal()
+ self.call = Signal()
+
+ def get_fragment(self):
+ comb = []
+ sync = [
+ If(self.allocate,
+ self.state.eq(SLOT_PENDING)
+ self.we.eq(self.allocate_we),
+ self.adr.eq(self.allocate_adr)
+ ),
+ If(self.process, self.state.eq(SLOT_PROCESSING)),
+ If(self.call, self.state.eq(SLOT_EMPTY))
+ ]
+ if self.time:
+ comb += [
+ self.mature.eq(self._counter == 0)
+ ]
+ sync += [
+ If(self.allocate,
+ self._counter.eq(self.time)
+ ).Elif(self._counter.eq != 0,
+ self._counter.eq(self._counter - 1)
+ )
+ ]
+ return Fragment(comb, sync)
+
+class Port:
+ def __init__(self, hub, nslots):
+ self.hub = hub
+ self.slots = [Slot(self.hub.aw, self.hub.time) for i in range(nslots)]
+ self.finalized = False
+
+ # request issuance
+ self.adr = Signal(BV(self.hub.aw))
+ self.we = Signal()
+ self.stb = Signal()
+ # tag_issue is created by finalize()
+ self.ack = Signal()
+
+ # request completion
+ self.call = Signal()
+ # tag_call is created by finalize()
+ self.dat_r = Signal(BV(self.hub.dw))
+ self.dat_w = Signal(BV(self.hub.dw))
+ self.dat_wm = Signal(BV(self.hub.dw//8))
+
+ def finalize(self, tagbits, base):
+ if self.finalized:
+ raise FinalizeError
+ self.tagbits = tagbits
+ self.base = base
+ nslots = len(self.slots)
+ if nslots > 1:
+ self.tag_issue = Signal(BV(bits_for(nslots-1)))
+ self.tag_call = Signal(BV(tagbits))
+
+ def get_call_expression(self, slotn=0):
+ if not self.finalized:
+ raise FinalizeError
+ return self.call \
+ && (self.tag_call == Constant(self.base + slotn, BV(self.tagbits)))
+
+ def get_fragment(self):
+ if not self.finalized:
+ raise FinalizeError
+
+ slots_fragment = sum([s.get_fragment() for s in self.slots], Fragment())
+
+ comb = []
+ sync = []
+
+ # allocate
+ for s in self.slots:
+ comb += [
+ s.allocate_we.eq(self.we),
+ s.allocate_adr.eq(self.adr)
+ ]
+ choose_slot = None
+ for s in reversed(self.slots):
+ choose_slot = If(s.state == SLOT_EMPTY,
+ self.ack.eq(1),
+ s.allocate.eq(self.stb)
+ ).Else(choose_slot)
+ comb.append(choose_slot)
+
+ # call
+ comb += [s.call.eq(self.get_call_expression(n))
+ for n, s in enumerate(self.slots)]
+
+ return slots_fragment + Fragment(comb, sync)
+
+class Hub:
+ def __init__(self, aw, dw, time=0):
+ self.aw = aw
+ self.dw = dw
+ self.time = time
+ self.ports = []
+ self.finalized = False
+
+ def get_port(self, nslots=1):
+ if self.finalized:
+ raise FinalizeError
+ self.ports.append(Port(self, nslots))
+
+ def finalize(self):
+ if self.finalized:
+ raise FinalizeError
+ self.finalized = True
+ nslots = sum([len(port.slots) for port in self.ports])
+ tagbits = bits_for(nslots-1)
+ base = 0
+ for port in self.ports:
+ port.finalize(tagbits, base)
+ base += len(port.slots)
+
+ def get_fragment(self):
+ if not self.finalized:
+ raise FinalizeError
+ return sum([port.get_fragment() for port in self.ports])

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