litex/migen/actorlib/control.py

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from migen.fhdl.structure import *
from migen.corelogic.record import *
from migen.corelogic.fsm import *
from migen.flow.actor import *
# Generates integers from start to maximum-1
class For(Actor):
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def __init__(self, nbits, step=1):
self.nbits = nbits
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self.step = step
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super().__init__(
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("maximum", Sink, [("value", BV(nbits))]),
("source", Source, [("value", BV(nbits))]))
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def get_fragment(self):
load = Signal()
ce = Signal()
last = Signal()
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maximum = Signal(BV(self.nbits))
counter = Signal(BV(self.nbits))
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if self.step > 1:
comb = [last.eq(counter + self.step >= maximum)]
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else:
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comb = [last.eq(counter + 1 == maximum)]
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sync = [
If(load,
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counter.eq(0),
maximum.eq(self.token("maximum").value)
).Elif(ce,
If(last,
counter.eq(0)
).Else(
counter.eq(counter + self.step)
)
)
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]
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comb.append(self.token("source").value.eq(counter))
counter_fragment = Fragment(comb, sync)
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fsm = FSM("IDLE", "ACTIVE")
fsm.act(fsm.IDLE,
load.eq(1),
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self.endpoints["maximum"].ack.eq(1),
If(self.endpoints["maximum"].stb, fsm.next_state(fsm.ACTIVE))
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)
fsm.act(fsm.ACTIVE,
self.busy.eq(1),
self.endpoints["source"].stb.eq(1),
If(self.endpoints["source"].ack,
ce.eq(1),
If(last, fsm.next_state(fsm.IDLE))
)
)
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return counter_fragment + fsm.get_fragment()