39 lines
841 B
Python
39 lines
841 B
Python
from migen.fhdl.std import *
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(SP_WITHDRAW, SP_CE) = range(2)
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class RoundRobin(Module):
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def __init__(self, n, switch_policy=SP_WITHDRAW):
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self.request = Signal(n)
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self.grant = Signal(max=n)
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self.switch_policy = switch_policy
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if self.switch_policy == SP_CE:
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self.ce = Signal()
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###
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if n > 1:
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cases = {}
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for i in range(n):
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switch = []
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for j in reversed(range(i+1,i+n)):
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t = j % n
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switch = [
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If(self.request[t],
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self.grant.eq(t)
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).Else(
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*switch
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)
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]
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if self.switch_policy == SP_WITHDRAW:
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case = [If(~self.request[i], *switch)]
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else:
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case = switch
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cases[i] = case
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statement = Case(self.grant, cases)
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if self.switch_policy == SP_CE:
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statement = If(self.ce, statement)
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self.sync += statement
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else:
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self.comb += self.grant.eq(0)
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