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https://github.com/myhdl/myhdl.git
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96 lines
2.1 KiB
Python
96 lines
2.1 KiB
Python
import myhdl
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from myhdl import *
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ACTIVE_LOW = 0
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FRAME_SIZE = 8
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t_State = enum('SEARCH', 'CONFIRM', 'SYNC')
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@block
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def FramerCtrl(SOF, state, syncFlag, clk, reset_n):
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""" Framing control FSM.
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SOF -- start-of-frame output bit
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state -- FramerState output
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syncFlag -- sync pattern found indication input
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clk -- clock input
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reset_n -- active low reset
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"""
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index = Signal(0) # position in frame
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@always(clk.posedge, reset_n.negedge)
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def FSM():
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if reset_n == ACTIVE_LOW:
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SOF.next = 0
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index.next = 0
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state.next = t_State.SEARCH
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else:
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index.next = (index + 1) % FRAME_SIZE
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SOF.next = 0
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if state == t_State.SEARCH:
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index.next = 1
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if syncFlag:
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state.next = t_State.CONFIRM
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elif state == t_State.CONFIRM:
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if index == 0:
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if syncFlag:
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state.next = t_State.SYNC
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else:
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state.next = t_State.SEARCH
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elif state == t_State.SYNC:
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if index == 0:
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if not syncFlag:
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state.next = t_State.SEARCH
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SOF.next = (index == FRAME_SIZE-1)
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else:
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raise ValueError("Undefined state")
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return FSM
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@block
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def testbench():
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SOF = Signal(bool(0))
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syncFlag = Signal(bool(0))
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clk = Signal(bool(0))
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reset_n = Signal(bool(1))
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state = Signal(t_State.SEARCH)
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framectrl = FramerCtrl(SOF, state, syncFlag, clk, reset_n)
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@always(delay(10))
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def clkgen():
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clk.next = not clk
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@instance
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def stimulus():
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for i in range(3):
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yield clk.posedge
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for n in (12, 8, 8, 4):
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syncFlag.next = 1
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yield clk.posedge
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syncFlag.next = 0
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for i in range(n-1):
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yield clk.posedge
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raise StopSimulation
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return framectrl, clkgen, stimulus
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def main():
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tb = testbench()
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tb.config_sim(trace=True)
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tb.run_sim()
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if __name__ == '__main__':
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main()
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