ethernet/tb/nrzi_encode.py

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# SPDX-License-Identifier: AGPL-3.0-Only
# Copyright (C) 2022 Sean Anderson <seanga2@gmail.com>
import random
import cocotb
from cocotb.clock import Clock
from cocotb.triggers import FallingEdge, RisingEdge, Timer
from .util import compare_lists
def nrzi_encode(bits):
last = 1
for bit in bits:
yield (last := last ^ bit)
@cocotb.test(timeout_time=100, timeout_unit='us')
async def test_encode(encoder):
ins = [random.randrange(2) for _ in range(1000)]
encoder.nrz.value = ins[0]
await Timer(1)
await cocotb.start(Clock(encoder.clk, 8, units='ns').start())
async def send_nrz():
for bit in ins:
await FallingEdge(encoder.clk)
encoder.nrz.value = bit
await cocotb.start(send_nrz())
outs = []
await RisingEdge(encoder.clk)
await RisingEdge(encoder.clk)
for _ in ins:
await RisingEdge(encoder.clk)
outs.append(encoder.nrzi.value)
# Ignore the first bit, since it is influenced by the initial value
compare_lists(list(nrzi_encode(ins[1:])), outs[1:])