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# SPDX-License-Identifier: CC0-1.0
import os
import random
from pathlib import Path
import cocotb
from cocotb.clock import Clock
from cocotb.runner import get_runner
from cocotb.triggers import RisingEdge
from cocotb.types import LogicArray
@cocotb.test()
async def dff_simple_test(dut):
"""Test that d propagates to q"""
# Assert initial output is unknown
# verilator does not support 4-state signals
# see https://veripool.org/guide/latest/languages.html#unknown-states
initial = (
LogicArray(0)
if cocotb.SIM_NAME.lower().startswith("verilator")
else (
LogicArray("U")
if cocotb.LANGUAGE.lower().startswith("vhdl")
else LogicArray("X")
)
)
assert LogicArray(dut.q.value) == initial
# Set initial input value to prevent it from floating
dut.d.value = 0
clock = Clock(dut.clk, 10, units="us") # Create a 10us period clock on port clk
# Start the clock. Start it low to avoid issues on the first RisingEdge
cocotb.start_soon(clock.start(start_high=False))
# Synchronize with the clock. This will regisiter the initial `d` value
await RisingEdge(dut.clk)
expected_val = 0 # Matches initial input value
for i in range(10):
val = random.randint(0, 1)
dut.d.value = val # Assign the random value val to the input port d
await RisingEdge(dut.clk)
assert dut.q.value == expected_val, f"output q was incorrect on the {i}th cycle"
expected_val = val # Save random value for next RisingEdge
# Check the final input on the next clock
await RisingEdge(dut.clk)
assert dut.q.value == expected_val, "output q was incorrect on the last cycle"
def test_simple_dff_runner():
hdl_toplevel_lang = os.getenv("HDL_TOPLEVEL_LANG", "verilog")
sim = os.getenv("SIM", "icarus")
proj_path = Path(__file__).resolve().parent
verilog_sources = []
vhdl_sources = []
if hdl_toplevel_lang == "verilog":
verilog_sources = [proj_path / "dff.sv"]
else:
vhdl_sources = [proj_path / "dff.vhdl"]
runner = get_runner(sim)
runner.build(
verilog_sources=verilog_sources,
vhdl_sources=vhdl_sources,
hdl_toplevel="dff",
always=True,
)
runner.test(hdl_toplevel="dff", test_module="test_dff,")
if __name__ == "__main__":
test_simple_dff_runner()
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