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Add test for PCIe spread spectrum clocking

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Signed-off-by: Alex Forencich <alex@alexforencich.com>
This commit is contained in:
Alex Forencich 2023-12-01 22:02:09 -08:00
parent 36cf9c9b06
commit 89ee44d410
1 changed files with 34 additions and 0 deletions
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34
tb/ptp_td_leaf/test_ptp_td_leaf.py
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@ -421,6 +421,40 @@ async def run_test(dut):
assert abs(mean(rel_diffs)) < 5
assert abs(mean(tod_diffs)) < 5
await RisingEdge(dut.clk)
tb.log.info("Coherent tracking (250 MHz +0/-0.5%)")
tb.set_ptp_clock_period(6.4)
tb.set_clock_period(4.0)
await RisingEdge(dut.clk)
period = 4.000
step = 0.0002
period_min = 4.0
period_max = 4.0*(1+0.005)
for i in range(5000):
period += step
if period <= period_min:
step = abs(step)
if period >= period_max:
step = -abs(step)
tb.set_clock_period(period)
for i in range(20):
await RisingEdge(dut.clk)
assert tb.dut.locked.value.integer
rel_diffs, tod_diffs = await tb.measure_ts_diff()
tb.log.info(f"Difference (rel): {mean(rel_diffs)} ns (stdev: {stdev(rel_diffs)})")
tb.log.info(f"Difference (ToD): {mean(tod_diffs)} ns (stdev: {stdev(tod_diffs)})")
assert abs(mean(rel_diffs)) < 5
assert abs(mean(tod_diffs)) < 5
await RisingEdge(dut.clk)
tb.log.info("Significantly slower (100 MHz)")