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Your first signal and event

In this exercise, you will create a 128-bit signal, advance a clock, and register an event that fires after three cycles. Complete installation first and use a Python environment with xspcomm installed.

1. Store a wide signal

Save this code as first_event.py:

import xspcomm as xs

signal = xs.XData(128, xs.XData.InOut)
signal.value = (1 << 100) | 0x5A
print(hex(signal.value))
assert signal.value == (1 << 100) | 0x5A

Run python3 first_event.py. The output should be:

0x1000000000000000000000005a

XData(128, ...) sets the width, and InOut allows reading and writing. .value uses Python integers, so it can hold both bit 100 and the low bits 0x5A.

2. Advance a clock

Replace the script with:

import xspcomm as xs

clock = xs.XClock(lambda dump: 0)
clock.Step(2)
print(f"cycles={clock.clk}, half_ticks={clock.GetHalfTick()}")

Run it again:

cycles=2, half_ticks=4

XClock accepts an execution function. The empty function in this exercise lets us observe time counters on their own; with a circuit, this function calls the simulator. Step(2) runs two complete cycles, each containing two half cycles.

3. Wait for three cycles

Now use the execution engine to wait for an event. Replace the script with this complete version:

import xspcomm as xs

clock = xs.XClock(lambda dump: 0)
clock.Step(2)
engine = xs.XTriggerEngine(clock)
engine.AcquireClock()
try:
    handle = engine.ArmClockCycles(3)
    result = engine.RunUntil(20)
    assert result.advanced_ticks == 6
    assert len(result.hits) == 1
    assert result.hits[0].slot == handle.slot
    print(f"advanced={result.advanced_ticks}, hits={len(result.hits)}")
    engine.Disarm(handle)
finally:
    engine.Clear()
    engine.ReleaseClock()
clock.Step(1)
print(f"cycles={clock.clk}")
assert clock.clk == 6

The output is:

advanced=6, hits=1
cycles=6

AcquireClock() gives the engine control of clock advancement. ArmClockCycles(3) registers an event after three cycles. RunUntil(20) allows up to twenty half cycles. The event fires after six half cycles and the engine returns, so advanced_ticks is 6.

Disarm() removes the processed registration. After cleanup and ReleaseClock(), the script advances one more cycle manually, giving a total of 2 + 3 + 1 = 6.

Next, replace the cycle event with signal conditions and coverage sampling. See XEngine and Trigger for signatures and sampling phases.