Triggers are used to indicate when the cocotb scheduler should resume coroutine execution.
To use a trigger, a coroutine should
This will cause execution of the current coroutine to pause.
When the trigger fires, execution of the paused coroutine will resume:
async def coro(): print("Some time before the edge") await RisingEdge(clk) print("Immediately after the edge")
Fires on the rising edge of signal, on a transition from
Fires on the falling edge of signal, on a transition from
ClockCycles(signal, num_cycles, rising=True)[source]¶
Fires after num_cycles transitions of signal from
Timer(time=None, units='step', *, time_ps=None)[source]¶
Fires after the specified simulation time period has elapsed.
time (numbers.Real or decimal.Decimal) –
The time value.
Changed in version 1.5.0: Previously this argument was misleadingly called time_ps.
units (str, optional) – One of
'sec'. When units is
'step', the timestep is determined by the simulator (see
>>> await Timer(100, units='ps')
The time can also be a
>>> await Timer(100e-9, units='sec')
which is particularly convenient when working with frequencies:
>>> freq = 10e6 # 10 MHz >>> await Timer(1 / freq, units='sec')
Other builtin exact numeric types can be used too:
>>> from fractions import Fraction >>> await Timer(Fraction(1, 10), units='ns')
>>> from decimal import Decimal >>> await Timer(Decimal('100e-9'), units='sec')
These are most useful when using computed durations while avoiding floating point inaccuracies.
TriggerException – If a negative value is passed for Timer setup.
Changed in version 1.5: Raise an exception when Timer uses a negative value as it is undefined behavior. Warn for 0 as this will cause erratic behavior in some simulators as well.
Changed in version 1.5: Support
'step'as the the units argument to mean “simulator time step”.
Deprecated since version 1.5: Using None as the the units argument is deprecated, use
Fires when the current simulation timestep moves to the read-only phase.
The read-only phase is entered when the current timestep no longer has any further delta steps. This will be a point where all the signal values are stable as there are no more RTL events scheduled for the timestep. The simulator will not allow scheduling of more events in this timestep. Useful for monitors which need to wait for all processes to execute (both RTL and cocotb) to ensure sampled signal values are final.
Fires when the read-write portion of the simulation cycles is reached.
Fires when all of triggers have fired.
Like most triggers, this simply returns itself.
This is similar to Verilog’s
Fires when the first trigger in triggers fires.
Returns the result of the trigger that fired.
This is similar to Verilog’s
The event loop is single threaded, so while events may be simultaneous in simulation time, they can never be simultaneous in real time. For this reason, the value of
t_ret is t1in the following example is implementation-defined, and will vary by simulator:
t1 = Timer(10, units='ps') t2 = Timer(10, units='ps') t_ret = await First(t1, t2)
In the old-style generator-based coroutines,
t = yield [a, b]was another spelling of
t = yield First(a, b). This spelling is no longer available when using
Fires when a
fork()ed coroutine completes.
The result of blocking on the trigger can be used to get the coroutine result:
async def coro_inner(): await Timer(1, units='ns') return "Hello world" task = cocotb.fork(coro_inner()) result = await Join(task) assert result == "Hello world"
If the coroutine threw an exception, the
awaitwill re-raise it.
The return value of the joined coroutine.
Typically there is no need to use this attribute - the following code samples are equivalent:
forked = cocotb.fork(mycoro()) j = Join(forked) await j result = j.retval
forked = cocotb.fork(mycoro()) result = await Join(forked)
These are not
Triggers themselves, but contain methods that can be used as triggers.
These are used to synchronize coroutines with each other.
Event to permit synchronization between two coroutines.
wait()from one coroutine will block the coroutine until
set()is called somewhere else.
Get a trigger which fires when another coroutine sets the event.
If the event has already been set, the trigger will fire immediately.
To reset the event (and enable the use of
clear()should be called.
Clear this event that has fired.
Subsequent calls to
wait()will block until
set()is called again.
Lock primitive (not re-entrant).
This can be used as:
await lock.acquire() try: # do some stuff finally: lock.release()
Changed in version 1.4: The lock can be used as an asynchronous context manager in an
async with lock: # do some stuff
Trueif the lock is held.
with_timeout(trigger, timeout_time, timeout_unit='step')[source]¶
Waits on triggers, throws an exception if it waits longer than the given time.
await with_timeout(coro, 100, 'ns') await with_timeout(First(coro, event.wait()), 100, 'ns')
RunningTask) – A single object that could be right of an
awaitexpression in cocotb.
timeout_time (numbers.Real or decimal.Decimal) – Simulation time duration before timeout occurs.
timeout_unit (str, optional) – Units of timeout_time, accepts any units that
First trigger that completed if timeout did not occur.
SimTimeoutError – If timeout occurs.
New in version 1.3.
Deprecated since version 1.5: Using None as the the timeout_unit argument is deprecated, use