Library Reference

Test Results

The exceptions in this module can be raised at any point by any code and will terminate the test.

cocotb.result.raise_error(obj, msg)

Creates a TestError exception and raises it after printing a traceback.

Parameters:

• obj – Object with a log method.
• msg (str) – The log message.

cocotb.result.create_error(obj, msg)

Like raise_error(), but return the exception rather than raise it, simply to avoid too many levels of nested try/except blocks.

Parameters:

• obj – Object with a log method.
• msg (str) – The log message.

exception cocotb.result.ReturnValue(retval)

Helper exception needed for Python versions prior to 3.3.

exception cocotb.result.TestComplete(*args, **kwargs)

Exception showing that test was completed. Sub-exceptions detail the exit status.

exception cocotb.result.ExternalException(exception)

Exception thrown by external functions.

exception cocotb.result.TestError(*args, **kwargs)

Exception showing that test was completed with severity Error.

exception cocotb.result.TestFailure(*args, **kwargs)

Exception showing that test was completed with severity Failure.

exception cocotb.result.TestSuccess(*args, **kwargs)

Exception showing that test was completed successfully.

exception cocotb.result.SimFailure(*args, **kwargs)

Exception showing that simulator exited unsuccessfully.

Writing and Generating tests

class cocotb.test(timeout=None, expect_fail=False, expect_error=False, skip=False, stage=None)

Decorator to mark a function as a test

All tests are coroutines. The test decorator provides some common reporting etc, a test timeout and allows us to mark tests as expected failures.

Parameters:

• timeout (int, optional) – value representing simulation timeout (not implemented).
• expect_fail (bool, optional) – Don’t mark the result as a failure if the test fails.
• expect_error (bool, optional) – Don’t mark the result as an error if an error is raised. This is for cocotb internal regression use.
• skip (bool, optional) – Don’t execute this test as part of the regression.
• stage (int, optional) – Order tests logically into stages, where multiple tests can share a stage.

class cocotb.coroutine(func)

Decorator class that allows us to provide common coroutine mechanisms:

log methods will will log to cocotb.coroutines.name

join() method returns an event which will fire when the coroutine exits

class cocotb.regression.TestFactory(test_function, *args, **kwargs)

Used to automatically generate tests.

Assuming we have a common test function that will run a test. This test function will take keyword arguments (for example generators for each of the input interfaces) and generate tests that call the supplied function.

This Factory allows us to generate sets of tests based on the different permutations of the possible arguments to the test function.

For example if we have a module that takes backpressure and idles and have some packet generation routines gen_a and gen_b:

>>> tf = TestFactory(run_test)
>>> tf.add_option('data_in', [gen_a, gen_b])
>>> tf.add_option('backpressure', [None, random_backpressure])
>>> tf.add_option('idles', [None, random_idles])
>>> tf.generate_tests()

We would get the following tests:

• gen_a with no backpressure and no idles
• gen_a with no backpressure and random_idles
• gen_a with random_backpressure and no idles
• gen_a with random_backpressure and random_idles
• gen_b with no backpressure and no idles
• gen_b with no backpressure and random_idles
• gen_b with random_backpressure and no idles
• gen_b with random_backpressure and random_idles

The tests are appended to the calling module for auto-discovery.

Tests are simply named test_function_N. The docstring for the test (hence the test description) includes the name and description of each generator.

add_option(name, optionlist)

Add a named option to the test.

Parameters:

• name (str) – Name of the option. Passed to test as a keyword argument.
• optionlist (list) – A list of possible options for this test knob.

generate_tests(prefix='', postfix='')

Generates exhaustive set of tests using the cartesian product of the possible keyword arguments.

The generated tests are appended to the namespace of the calling module.

Parameters:

• prefix (str) – Text string to append to start of test_function name when naming generated test cases. This allows reuse of a single test_function with multiple TestFactories without name clashes.
• postfix (str) – Text string to append to end of test_function name when naming generated test cases. This allows reuse of a single test_function with multiple TestFactories without name clashes.

class cocotb.hook

Decorator to mark a function as a hook for cocotb

All hooks are run at the beginning of a cocotb test suite, prior to any test code being run.

Interacting with the Simulator

class cocotb.binary.BinaryRepresentation

UNSIGNED = 0

Unsigned format

SIGNED_MAGNITUDE = 1

Sign and magnitude format

TWOS_COMPLEMENT = 2

Two’s complement format

class cocotb.binary.BinaryValue(value=None, n_bits=None, bigEndian=True, binaryRepresentation=0, bits=None)

Representation of values in binary format.

The underlying value can be set or accessed using these aliasing attributes:

• BinaryValue.integer is an integer
• BinaryValue.signed_integer is a signed integer
• BinaryValue.binstr is a string of “01xXzZ”
• BinaryValue.buff is a binary buffer of bytes
• BinaryValue.value is an integer deprecated

For example:

>>> vec = BinaryValue()
>>> vec.integer = 42
>>> print(vec.binstr)
101010
>>> print(repr(vec.buff))
'*'

assign(value)

Decides how best to assign the value to the vector.

We possibly try to be a bit too clever here by first of all trying to assign the raw string as a binstring, however if the string contains any characters that aren’t 0, 1, X or Z then we interpret the string as a binary buffer.

Parameters:value (str or int or long) – The value to assign.

get_value()

Return the integer representation of the underlying vector.

get_value_signed()

Return the signed integer representation of the underlying vector.

is_resolvable

Does the value contain any X’s? Inquiring minds want to know.

value

Integer access to the value. deprecated

integer

The integer representation of the underlying vector.

signed_integer

The signed integer representation of the underlying vector.

get_buff()

Attribute buff represents the value as a binary string buffer.

>>> "0100000100101111".buff == "A/"
True

buff

Access to the value as a buffer.

get_binstr()

Attribute binstr is the binary representation stored as a string of 1 and 0.

binstr

Access to the binary string.

n_bits

Access to the number of bits of the binary value.

class cocotb.bus.Bus(entity, name, signals, optional_signals=[], bus_separator='_', array_idx=None)

Wraps up a collection of signals.

Assumes we have a set of signals/nets named entity.<bus_name>_<signal>.

For example a bus stream_in with signals valid and data is assumed to be named dut.stream_in_valid and dut.stream_in_data.

Todo

Support for struct/record ports where signals are member names.

drive(obj, strict=False)

Drives values onto the bus.

Parameters:

• obj – Object with attribute names that match the bus signals.
• strict (bool, optional) – Check that all signals are being assigned.

Raises:

AttributeError – If not all signals have been assigned when strict=True.

capture()

Capture the values from the bus, returning an object representing the capture.

Returns:A dictionary that supports access by attribute, where each attribute corresponds to each signal’s value. Return type:dict Raises:RuntimeError – If signal not present in bus, or attempt to modify a bus capture.

sample(obj, strict=False)

Sample the values from the bus, assigning them to obj.

Parameters:

• obj – Object with attribute names that match the bus signals.
• strict (bool, optional) – Check that all signals being sampled are present in obj.

Raises:

AttributeError – If attribute is missing in obj when strict=True.

class cocotb.clock.Clock(signal, period, units=None)

Simple 50:50 duty cycle clock driver.

Instances of this class should call its start method and fork the result. This will create a clocking thread that drives the signal at the desired period/frequency.

Example:

c = Clock(dut.clk, 10, 'ns')
cocotb.fork(c.start())

Parameters:

• signal – The clock pin/signal to be driven.
• period (int) – The clock period. Must convert to an even number of timesteps.
• units (str, optional) – One of None, 'fs', 'ps', 'ns', 'us', 'ms', 'sec'. When no units is given (None) the timestep is determined by the simulator.

Triggers

Triggers are used to indicate when the scheduler should resume coroutine execution. Typically a coroutine will yield a trigger or a list of triggers.

Simulation Timing

class cocotb.triggers.Timer(time_ps, units=None)

Execution will resume when the specified time period expires.

Consumes simulation time.

class cocotb.triggers.ReadOnly

Execution will resume when the readonly portion of the sim cycles is reached.

class cocotb.triggers.NextTimeStep

Execution will resume when the next time step is started.

class cocotb.triggers.ClockCycles(signal, num_cycles, rising=True)

Execution will resume after num_cycles rising edges or num_cycles falling edges.

Signal related

class cocotb.triggers.Edge(signal)

Triggers on either edge of the provided signal.

class cocotb.triggers.RisingEdge(signal)

Triggers on the rising edge of the provided signal.

class cocotb.triggers.FallingEdge(signal)

Triggers on the falling edge of the provided signal.

Python Triggers

class cocotb.triggers.Event(name='')

Event to permit synchronisation between two coroutines.

set(data=None)

Wake up any coroutines blocked on this event.

wait()

This can be yielded to block this coroutine until another wakes it.

If the event has already been fired, this returns NullTrigger. To reset the event (and enable the use of wait again), clear() should be called.

clear()

Clear this event that has fired.

Subsequent calls to wait() will block until set() is called again.

class cocotb.triggers.Lock(name='')

Lock primitive (not re-entrant).

acquire()

This can be yielded to block until the lock is acquired.

class cocotb.triggers.Join(coroutine)

Join a coroutine, firing when it exits.

Testbench Structure

Driver

class cocotb.drivers.Driver

Class defining the standard interface for a driver within a testbench.

The driver is responsible for serialising transactions onto the physical pins of the interface. This may consume simulation time.

append(transaction, callback=None, event=None, **kwargs)

Queue up a transaction to be sent over the bus.

Mechanisms are provided to permit the caller to know when the transaction is processed.

Parameters:

• transaction (any) – The transaction to be sent.
• callback (callable, optional) – Optional function to be called when the transaction has been sent.
• event (optional) – Event to be set when the transaction has been sent.
• **kwargs – Any additional arguments used in child class’ _driver_send method.

clear()

Clear any queued transactions without sending them onto the bus.

send

Blocking send call (hence must be “yielded” rather than called).

Sends the transaction over the bus.

Parameters:

• transaction (any) – The transaction to be sent.
• sync (bool, optional) – Synchronise the transfer by waiting for rising edge.
• **kwargs (dict) – Additional arguments used in child class’ _driver_send method.

_driver_send(transaction, sync=True, **kwargs)

Actual implementation of the send.

Subclasses should override this method to implement the actual send() routine.

Parameters:

• transaction (any) – The transaction to be sent.
• sync (boolean, optional) – Synchronise the transfer by waiting for rising edge.
• **kwargs – Additional arguments if required for protocol implemented in subclass.

_send

Send coroutine.

Parameters:

• transaction (any) – The transaction to be sent.
• callback (callable, optional) – Optional function to be called when the transaction has been sent.
• event (optional) – event to be set when the transaction has been sent.
• sync (boolean, optional) – Synchronise the transfer by waiting for rising edge.
• **kwargs – Any additional arguments used in child class’ _driver_send method.

class cocotb.drivers.BitDriver(signal, clk, generator=None)

Bases: object

Drives a signal onto a single bit.

Useful for exercising ready / valid.

class cocotb.drivers.BusDriver(entity, name, clock, **kwargs)

Bases: cocotb.drivers.Driver

Wrapper around common functionality for busses which have:

• a list of _signals (class attribute)
• a list of _optional_signals (class attribute)
• a clock
• a name
• an entity

Parameters:

• entity (SimHandle) – A handle to the simulator entity.
• name (str or None) – Name of this bus. None for nameless bus, e.g. bus-signals in an interface or a modport. (untested on struct/record, but could work here as well).
• clock (SimHandle) – A handle to the clock associated with this bus.
• array_idx (int or None, optional) – Optional index when signal is an array.

_wait_for_signal

This method will return with the specified signal has hit logic 1. The state will be in the ReadOnly phase so sim will need to move to NextTimeStep before registering more callbacks can occur.

_wait_for_nsignal

This method will return with the specified signal has hit logic 0. The state will be in the ReadOnly phase so sim will need to move to NextTimeStep before registering more callbacks can occur.

Monitor

class cocotb.monitors.Monitor(callback=None, event=None)

Base class for Monitor objects.

Monitors are passive ‘listening’ objects that monitor pins in or out of a DUT. This class should not be used directly, but should be subclassed and the internal _monitor_recv method should be overridden and decorated as a coroutine. This _monitor_recv method should capture some behavior of the pins, form a transaction, and pass this transaction to the internal _recv method. The _monitor_recv method is added to the cocotb scheduler during the __init__ phase, so it should not be yielded anywhere.

The primary use of a Monitor is as an interface for a Scoreboard.

Parameters:

• callback (callable) – Callback to be called with each recovered transaction as the argument. If the callback isn’t used, received transactions will be placed on a queue and the event used to notify any consumers.
• event (event) – Object that supports a set method that will be called when a transaction is received through the internal _recv method.

_monitor_recv

Actual implementation of the receiver.

Subclasses should override this method to implement the actual receive routine and call _recv with the recovered transaction.

_recv(transaction)

Common handling of a received transaction.

class cocotb.monitors.BusMonitor(entity, name, clock, reset=None, reset_n=None, callback=None, event=None, bus_separator='_', array_idx=None)

Bases: cocotb.monitors.Monitor

Wrapper providing common functionality for monitoring busses.

Scoreboard

Common scoreboarding capability.

class cocotb.scoreboard.Scoreboard(dut, reorder_depth=0, fail_immediately=True)

Bases: object

Generic scoreboarding class.

We can add interfaces by providing a monitor and an expected output queue.

The expected output can either be a function which provides a transaction or a simple list containing the expected output.

Todo

Statistics for end-of-test summary etc.

Parameters:

• dut (SimHandle) – Handle to the DUT.
• reorder_depth (int, optional) – Consider up to reorder_depth elements of the expected result list as passing matches. Default is 0, meaning only the first element in the expected result list is considered for a passing match.
• fail_immediately (bool, optional) – Raise TestFailure immediately when something is wrong instead of just recording an error. Default is True.

result

Determine the test result, do we have any pending data remaining?

Returns:If not all expected output was received or error were recorded during the test. Return type:TestFailure

compare(got, exp, log, strict_type=True)

Common function for comparing two transactions.

Can be re-implemented by a subclass.

Parameters:

• got – The received transaction.
• exp – The expected transaction.
• log – The logger for reporting messages.
• strict_type (bool, optional) – Require transaction type to match exactly if True, otherwise compare its string representation.

Raises:

TestFailure – If received transaction differed from expected transaction when fail_immediately is True. If strict_type is True, also the transaction type must match.

add_interface(monitor, expected_output, compare_fn=None, reorder_depth=0, strict_type=True)

Add an interface to be scoreboarded.

Provides a function which the monitor will callback with received transactions.

Simply check against the expected output.

Parameters:

• monitor – The monitor object.
• expected_output – Queue of expected outputs.
• compare_fn (callable, optional) –
• reorder_depth (int, optional) – Consider up to reorder_depth elements of the expected result list as passing matches. Default is 0, meaning only the first element in the expected result list is considered for a passing match.
• strict_type (bool, optional) – Require transaction type to match exactly if True, otherwise compare its string representation.

Raises:

TypeError – If no monitor is on the interface or compare_fn is not a callable function.

Clock

class cocotb.clock.Clock(signal, period, units=None)

Simple 50:50 duty cycle clock driver.

Instances of this class should call its start method and fork the result. This will create a clocking thread that drives the signal at the desired period/frequency.

Example:

c = Clock(dut.clk, 10, 'ns')
cocotb.fork(c.start())

Parameters:

• signal – The clock pin/signal to be driven.
• period (int) – The clock period. Must convert to an even number of timesteps.
• units (str, optional) – One of None, 'fs', 'ps', 'ns', 'us', 'ms', 'sec'. When no units is given (None) the timestep is determined by the simulator.

start

Clocking coroutine. Start driving your clock by forking a call to this.

Parameters:cycles (int, optional) – Cycle the clock cycles number of times, or if None then cycle the clock forever. Note: 0 is not the same as None, as 0 will cycle no times.

Utilities

cocotb.utils.get_sim_time(units=None)

Retrieves the simulation time from the simulator.

Parameters:units (str or None, optional) – String specifying the units of the result (one of None, 'fs', 'ps', 'ns', 'us', 'ms', 'sec'). None will return the raw simulation time. Returns:The simulation time in the specified units.

cocotb.utils.get_time_from_sim_steps(steps, units)

Calculates simulation time in the specified units from the steps based on the simulator precision.

Parameters:

• steps (int) – Number of simulation steps.
• units (str) – String specifying the units of the result (one of 'fs', 'ps', 'ns', 'us', 'ms', 'sec').

Returns:

The simulation time in the specified units.

cocotb.utils.get_sim_steps(time, units=None)

Calculates the number of simulation time steps for a given amount of time.

Parameters:

• time (int or float) – The value to convert to simulation time steps.
• units (str or None, optional) – String specifying the units of the result (one of None, 'fs', 'ps', 'ns', 'us', 'ms', 'sec'). None means time is already in simulation time steps.

Returns:

The number of simulation time steps.

Return type:

int

Raises:

ValueError – If given time cannot be represented by simulator precision.

cocotb.utils.pack(ctypes_obj)

Convert a ctypes structure into a Python string.

Parameters:ctypes_obj (ctypes.Structure) – The ctypes structure to convert to a string. Returns:New Python string containing the bytes from memory holding ctypes_obj.

cocotb.utils.unpack(ctypes_obj, string, bytes=None)

Unpack a Python string into a ctypes structure.

If the length of string is not the correct size for the memory footprint of the ctypes structure then the bytes keyword argument must be used.

Parameters:

• ctypes_obj (ctypes.Structure) – The ctypes structure to pack into.
• string (str) – String to copy over the ctypes_obj memory space.
• bytes (int, optional) – Number of bytes to copy. Defaults to None, meaning the length of string is used.

Raises:

• ValueError – If length of string and size of ctypes_obj are not equal.
• MemoryError – If bytes is longer than size of ctypes_obj.

cocotb.utils.hexdump(x)

Hexdump a buffer.

Parameters:x – Object that supports conversion via the str built-in. Returns:A string containing the hexdump.

Example:

print(hexdump('this somewhat long string'))

0000   74 68 69 73 20 73 6F 6D 65 77 68 61 74 20 6C 6F   this somewhat lo
0010   6E 67 20 73 74 72 69 6E 67                        ng string

cocotb.utils.hexdiffs(x, y)

Return a diff string showing differences between two binary strings.

Parameters:

• x – Object that supports conversion via the str built-in.
• y – Object that supports conversion via the str built-in.

Example:

print(hexdiffs('this short thing', 'this also short'))

0000      746869732073686F 7274207468696E67 this short thing
     0000 7468697320616C73 6F  2073686F7274 this also  short

cocotb.utils.with_metaclass(meta, *bases)

This provides:

class Foo(with_metaclass(Meta, Base1, Base2)): pass

which is a unifying syntax for:

# python 3
class Foo(Base1, Base2, metaclass=Meta): pass

# python 2
class Foo(Base1, Base2):
    __metaclass__ = Meta

class cocotb.utils.ParametrizedSingleton(*args, **kwargs)

A metaclass that allows class construction to reuse an existing instance.

We use this so that RisingEdge(sig) and Join(coroutine) always return the same instance, rather than creating new copies.

Simulation Object Handles

class cocotb.handle.SimHandleBase(handle, path)

Bases: object

Base class for all simulation objects.

We maintain a handle which we can use for GPI calls.

class cocotb.handle.RegionObject(handle, path)

Bases: cocotb.handle.SimHandleBase

Region objects don’t have values, they are effectively scopes or namespaces.

class cocotb.handle.HierarchyObject(handle, path)

Bases: cocotb.handle.RegionObject

Hierarchy objects are namespace/scope objects.

class cocotb.handle.HierarchyArrayObject(handle, path)

Bases: cocotb.handle.RegionObject

Hierarchy Arrays are containers of Hierarchy Objects.

class cocotb.handle.NonHierarchyObject(handle, path)

Bases: cocotb.handle.SimHandleBase

Common base class for all non-hierarchy objects.

value

A reference to the value

class cocotb.handle.ConstantObject(handle, path, handle_type)

Bases: cocotb.handle.NonHierarchyObject

Constant objects have a value that can be read, but not set.

We can also cache the value since it is elaboration time fixed and won’t change within a simulation.

class cocotb.handle.NonHierarchyIndexableObject(handle, path)

Bases: cocotb.handle.NonHierarchyObject

class cocotb.handle.NonConstantObject(handle, path)

Bases: cocotb.handle.NonHierarchyIndexableObject

drivers()

An iterator for gathering all drivers for a signal.

loads()

An iterator for gathering all loads on a signal.

class cocotb.handle.ModifiableObject(handle, path)

Bases: cocotb.handle.NonConstantObject

Base class for simulator objects whose values can be modified.

setimmediatevalue(value)

Set the value of the underlying simulation object to value.

This operation will fail unless the handle refers to a modifiable object, e.g. net, signal or variable.

We determine the library call to make based on the type of the value because assigning integers less than 32 bits is faster.

Parameters:value (ctypes.Structure, cocotb.binary.BinaryValue, int, double) – The value to drive onto the simulator object. Raises:TypeError – If target is not wide enough or has an unsupported type for value assignment.

class cocotb.handle.RealObject(handle, path)

Bases: cocotb.handle.ModifiableObject

Specific object handle for Real signals and variables.

setimmediatevalue(value)

Set the value of the underlying simulation object to value.

This operation will fail unless the handle refers to a modifiable object, e.g. net, signal or variable.

Parameters:value (float) – The value to drive onto the simulator object. Raises:TypeError – If target has an unsupported type for real value assignment.

class cocotb.handle.EnumObject(handle, path)

Bases: cocotb.handle.ModifiableObject

Specific object handle for enumeration signals and variables.

setimmediatevalue(value)

Set the value of the underlying simulation object to value.

This operation will fail unless the handle refers to a modifiable object, e.g. net, signal or variable.

Parameters:value (int) – The value to drive onto the simulator object. Raises:TypeError – If target has an unsupported type for integer value assignment.

class cocotb.handle.IntegerObject(handle, path)

Bases: cocotb.handle.ModifiableObject

Specific object handle for Integer and Enum signals and variables.

setimmediatevalue(value)

Set the value of the underlying simulation object to value.

This operation will fail unless the handle refers to a modifiable object, e.g. net, signal or variable.

Parameters:value (int) – The value to drive onto the simulator object. Raises:TypeError – If target has an unsupported type for integer value assignment.

class cocotb.handle.StringObject(handle, path)

Bases: cocotb.handle.ModifiableObject

Specific object handle for String variables.

setimmediatevalue(value)

Set the value of the underlying simulation object to value.

This operation will fail unless the handle refers to a modifiable object, e.g. net, signal or variable.

Parameters:value (str) – The value to drive onto the simulator object. Raises:TypeError – If target has an unsupported type for string value assignment.

cocotb.handle.SimHandle(handle, path=None)

Factory function to create the correct type of SimHandle object.

Implemented Testbench Structures

Drivers

AD9361

Analog Devices AD9361 RF Transceiver.

class cocotb.drivers.ad9361.AD9361(dut, rx_channels=1, tx_channels=1, tx_clock_half_period=16276, rx_clock_half_period=16276, loopback_queue_maxlen=16)

Driver for the AD9361 RF Transceiver.

send_data(i_data, q_data, i_data2=None, q_data2=None, binaryRepresentation=BinaryRepresentation.TWOS_COMPLEMENT)

Forks the rx_data_to_ad9361 coroutine to send data.

Parameters:

• i_data (int) – Data of the I0 channel.
• q_data (int) – Data of the Q0 channel.
• i_data2 (int, optional) – Data of the I1 channel.
• q_data2 (int, optional) – Data of the Q1 channel.
• binaryRepresentation (BinaryRepresentation) – The representation of the binary value. Default is TWOS_COMPLEMENT.

rx_data_to_ad9361(i_data, q_data, i_data2=None, q_data2=None, binaryRepresentation=BinaryRepresentation.TWOS_COMPLEMENT)

Receive data to AD9361.

This is a coroutine.

Parameters:

• i_data (int) – Data of the I0 channel.
• q_data (int) – Data of the Q0 channel.
• i_data2 (int, optional) – Data of the I1 channel.
• q_data2 (int, optional) – Data of the Q1 channel.
• binaryRepresentation (BinaryRepresentation) – The representation of the binary value. Default is TWOS_COMPLEMENT.

ad9361_tx_to_rx_loopback()

Create loopback from tx to rx.

Forks a coroutine doing the actual task.

tx_data_from_ad9361()

Transmit data from AD9361.

Forks a coroutine doing the actual task.

AMBA

Advanced Microcontroller Bus Architecture.

class cocotb.drivers.amba.AXI4LiteMaster(entity, name, clock)

AXI4-Lite Master

TODO: Kill all pending transactions if reset is asserted…

write(address, value, byte_enable=0xf, address_latency=0, data_latency=0)

Write a value to an address.

Parameters:

• address (int) – The address to write to
• value (int) – The data value to write
• byte_enable (int, optional) – Which bytes in value to actually write. Default is to write all bytes.
• address_latency (int, optional) – Delay before setting the address (in clock cycles). Default is no delay.
• data_latency (int, optional) – Delay before setting the data value (in clock cycles). Default is no delay.
• sync (bool, optional) – Wait for rising edge on clock initially. Defaults to True.

Returns:

The write response value

Return type:

BinaryValue

Raises:

AXIProtocolError – If write response from AXI is not OKAY

read(address, sync=True)

Read from an address.

Parameters:

• address (int) – The address to read from
• sync (bool, optional) – Wait for rising edge on clock initially. Defaults to True.

Returns:

The read data value

Return type:

BinaryValue

Raises:

AXIProtocolError – If read response from AXI is not OKAY

Members: Member-order:bysource

class cocotb.drivers.amba.AXI4Slave(entity, name, clock, memory, callback=None, event=None, big_endian=False)

AXI4 Slave

Monitors an internal memory and handles read and write requests.

Avalon

class cocotb.drivers.avalon.AvalonMM(entity, name, clock, **kwargs)

Avalon Memory Mapped Interface (Avalon-MM) Driver.

Currently we only support the mode required to communicate with SF avalon_mapper which is a limited subset of all the signals.

Blocking operation is all that is supported at the moment, and for the near future as well. Posted responses from a slave are not supported.

class cocotb.drivers.avalon.AvalonMaster(entity, name, clock, **kwargs)

Avalon Memory Mapped Interface (Avalon-MM) Master

write(address, value)

Issue a write to the given address with the specified value. See http://www.altera.com/literature/manual/mnl_avalon_spec_1_3.pdf

Parameters:

• address (int) – The address to write to.
• value (int) – The data value to write.

Raises:

TestError – If master is read-only.

read(address, sync=True)

Issue a request to the bus and block until this comes back. Simulation time still progresses but syntactically it blocks. See http://www.altera.com/literature/manual/mnl_avalon_spec_1_3.pdf

Parameters:

• address (int) – The address to read from.
• sync (bool, optional) – Wait for rising edge on clock initially. Defaults to True.

Returns:

The read data value.

Return type:

BinaryValue

Raises:

TestError – If master is write-only.

Members: Member-order:bysource

class cocotb.drivers.avalon.AvalonMemory(entity, name, clock, readlatency_min=1, readlatency_max=1, memory=None, avl_properties={})

Emulate a memory, with back-door access.

class cocotb.drivers.avalon.AvalonST(*args, **kwargs)

Avalon Streaming Interface (Avalon-ST) Driver

class cocotb.drivers.avalon.AvalonSTPkts(*args, **kwargs)

Avalon Streaming Interface (Avalon-ST) Driver, packetised.

OPB

class cocotb.drivers.opb.OPBMaster(entity, name, clock)

On-chip peripheral bus master.

write(address, value, sync=True)

Issue a write to the given address with the specified value.

Parameters:

• address (int) – The address to read from.
• value (int) – The data value to write.
• sync (bool, optional) – Wait for rising edge on clock initially. Defaults to True.

Raises:

OPBException – If write took longer than 16 cycles

read(address, sync=True)

Issue a request to the bus and block until this comes back. Simulation time still progresses but syntactically it blocks.

Parameters:

• address (int) – The address to read from.
• sync (bool, optional) – Wait for rising edge on clock initially. Defaults to True.

Returns:

The read data value.

Return type:

BinaryValue

Raises:

OPBException – If read took longer than 16 cycles.

Members: Member-order:bysource

XGMII

class cocotb.drivers.xgmii.XGMII(signal, clock, interleaved=True)

XGMII (10 Gigabit Media Independent Interface) driver.

static layer1(packet)

Take an Ethernet packet (as a string) and format as a layer 1 packet.

Pad to 64 bytes, prepend preamble and append 4-byte CRC on the end.

Parameters:packet (str) – The Ethernet packet to format. Returns:The formatted layer 1 packet. Return type:str

idle()

Helper function to set bus to IDLE state.

terminate(index)

Helper function to terminate from a provided lane index.

Parameters:index (int) – The index to terminate.

Monitors

Avalon

class cocotb.monitors.avalon.AvalonST(*args, **kwargs)

Avalon-ST bus.

Non-packetised so each valid word is a separate transaction.

class cocotb.monitors.avalon.AvalonSTPkts(*args, **kwargs)

Packetised Avalon-ST bus.

XGMII

class cocotb.monitors.xgmii.XGMII(signal, clock, interleaved=True, callback=None, event=None)

XGMII (10 Gigabit Media Independent Interface) Monitor.

Assumes a single vector, either 4 or 8 bytes plus control bit for each byte.

If interleaved is true then the control bits are adjacent to the bytes.