Links

File: UVM Links

The <UVMLinkBase> class, and its extensions, are provided as a mechanism to allow for compile-time safety when trying to establish links between records within a <uvm_tr_database>.

class uvm.base.uvm_links.UVMLinkBase(name='unnamed-UVMLinkBase')

Bases: UVMObject

CLASS: UVMLinkBase

The ~UVMLinkBase~ class presents a simple API for defining a link between any two objects.

Using extensions of self class, a <uvm_tr_database> can determine the type of links being passed, without relying on “magic” string names.

For example:

def do_establish_link(self, link):
  pc_link: UVMParentChildLink = None
  ce_link: UVMCauseEffectLink = None

  if (sv.cast(pc_link, link)):
     # Record the parent-child relationship
  elif (sv.cast(ce_link, link)):
     # Record the cause-effect relationship
  else:
     # Unsupported relationship!

set_lhs(lhs: UVMObject)

Group: Accessors

Function: set_lhs Sets the left-hand-side of the link

Triggers the do_set_lhs callback.

Parameters

lhs –

get_lhs() → UVMObject

Function: get_lhs Gets the left-hand-side of the link

Triggers the do_get_lhs callback

Returns:

set_rhs(rhs: UVMObject) → None

Function: set_rhs Sets the right-hand-side of the link

Triggers the do_set_rhs callback.

Parameters

rhs –

get_rhs() → UVMObject

Function: get_rhs Gets the right-hand-side of the link

Triggers the do_get_rhs callback

Returns:

set(lhs: UVMObject, rhs: UVMObject) → None

Function: set Convenience method for setting both sides in one call.

Triggers both the do_set_rhs and do_set_lhs callbacks.

Parameters

• lhs –

• rhs –

do_set_lhs(lhs: UVMObject) → None

do_get_lhs()

do_set_rhs(rhs: UVMObject) → None

do_get_rhs()

class uvm.base.uvm_links.UVMParentChildLink(name='unnamed-UVMParentChildLink')

Bases: UVMLinkBase

CLASS: UVMParentChildLink

The ~UVMParentChildLink~ is used to represent a Parent/Child relationship between two objects.

classmethod get_link(lhs: UVMObject, rhs: UVMObject, name='pc_link') → UVMParentChildLink

Function: get_link Constructs a pre-filled link

This allows for simple one-line link creations.

| my_db.establish_link(UVMParentChildLink::get_link(record1, record2))

Parameters:
lhs - Left hand side reference
rhs - Right hand side reference
name - Optional name for the link object

Parameters

• cls –

• lhs –

• rhs –

• name –

Returns:

do_set_lhs(lhs)

Group: Implementation Callbacks

Function: do_set_lhs Sets the left-hand-side (Parent)

Parameters

lhs –

do_get_lhs()

Function: do_get_lhs Retrieves the left-hand-side (Parent)

Returns:

do_set_rhs(rhs)

Function: do_set_rhs Sets the right-hand-side (Child)

Parameters

rhs –

do_get_rhs()

Function: do_get_rhs Retrieves the right-hand-side (Child)

Returns:

create(name='')

Group: Creation

The create method allocates a new object of the same type as this object and returns it via a base uvm_object handle. Every class deriving from uvm_object, directly or indirectly, must implement the create method.

A typical implementation is as follows:

class mytype (UVMObject):
  ...
  def create(self, name=""):
    mytype t = mytype(name)
    return t

Parameters

name (str) – Name of the created object.

Returns

New object.

Return type

obj

get_object_type()

Function: get_object_type

Returns the type-proxy (wrapper) for this object. The uvm_factory’s type-based override and creation methods take arguments of uvm_object_wrapper. This method, if implemented, can be used as convenient means of supplying those arguments. This method is the same as the static get_type method, but uses an already allocated object to determine the type-proxy to access (instead of using the static object).

The default implementation of this method does a factory lookup of the proxy using the return value from get_type_name. If the type returned by get_type_name is not registered with the factory, then a None handle is returned.

For example:

class cmd (UVMObject):
  type_id = UVMObjectRegistry()
  @classmethod
  def type_id get_type(cls):
    return type_id.get()
  def get_object_type(self):
    return cmd.type_id.get()

This function is implemented by the `uvm_*_utils macros, if employed.

Returns:

classmethod get_type()

Returns the type-proxy (wrapper) for this object. The UVMFactory’s type-based override and creation methods take arguments of uvm_object_wrapper. This method, if implemented, can be used as convenient means of supplying those arguments.

The default implementation of this method produces an error and returns None. To enable use of this method, a user’s subtype must implement a version that returns the subtype’s wrapper.

For example:

class cmd(UVMObject):
  type_id = None

  @classmethod
  def get_type(cls):
    return cls.type_id.get()

Then, to use:

factory.set_type_override(cmd.get_type(), subcmd.get_type())

This function is implemented by the uvm_*_utils functions, if employed.

Returns:

get_type_name()

This function returns the type name of the object, which is typically the type identifier enclosed in quotes. It is used for various debugging functions in the library, and it is used by the factory for creating objects.

This function must be defined in every derived class.

A typical implementation is as follows:

class mytype (UVMObject):
  ...
  type_name = "mytype"

  def get_type_name(self):
    return my_type.type_name

We define the type_name static variable to enable access to the type name without need of an object of the class, i.e., to enable access via the scope operator, ~mytype::type_name~.

Returns

Type name of the object.

Return type

str

type_id = <uvm.base.uvm_registry.UVMObjectRegistry object>

type_name = 'UVMParentChildLink'

class uvm.base.uvm_links.UVMCauseEffectLink(name='unnamed-UVMCauseEffectLink')

Bases: UVMLinkBase

CLASS: UVMCauseEffectLink

The ~UVMCauseEffectLink~ is used to represent a Cause/Effect relationship between two objects.

classmethod get_link(lhs, rhs, name='ce_link') → UVMCauseEffectLink

Function: get_link Constructs a pre-filled link

This allows for simple one-line link creations.

| my_db.establish_link(UVMCauseEffectLink::get_link(record1, record2))

Parameters:
lhs - Left hand side reference
rhs - Right hand side reference
name - Optional name for the link object

Parameters

• cls –

• lhs –

• rhs –

• name –

Returns:

do_set_lhs(lhs)

Group: Implementation Callbacks

Function: do_set_lhs Sets the left-hand-side (Cause)

Parameters

lhs –

do_get_lhs()

Function: do_get_lhs Retrieves the left-hand-side (Cause)

Returns:

do_set_rhs(rhs)

Function: do_set_rhs Sets the right-hand-side (Effect)

Parameters

rhs –

do_get_rhs()

Function: do_get_rhs Retrieves the right-hand-side (Effect)

Returns:

class uvm.base.uvm_links.UVMRelatedLink(name='unnamed-UVMRelatedLink')

Bases: UVMLinkBase

CLASS: UVMRelatedLink

The ~UVMRelatedLink~ is used to represent a generic “is related” link between two objects.

classmethod get_link(lhs, rhs, name='ce_link') → UVMRelatedLink

Function: get_link Constructs a pre-filled link

This allows for simple one-line link creations.

| my_db.establish_link(UVMRelatedLink::get_link(record1, record2))

Parameters

• lhs – Left hand side reference

• rhs – Right hand side reference

• name (str) – Optional name for the link object

Returns

Created related link.

Return type

UVMRelatedLink

create(name='')

Group: Creation

The create method allocates a new object of the same type as this object and returns it via a base uvm_object handle. Every class deriving from uvm_object, directly or indirectly, must implement the create method.

A typical implementation is as follows:

class mytype (UVMObject):
  ...
  def create(self, name=""):
    mytype t = mytype(name)
    return t

Parameters

name (str) – Name of the created object.

Returns

New object.

Return type

obj

get_object_type()

Function: get_object_type

Returns the type-proxy (wrapper) for this object. The uvm_factory’s type-based override and creation methods take arguments of uvm_object_wrapper. This method, if implemented, can be used as convenient means of supplying those arguments. This method is the same as the static get_type method, but uses an already allocated object to determine the type-proxy to access (instead of using the static object).

The default implementation of this method does a factory lookup of the proxy using the return value from get_type_name. If the type returned by get_type_name is not registered with the factory, then a None handle is returned.

For example:

class cmd (UVMObject):
  type_id = UVMObjectRegistry()
  @classmethod
  def type_id get_type(cls):
    return type_id.get()
  def get_object_type(self):
    return cmd.type_id.get()

This function is implemented by the `uvm_*_utils macros, if employed.

Returns:

classmethod get_type()

Returns the type-proxy (wrapper) for this object. The UVMFactory’s type-based override and creation methods take arguments of uvm_object_wrapper. This method, if implemented, can be used as convenient means of supplying those arguments.

The default implementation of this method produces an error and returns None. To enable use of this method, a user’s subtype must implement a version that returns the subtype’s wrapper.

For example:

class cmd(UVMObject):
  type_id = None

  @classmethod
  def get_type(cls):
    return cls.type_id.get()

Then, to use:

factory.set_type_override(cmd.get_type(), subcmd.get_type())

This function is implemented by the uvm_*_utils functions, if employed.

Returns:

get_type_name()

This function returns the type name of the object, which is typically the type identifier enclosed in quotes. It is used for various debugging functions in the library, and it is used by the factory for creating objects.

This function must be defined in every derived class.

A typical implementation is as follows:

class mytype (UVMObject):
  ...
  type_name = "mytype"

  def get_type_name(self):
    return my_type.type_name

We define the type_name static variable to enable access to the type name without need of an object of the class, i.e., to enable access via the scope operator, ~mytype::type_name~.

Returns

Type name of the object.

Return type

str

type_id = <uvm.base.uvm_registry.UVMObjectRegistry object>

type_name = 'UVMRelatedLink'