Predefined attributes

Kind	type
Prefix	any type or subtype T
Result type	base type of T
Restrictions	This attribute can only be used as a prefix for the names of other attributes, e.g., T'BASE'LEFT.

Kind	value
Prefix	any scalar type or subtype T
Result type	same type as T
Result	left bound of T

Kind	value
Prefix	any scalar type or subtype T
Result type	same type as T
Result	right bound of T

Kind	value
Prefix	any scalar type or subtype T
Result type	same type as T
Result	upper bound of T

Kind	value
Prefix	any scalar type or subtype T
Result type	same type as T
Result	lower bound of T

Kind	value
Prefix	any scalar type or subtype T
Result type	boolean
Result	TRUE if T is defined with an ascending range; FALSE otherwise.

Kind	function
Prefix	any scalar type or subtype T
Parameter	expression whose type is the base type of T
Result type	string
Result	The string of the parameter value. Preferably lower case letters are used without additional chars (Exception: Extended Identifier → \ ; Character Literal → `). Physical types are represented with the primary unit, except the type time. There the current resolution limit of the simulator determine the unit. Numbers of type real are represented up to R number right of the decimal point. Unnecessary zeros are left out. The replacement characters of See Replacing characters are not allowed.
Restrictions	The type of the parameter have to be of the subtype of the Prefix.

Kind	function
Prefix	any scalar type or subtype T
Parameter	expression of type string
Result type	base type of T
Result	Value of T whose string representation is X. Additional leading and trailing whitespaces are allowed and ignored. Numerical types are represented as numbers with any valid base. Physical types are represented with any valid unit. The replacement characters of See Replacing characters are allowed.
Restrictions	The parameter have to be a valid string representation of a literal of type T.

Kind	function
Prefix	any discrete or physical type or subtype T
Parameter	expression with a base type of T
Result type	universal_integer
Result	position of the parameter value

Kind	function
Prefix	any discrete or physical type or subtype T
Parameter	expression of an integer type
Result type	base type of T
Result	value of the element whose positional number = X
Restrictions	An error occurs if the result does not belong to the range T'LOW to T'HIGH.

Kind	function
Prefix	any discrete or physical type or subtype T
Parameter	expression whose base type is of the type T
Result type	base type of T
Result	value of the element whose positional number = X+1
Restrictions	An error occurs if X=T'HIGH or if X does not belong to the range T'LOW to T'HIGH.

Kind	function
Prefix	any discrete or physical type or subtype T
Parameter	expression whose base type is of the type T
Result type	base type of T
Result	value of the element whose positional number = X-1
Restrictions	An error occurs if X=T'LOW or if X does not belong to the range T'LOW to T'HIGH.

Kind	function
Prefix	any discrete or physical type or subtype T
Parameter	expression whose base type is of the type T
Result type	base type of T
Result	value of the element which is left of the element which is addressed by X
Restrictions	An error occurs if X=T'LEFT or if X does not belong to the range T'LOW to T'HIGH.

Kind	function
Prefix	any discrete or physical type or subtype T
Parameter	expression whose base type is of the type T
Result type	base type of T
Result	value of the element which is right of the element which is addressed by X
Restrictions	An error occurs if X=T'RIGHT or if X does not belong to the range T'LOW to T'HIGH.

Kind	function
Prefix	any prefix which is suitable as an array object, an alias of it or a conditional array-subtype
Parameter	locally static expression of the type universal_integer whose value must not exceed the dimension of A. If there is no parameter it defaults to 1.
Result type	type of the left bound of the Nth index range of A
Result	left bound of the Nth index range of A

Kind	function
Prefix	any prefix which is suitable as an array object, an alias of it or a conditional array-subtype
Parameter	locally static expression of the type universal_integer whose value must not exceed the dimension of A. If there is no parameter default value 1 is used.
Result type	type of the right bound of the Nth index range of A
Result	right bound of the Nth index range of A

Kind	function
Prefix	any prefix which is suitable as an array object, an alias of it or a conditional array-subtype
Parameter	locally static expression of the type universal_integer whose value must not exceed the dimension of A. If there is no parameter it defaults to 1.
Result type	type of the upper bound of the Nth index range of A
Result	upper bound of the Nth index range of A

Kind	function
Prefix	any prefix which is suitable as an array object, an alias of it or a conditional array-subtype
Parameter	locally static expression of the type universal_integer whose value must not exceed the dimension of A. If there is no parameter it defaults to 1.
Result type	type of the lower bound of the Nth index range of A
Result	lower bound of the Nth index range of A

Kind	range
Prefix	any prefix which is suitable as an array object, an alias of it or a conditional array-subtype
Parameter	locally static expression of the type universal_integer whose value must not exceed the dimension of A. If there is no parameter it defaults to 1.
Result type	type of the Nth index range of A
Result	The range A'RIGHT(n) to A'LEFT(n) for a rising or A'RIGHT(n) downto A'LEFT(n) for a descending direction of the Nth index range of A.

Kind	range
Prefix	any prefix which is suitable as an array object, an alias of it or a conditional array-subtype
Parameter	locally static expression of the type universal_integer whose value must not exceed the dimension of A. If there is no parameter it defaults to 1.
Result type	type of the Nth index range of A
Result	The range A'RIGHT(n) downto A'LEFT(n) for a rising or A'RIGHT(n) to A'LEFT(n) for a descending direction of the Nth index range of A.

Kind	value
Prefix	any prefix which is suitable as an array object, an alias of it or a conditional array-subtype
Parameter	locally static expression of the type universal_integer whose value must not exceed the dimension of A. If there is no parameter it defaults to 1.
Result type	universal_integer
Result	number of values in the Nth index range

Kind	value
Prefix	any prefix which is suitable as an array object, an alias of it or a conditional array-subtype
Parameter	locally static expression of the type universal_integer whose value must not exceed the dimension of A. If there is no parameter it defaults to 1.
Result type	boolean
Result	TRUE if the Nth index range of A is defined with an ascending range; FALSE otherwise.

Kind	signal
Prefix	any signal
Parameter	Static expression of the type TIME which provides a value > 0. If t is missing the it defaults to 0.
Result type	base type of S
Result	a signal delayed by t time units, equivalent to S

Kind	signal
Prefix	any signal
Parameter	Static expression of the type TIME which provides a value > 0. If t is missing the it defaults to 0.
Result type	boolean
Result	A signal which has the value TRUE if there has been no event at S for t time units; otherwise it has the value FALSE.

Kind	signal
Prefix	any signal
Parameter	Static expression of the type TIME which provides a value > 0. If t is missing the it defaults to 0.
Result type	boolean
Result	A signal that has the value TRUE when S has been quiet for t time units; otherwise it has the value FALSE.

Kind	signal
Prefix	any signal
Result type	bit
Result	A signal whose value is inverted in each simulation cycle in which the signal S is activated.
Restrictions	A description must not depend on the initial value of S'TRANSACTION.

Kind	function
Prefix	any signal
Result type	boolean
Result	A signal which has the value TRUE when there has been an event at S in the current simulation cycle; otherwise it has the value FALSE

Kind	function
Prefix	any signal
Result type	boolean
Result	A signal which has the value TRUE when S is active in the current simulation cycle; otherwise it has the value FALSE.

Kind	function
Prefix	any signal
Result type	time
Result	The amount of time that has passed since the last event occurred on signal S.

Kind	function
Prefix	any signal
Result type	time
Result	The amount of time that has passed since S last was active.

Kind	function
Prefix	any signal
Result type	base type of S
Result	The value of S immediately before the last change

Kind	function
Prefix	any signal
Result type	boolean
Result	S = scalar: FALSE if the current value of the driver of S in the current process is determined by the null transaction; TRUE otherwise. S = composite: TRUE if for every subelement R of S R'DRIVING is TRUE. FALSE otherwise. S = null slice: S'DRIVING=TRUE.
Restrictions	This attribute is available only from within a process, a concurrent statement with an equivalent process or a subprogram. Is S a port then the port must have the mode inout, out or buffer. If the attribute name appears in a subprogram body then it have to be a declarative item contained within a process statement and S have to be a formal parameter of the given subprogram or of a parent of that subprogram. The formal parameter of the subprogram has then to be of mode inout or out.

Kind	function
Prefix	any signal
Result type	base type of S
Result	S = scalar: Current value of the driver of S in the current process S = composite: Corresponding aggregate. S = null slice: null slice.
Restrictions	This attribute is available only from within a process, a concurrent statement with an equivalent process or a subprogram. Is S a port then the port must have the mode inout, out or buffer. If the attribute name appears in a subprogram body then it have to be a declarative item contained within a process statement and S have to be a formal parameter of the given subprogram or of a parent of that subprogram. The formal parameter of the subprogram has then to be of mode inout or out. S'DRIVING has to be TRUE at the time S'DRIVING_VALUE is evaluated.

Kind	value
Prefix	any named entity (see See Attribute specification)
Result type	string
Result	The simple name, character literal or operator symbol of the named entity, without leading or trailing whitespace or quotations marks. (Exception: character literal → ' and extended identifier → \). Except for extended identifiers lower case characters are used.

Kind	value
Prefix	any named entity (see See Attribute specification)) other then the local ports and generics of a component declaration.
Result type	string
Result	The complete hierarchical path including instantiated entities beginning at the current level downto the name object.

Kind	value
Prefix	any named entity (see See Attribute specification)) other then the local ports and generics of a component declaration.
Result type	string
Result	The complete hierarchical path excluding instantiated entities beginning at the root level downto the name object.

Kind	value
Prefix	any block or entity architecture
Result type	boolean
Result	A value which is TRUE if the block or respectively the architecture contains no component instantiation; otherwise the value is FALSE.

Kind	value
Prefix	any block or entity architecture
Result type	boolean
Result	A value which is TRUE if the block or respectively the architecture contains neither a passive process statement nor a concurrent statement with a corresponding process statement; otherwise the value is FALSE.

Predefined attributes

T'BASE

T'LEFT

T'RIGHT

T'HIGH

T'LOW

T'ASCENDING

T'IMAGE(X)

T'VALUE(X)

T'POS(x)

T'VAL(x)

T'SUCC(x)

T'PRED(x)

T'LEFTOF(x)

T'RIGHTOF(x)

A'LEFT[(n)]

A'RIGHT[(n)]

A'HIGH[(n)]

A'LOW[(n)]

A'RANGE[(n)]

A'REVERSE_RANGE[(n)]

A'LENGTH[(n)]

A'ASCENDING[(n)]

S'DELAYED[(t)]

S'STABLE[(t)]

S'QUIET[(t)]

S'TRANSACTION

S'EVENT

S'ACTIVE

S'LAST_EVENT

S'LAST_ACTIVE

S'LAST_VALUE

S'DRIVING

S'DRIVING_VALUE

E'SIMPLE_NAME

E'INSTANCE_NAME

E'PATH_NAME

B'BEHAVIOUR (VHDL'87 only)

B'STRUCTURE (VHDL'87 only)

VHDL-Online