An entity declaration defines input to a model, outputs supported by the model, and generic parameters used by the different implementations of the model.

ENTITY entity_name IS

GENERIC (generic_list); -- optional generic list

PORT (port_list); -- input/output signal ports

END [ENTITY] name;

generic_list

Specifies static information to be communicated to a model from its environment for all architectures. These include timing information (setup, hold, delay times), ambient information (temperature), and other parameters.

port_list

Specifies dynamic information to be communicated between a model and its environment for all architectures. A port can be represented by a quantity, terminal, or signal. The mode of a port defines the directions of the signals on that port, and is one of IN, OUT, INOUT, BUFFER, or LINKAGE.

Port Modes

An IN port can be read but not updated within the module. An IN port cannot appear on the left side of a signal assignment.

An OUT port can be updated but not read within the module. An OUT port cannot appear on the right side of a signal assignment.

An INOUT port is bidirectional and can be both read and updated, with multiple update sources possible.

Signal objects can use the mode IN, OUT, and INOUT; quantity objects can use IN and OUT whereas terminals have no direction mode.

Ports of type BUFFER and LINKAGE are transformed to INOUT types in Twin Builder.

ENTITY spring_tr IS

GENERIC(s0: DISPLACEMENT:= 0.0); -- list of generic parameters

PORT(QUANTITY c: IN STIFFNESS:= 100.0; -- list of quantity ports

TERMINAL tr1, tr2 : TRANSLATIONAL_V; -- list of terminal ports

SIGNAL ctrl: IN BIT); -- list of signal ports

END ENTITY spring_tr;