ABSTRACT - Abstract Entity Definition.

Syntax

ABSTRACT name library_name (
DESCRIPTION ( "description" )
INTERFACE ( SERVICE ( service_name1 , param1, ...) , ... )
PARAMS ( reference_parameters, ...)
)

Synopsis

• name str - The name of the abstract entity.
  
  
• library_name str (optional) - The name of library from which the behaviour is coming from. If the library_name is not specified, then the user must provide a .hase description of the behaviour. See library components for a description of components which are currently in the HASE library.
  
  
• description str - The description of the abstract entity.
  
  
• service_nameX str - The name of a service to be defined by the inheriting entity.
  
  
• paramX str (optional) - Services may have some parameters. In that case, the service name is followed by a comma and a list of parameters separated by a comma. Each parameter must have a type followed by a name. Ex: SERVICE (tick, int no) defines the service tick with one integer parameter named no. The .hase description will be able to use the parameter 'no'. The abstract entity description must call the service tick with an integer parameter. Ex: tick(12);
  
  
• reference_parameter - This section of the abstract definition describes the parameters that are associated with the abstract entity. These parameters will be inherited by the inheriting concrete class (see entity). For example, a memory entity may have an array associated with it to hold the contents, and integer to hold the access time of the component. Careful selection of the parameters could result in reusable components. For example a cache entity might have parameters for its size, associativity and access time. See the reference section.

Example

As an example, the abstract entity clocked has been declared in the tomasulo project.

ENTITYLIB (
ABSTRACT clocked (
DESCRIPTION ("two phases clock entities")
INTERFACE(
SERVICE (pre)
SERVICE (phase0)
SERVICE (phase1)
)
)

This means that the abstract clocked entity declares the pre, phase0 and phase1 services. Those services have to be defined in the concrete entities which will inherit from clocked

Then, one can define concrete entities which claims they define that interface and they want to inherit the body behaviour.
This can be done in an entity declaration by adding the field EXTENDS (clocked). All entities which inherits from an abstract class must define a label for each service declared by the abstract class. This label marks the beginning of the code corresponding to this service. However, these entities must not define a body label as it will be inherited from the abstract class.

With the previous example, the rsc entity declaration of the tomasulo project may be declared as following :

ENTITY rsc (
EXTENDS (clocked)
DESCRIPTION ("Reservation Station Control Register")
PARAMS (
RENUM(rsc_state, cur_state, 0)
RSTRING (FUNC, "FREE")
)
PORTS (
PORT (input, l_con, DESTINATION)
PORT (output, l_con, SOURCE)
)
)


Actually, all the following entities may inherits from clocked : source, flb_reg, flos, decoder, cdb, sdb_reg, fp_reg, rs_opr, rsc, add_res, mul_res, add, mul.

Now let us have a look at an example of .hase code for an abstract entity (here clocked.hase). Note that the pre, phase0 and phase1 code is not defined here, it will be asbtract and will be defined by the concrete classes :

$class_decls int ClockPhase; int DONE; //clock reference sim_entity_id clk; $startup clk = sim.get_entity_id("CLOCK"); ((clock *)sim.get_entity(clk))->registering(get_id()); $body pre(); DONE = 1; // predicate sim_from_p start(clk); while (1) { sim_wait_for(start, ev); SIM_CAST(int, ClockPhase, ev); //to avoid memory leakage if (ClockPhase == 0) // First phase of clock phase0(); else // Second phase of clock phase1(); sim_schedule( clk, 0.0, CLOCK, SIM_PUT(int, DONE)); }

clocked.hase

As an example of concrete class, let us have a look at the rsc.hase code:

$class_decls //entity references sim_entity_id bus; sim_entity_id add_res; sim_entity_id mul_res; //structures and variables t_rs_control Instruction, Register; int RS_no; int output_to_au; //methods void Output_to_au(); $class_defs void rsc::Output_to_au() { // Invoked by a Reservation Station: set output_to_au = 1 output_to_au = 1; } $pre bus = sim.get_entity_id("CDB"); add_res = sim.get_entity_id("ADD_RES"); output_to_au = 0; cur_state = RSC; strcpy(FUNC, "FREE"); dump_state(); $phase0 // predicate sim_from_port receive(input); sim_hold(5); // If there is an event from the CDB, copy function and tag number // into Register. if (sim_waiting(ev, receive) > 0) { SIM_CAST(t_rs_control, Instruction, ev); Register.instrn = Instruction.instrn; Register.tag_no = Instruction.tag_no; if (Register.instrn.function == VOID) strcpy(FUNC, "FREE"); else if (Register.instrn.function == ADD) strcpy(FUNC, "ADD"); else if (Register.instrn.function == SUB) strcpy(FUNC, "SUB"); else if (Register.instrn.function == MUL) strcpy(FUNC, "MUL"); else if (Register.instrn.function == DIV) strcpy(FUNC, "DIV"); dump_state(); } $phase1 // if output_to_au is set, send content of register to arithmetic unit if (output_to_au == 1) { send_CONTROL(output, Register); output_to_au = 0; }

rsc.hase