HASE User Guide

ENTITY - Architecture Entity Description

Synopsis

The ENTITY construct enables the creation of a basic type of the architecture.

Syntax

ENTITY entity_type_name library_name (
EXTENDS (abstract_type)
DESCRIPTION ("description")
INCLUDE ("compilation options")
STATES (state1, ...)
PARAMS ( modifier reference_parameter, ... )
PORTS ( port, ... ) )

entity_type_name str - The name of the type of entity to be created. This is used to create instances of the component in the architecture, and to identify the correct simulation code and icon.
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 Clocks for a description of components which are currently in the HASE library.
abstract_type str (optional) - The name of the abstract entity from which this entity is intended to inherit. The abstract entity must have previously been defined in the entity library.
description str - A description of an aspect of the entity.
compilation options str (optional) - give additional compilation information for this specific entity. For example, paths to find header files can be specified (e.g. -I${HASEDIR}/distributions/includejava).
statei str (optional) - This is a declaration of the entity's states. It provides the entity with a variable called my_state which can take values declared in the STATES statement. Each state can have a gif images associated with it in the .elf file.
modifier (optional) - There are three possible types of modifier: final; read_only; static.
Using the final modifier means that the value of this parameter is never written to the trace file.
The static modifier must be used when the parameter is to be shared by every instance of this entity.
The read_only modifier is used when a parameter is declared which must not be modified by the user via the gui, the value can be updated only by the instance of the entity. In the example below, the hit parameter is declared read_only. The user cannot decide what the number of hits is.
reference_parameter - This section of the entity definition describes the parameters that are associated with the entity. For example, a memory entity may have an array associated with it to hold the contents, and an integer to hold the access time of the component. Careful selection of the parameters can result in reusable components. For example a cache entity might have parameters for its size, associativity and access time. See the reference section.
port - This section of the entity definition describes the ports of the entity. The ports are the entities means of communicating with the other entities. Ports of different entities are connected together to form a communication link.

Example

`ENTITY Cache`	(
	`DESCRIPTION ( "A generic parameterized cache" )`
	`PARAMS (`
		`RARRAY ( Memory, cache_contents )`
		`RINT ( access_time, 2 )`
		`RENUM ( Associativity, cache_assoc, 0 )`
		`read_only RINT ( hit, 0 )`
		)
	`PORTS (`
		`PORT ( to_cpu, LinkData, SOURCE )`
		`PORT ( from_cpu, LinkData, DESTINATION )`
		`PORT ( to_main_mem, LinkData, SOURCE )`
		`PORT ( from_main_mem, LinkData, DESTINATION )`
		)
	)
`STRUCTURE (`
`AENTITY`	`Cache CACHE1 (`
		`DESCRIPTION ("Level 1 cache")`
		`ATTRIB(RPARAM(clockName,CACHE_CLOCK)`
		)
	)

clockName allows the clock with which this instantiation of the entity is registered to be selected. This only needs to be specified if the clock to be used is a Pll, i.e. not the standard Clock with which an entity is automatically registered through the EXTENDS mechanism. See Clocks for further details.