VHDL Programming

Configurations 201

FOR shifter

FOR A1 : alu USE CONFIGURATION WORK.alu_con;

END FOR;

FOR shift_reg

FOR R1 : int_reg USE CONFIGURATION WORK.int_reg_con;

END FOR;

END FOR;

END FOR;

END FOR;

END cpu_con;

In the configuration cpu_conof entity cpu, architecture fragmentis

used for the entity. Inside of block reg_array, all (R1through R4) of the

int_regcomponents use configuration int_reg_con. In block shifter,

the alucomponent (A1) uses configuration alu_con. For block shift_reg

inside of block shifter, the int_reg component uses configuration

int_reg_con.

Architecture Configurations

The last type of configuration we discuss is the architecture configuration.

This configuration exists in the architecture declarative region and

specifies the configurations of parts used in the architecture. If this type

of configuration is used, a separate configuration declaration is not

needed to configure the components used in the architecture.

The next example configuration is for a very high-level description of an

autopilot. The autopilot block diagram is shown in Figure 7-5. Following

is an example of this type of configuration:

PACKAGE ap IS

TYPE alt IS INTEGER RANGE 0 TO 50000;

TYPE hdg IS INTEGER RANGE 0 TO 359;

TYPE vdir IS INTEGER RANGE 0 TO 9;

TYPE hdir IS INTEGER RANGE 0 TO 9;

TYPE control IS INTEGER RANGE 0 TO 9;

END ap;

USE WORK.ap.ALL;

ENTITY autopilot IS

PORT( altitude : IN alt;

altitude_set : IN alt;

heading : IN hdg;

heading_set : IN hdg;

rudder : OUT control;