Chapter 10 - VHDL Introduction-2x2(1)

expressionn after delay time when others to write a

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Unformatted text preview: = expression1 [after delay-time] when choice1, expression2 [after delay-time] when choice2, ... [expression_n [after delay-time] when others]; To write a complete VHDL module, we must declare all of the input and output signals using an entity declaration, and then specify the internal operation of the module using an architecture declaration. Section 10.3 (p. 292) Figure 10-9: Figure 10-8: VHDL Module with Two Gates VHDL Program Structure Each entity declaration includes a list of interface signals that can be used to connect to other modules or to the outside world. We will use entity declarations of the form: entity entity-name is [port(interface-signal-declaration);] end [entity] [entity-name]; Here is an example of a port declaration that indicates A and B are input signals of type integer that are initially set to 2, and C and D are output signals of type bit that are initialized by default to ‘0’: port(A, B: in integer : = 2; C, D: out bit); The items enclosed in brackets are optional. The interfacesignal-declaration normally has the following form: list-of-interface-signals: mode type [: = initial-value] {; list-of-interface-signals: mode type [: = initial-value]}; Associated with each entity is one or more architecture declarations of the form architecture architecture-name of entity-name is [declarations] begin architecture body end [architecture] [architecture-name]; In the declarat...
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This document was uploaded on 03/16/2014 for the course EE 316 at University of Texas.

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