پاورپوینت کامل Hardware Modeling Verification Basic Elements in VHDL 53 اسلاید در PowerPoint

قسمتی از پاورپوینت :

An identifier can be any length, in other words, as many characters as desired
An identifier is:
XOR2_OP2 and XOr2_Op denote the same identifier.)
The allowed characters are a-z (lowercase letters), A-Z (uppercase letters), 0-9 (numerals), and _ (underscore).
The first character is a letter and the last character must not be underscore.
No adjacent underscore are allowed.
Rules of constructing extended identifiers in VHDL-93 are given:
An extended identifier can be any length, in other words, as many Characters as desired.
An extended identifier must be delimited by leading and trailing backslashes, \(for example, \2XOR_OP\).
The allowed characters are any graphic character. Graphic characters include all the characters allowed for VHDL-93 basic identifiers plus special characters such as “-”, “*”, “A,”, “e”.
Within the enclosing backslashes, graphic characters can appear in any order, except that a backslash used as part of an extended identifier must be denoted by two adjacent backslashes. (For example, XOR\2 is denoted by \XOR\\2\).
An extended identifier is case sensitive, meaning that there is a difference between uppercase and lowercase letters. (For example, \XOR2_OP\ and \XOr2_Op\ denote different identifiers.)
An extended identifier is different from any keyword or basic identifier. Also, the extended identifier \XOR2_OP\ and the basic identifier XOR2_Op do not denote same name.
There are four types of objects in VHDL
Constants
Variables
Signals
Files
The scope of an object is as follows :
Objects declared in a package are available to all VHDL descriptions that use that package
Objects declared in an entity are available to all architectures associated with that entity
Objects declared in an architecture are available to all statements in that architecture
Objects declared in a process are available only within that process