VHDL Tutorial

Character types in VHDL
Introduction
Fundamental concepts
Modelling concepts
Elements of behaviour
Elements of structure
Analysis elaboration
Lexical elements
Identifiers
Numbers
Characters and strings 
Syntax descriptions
Constants and variables
Scalar type
Integer types
Floating point types
Time type
Enumeration types
Character types

Boolean type 
Bits type
Standard logic
Sequential statements
Case statements
Loop and exit statements
Assertion statements
Array types & array operations
Architecture bodies
Entity declarations
Behavioral descriptions 
Wait statements
Delta delays
Process statements
Conditional signal assignment 
Selected signal assigment
Structural descriptions
Library and library clauses
Procedures
Procedure parameters
Signal parameters
Default values
Unconstrained array parameter
Functions
Package declarations and bodies
Subprograms in package
Use clauses
Resolved signals and subtypes
Resolved signals and ports
Parameterizing behavior
Parameterizing structure


.

Characters

 

The predefined  enumeration type  character includes  all of the  characters in the  ISO

8859 Latin-1 8-bit character set.   The type definition is shown in Figure 3-2.   It con- taining a mixture of identifiers (for control characters) and character literals (for graph-

ic characters).  The character at position 160 is a non-breaking space character, distinct from the ordinary space character, and the character at position 173 is a soft hyphen.

 

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FIGURE 3-2

 

type character is (

nul,

soh,

stx,

etx,

eot,

enq,

ack,

bel,

bs,

ht,

lf,

vt,

ff,

cr,

so,

si,

dle,

dc1,

dc2,

dc3,

dc4,

nak,

syn,

etb,


 

Characters

 

The predefined  enumeration type  character includes  all of the  characters in the  ISO

8859 Latin-1 8-bit character set.   The type definition is shown in Figure 3-2.   It con- taining a mixture of identifiers (for control characters) and character literals (for graph-

ic characters).  The character at position 160 is a non-breaking space character, distinct from the ordinary space character, and the character at position 173 is a soft hyphen.

 

FIGURE 3-2

 

type character is (

nul,

soh,

stx,

etx,

eot,

enq,

ack,

bel,

bs,

ht,

lf,

vt,

ff,

cr,

so,

si,

dle,

dc1,

dc2,

dc3,

dc4,

nak,

syn,

etb,


 

Scalar Types

 

 

 

 

 

 

 

 

21

 

 

can,

 

em,

 

sub,

 

esc,

 

fsp,

 

gsp,

 

rsp,

 

usp,

 

 

' ',

'!',

'"',

'#',

'$',

'%',

'&',

''',

 

 

'(',

')',

'*',

'+',

',',

'',

'.',

'/',

 

 

'0',

'1',

'2',

'3',

'4',

'5',

'6',

'7',

 

 

'8',

'9',

':',

';',

'<',

'=',

'>',

'?',

 

 

'@',

'A',

'B',

'C',

'D',

'E',

'F',

'G',

 

 

'H',

'I',

'J',

'K',

'L',

'M',

'N',

'O',

 

 

'P',

'Q',

'R',

'S',

'T',

'U',

'V',

'W',

 

 

'X',

'Y',

'Z',

'[',

'\',

']',

'^',

'_',

 

 

'`',

'a',

'b',

'c',

'd',

'e',

'f',

'g',

 

 

'h',

'i',

'j',

'k',

'l',

'm',

'n',

'o',

 

 

'p',

'q',

'r',

's',

't',

'u',

'v',

'w',

 

 

'x',

'y',

'z',

'{',

'|',

'}',

'~',

del,

 

 

c128,

c129,

c130,

c131,

c132,

c133,

c134,

c135,

 

 

c136,

c137,

c138,

c139,

c140,

c141,

c142,

c143,

 

 

c144,

c145,

c146,

c147,

c148,

c149,

c150,

c151,

 

 

c152,

c153,

c154,

c155,

c156,

c157,

c158,

c159,

 

 

' ',

'',

'',

'',

'',

'',

'',

'',

 

 

'',

'',

'',

'',

'',

'-',

'',

'',

 

 

'',

'',

'',

'',

'',

'',

'',

'',

 

 

'',

'',

'',

'',

'',

'',

'',

'',

 

 

'',

'',

'',

'',

'',

'',

'',

'',

 

 

'',

'',

'',

'',

'',

'',

'',

'',

 

 

'',

'',

'',

'',

'',

'',

'',

'',

 

 

'',

'',

'',

'',

'',

'',

'',

'',

 

 

'',

'',

'',

'',

'',

'',

'',

'',

 

 

'',

'',

'',

'',

'',

'',

'',

'',

 

 

'',

'',

'',

'',

'',

'',

'',

'',

 

 

'',

'',

'',

'',

'',

'',

'',

'');

 

 

The definition of the predefined enumeration type character.

 

To illustrate the use of the character type, we declare variables as follows:

 

variable cmd_char, terminator : character;

 

and then make the assignments

 

cmd_char := 'P';

terminator := cr;

 

               
               
               


 

 

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