session five

http://www.bized.co.uk

Copyright 2006 – Biz/ed

Prepared by Alaa Salah Shehata Mahmoud A. M. Abd El Latif Mohamed Mohamed Tala’t Mohamed Salah Mahmoud

Version 02 – October 2011

Session 5



-Data Types

-Scalar

-Composite

-User defined

-LABs

-Memory units

5 Contents

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Session 5

Data Types

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-Type declaration is made inside architecture declaration, entity declaration,

process declaration

-VHDL is a strongly typed language, meaning that data objects of different types

cannot be assigned to one another without the use of a type conversion function.

Data Types can be classified into:

1–Scalar types

Refers to all types whose objects have a single value at any time instant.

2–Composite types

Refers to types that have a regular structure consisting of elements of the same type

such as array or elements of different types such as record.

3–User defined types

Types that are defined by default and to be defined by the user before using.

Session 5

Data Types

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-Refers to all types whose objects have a single value at any time instant.

Scalar Types

1-Enumerated types

a–Bit

b–Boolean

c–Character

d-String

2–Integer

3–Floating Point

4–Physical types

Session 5

Data Types 1-Scalar Types

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-Specifies list of possible values

a-Bit

Type bit defines two standard logical values (‘0’ , ‘1’) bit ( „0‟ , „1‟ ) ;

b-Boolean

Type Boolean is used in the conditional operations boolean ( false , true ) ;

Logical functions such as equality (=) and comparison (<) functions return a BOOLEAN value. Example: Evaluate the following relational expression:

”1011” < ”110”. Comment!

The expression evaluates to true.

Session 5

Data Types 1-1 Enumerated Types

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c-Character

covers all characters character ( „@‟,‟#‟, …. „A‟ , „B‟, ...) ; The CHARACTER data

type enumerates the ASCII character set. D- string if we need to write string of characters we use this key word

Session 5

Data Types 1-1 Enumerated Types

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Session 5

Example 22

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Enumerated Types



entity ex_enum is

Port ( inp1 : in STD_LOGIC;

inp2 : in STD_LOGIC;

outp1 : out Boolean;

outp2 : out Character;

outp3 : out string(1 to 5)

);

end ex_enum;

architecture Behavioral of ex_enum is

begin

outp1 <= true when inp1 < inp2 else false ;

outp2 <= „t‟ when inp1 < inp2 else „f‟ ;

outp3 <= “equal” when inp1=inp2 else “notEQ”;

end Behavioral;

Session 5

Example 1-1 Enumerated Types

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integer range -2147483648 to 2147483648 ;

Example Signal counter : integer range 0 to 15 ;

Note

The implementation of the type integer in the synthesis and depends on the range

specified by the user.

Session 5

Data Types 1-2 Integer Type

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Session 5

Example 23

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Integer Type



Session 5

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PROCESS (X)

variable a: integer;

variable b: integer range 0 to 15;

type int is range -10 to 10;

variable d: int;

BEGIN

a := 1;

b := -1; d := -12;

a := 1.0;

a := -1; b := 10;

d := a;

END PROCESS;

integer Types



It has no meaning in synthesis so it is only used for simulation.

Named as floating or real type -1.0E308 to 1.0E308

Session 5

Data Types 1-3 Floating Point Type

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They must converted to bits at synthesize time.



Session 5

Example 24

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Floating Point Type



entity ex_enum is

Port ( inp1 : in STD_LOGIC;

inp2 : in STD_LOGIC;

outp : out real

);

end ex_enum;

architecture Behavioral of ex_enum is

begin

outp<= 1.5 when inp1 < inp2 else 2.5;

end Behavioral;

Session 5

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Floating Point Type



Physical types represent measurements of some quantity

Allows to define measurements of some physical quantities such as time, length,

resistance…

Syntax type <type_name> is range <range>

units

<primary_unit>;

<secondary_unit> =

<integer> <primary_unit>;

…

end units;

<primary_unit> an identifier for the primary unit of measurement for that type

<secondary_unit> an integer multiple of the primary unit

Session 5

Data Types 1-4 Physical Type

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Predefined physical types

time type Time is the only predefined physical type

Example type time is range -2147483647 to 2147483647

units

fs;

ps = 1000 fs;

ns = 1000 ps;

us = 1000 ns;

ms = 1000 us;

sec = 1000 ms;

min = 60 sec;

hr = 60 min;

end units;

Note physical types are not synthesizable

Session 5

Data Types 1-4 Physical Types

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Composite Types

1–Array

Multiple elements of the same type

2-Record

Multiple elements of different types

Session 5

Data Types 2-Composite Types

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•Group elements of the same type Syntax

Type <type_name> is array <range> of <data_type>;

Example

1D array type data is array (7 downto 0) of bit ;

signal D_bus : data ;

D_bus <= “10101010” 2 D array type memory is array (0 to 15) of std_logic_vector(7 downto 0);

signal word : memory ;

word (5) <= “10010110” ;

word (15,4) <= „1‟ ;

Session 5

Data Types 2-1 Array

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.

.

.

0 1 2 7 0

1

15



type word is array (0 to 31) of std_logic;

type byte is array (7 downto 0) of std_logic;

type memory is array (0 to 15) of std_logic_vector(7 downto 0);

signal D_bus : word;

signal mem1 : memory;

variable x : byte;

variable y : std_logic;

mem1 (5) <= "10010110" ;

mem1 (15,4) <= '1' ;

y := x(5);

Session 5

Data Types 2-1 Array

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Group elements of possibly different types

Elements are indexed via field names

Syntax type <type_name> is record

identifier: type;

identifier: type;

…

end record;

Session 5

Data Types 2-2 Record

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Example Data Packet

type packet is record

ID : integer range 0 to 15 ;

C : std_logic ;

SOF : std_logic_vector(7 downto 0) ;

PAYLOAD : std_logic_vector( 127 downto 0) ;

CRC : std_logic_vector(3 downto 0) ;

EOF : std_logic_vector(7 downto 0);

end record ;

signal tx_packet : packet;

tx_packet.ID <= 3 ;

tx_packet.PAYLOAD <= “1000………………..10101”;

Session 5

Data Types 2-2 Record

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Types that are defined by default and to be defined by

the user before using, such as encoding FSM next and

present states.

Syntax: Type <type_name> is (value1, value2, …)

Most often used in the encoding of FSM states. When encoding the states of the FSM of the control unit

in a microprocessor, one can define it as follows.

Type states is (reset, fetch, decode, excute, store)

Signal P_state : states;

Session 5

Data Types 3-User Defined Types

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Session 5

Data Types 3-User Defined Types

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VHDL is a strongly typed language, meaning that data objects of different types cannot be

assigned to one another without the use of a type conversion function.

If A and B are both integer variables, the assignment

a := b + ‘1’ ; is illegal because ‘1’ is of type bit.

For Example

SIGNAL a,b : IN integer;

SIGNAL y : OUT STD_LOGIC_VECTOR (7 DOWNTO 0);

...

y <= CONV_STD_LOGIC_VECTOR ((a+b), 8); to change from integer to std_logic

or a<=conv_integer(y); to change from std_logic to integer

Session 5

Data Types -Data Conversion

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Session 5

Memories

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first you have to think about entity (I/p &o/P)

1-clock for synchronization

2-write enable to control writing the data on memory , RAM<= data_in.

3-read enable to control read date from memory ,data_out <= Ram.

4 address to control which data you want to read or write .

5- input data and output data

Session 5

Data Types -How to make RAM

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the question is do we have to but reset as input ???



• RAM

with separate read and write ports

28

Session 5

lab 9



• RAM

with internal address control

29

Session 5

lab 10



• ROM

Make Synchronous 16 X 8 ROM

30

Session 5

lab 11



Mini Project-2

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Session 2



1) One purpose of scrambling is to

reduce the length of strings of zeros or

ones in a transmitted signal, since a

long string of 0s or 1s may cause

transmission synchronization problems,

i.e. cause the clock regeneration at the

receiver more difficult.

2) Also for making the transmitted signal more secured.

Session 5

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Why Scrambler



B(i)=[A(i)+c(i)]mod2 A(i) is the input to the scrambler. B(i) is the scrambled code word (the output of the scrambler) c(i) is the output of the Pseudo-random sequence generation

Session 5

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Scrambler A(i) B(i)

Scrambler



Pseudo-random sequence generation

As we said before, C(i) will be Xored with the input of the

scrambler b(i) generating the scrambled output B(i).

B(i)=[b(i)+c(i)]mod2

Session 5

Scrambler

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Questions

Session-5

35

Session 5



Take Your Notes Print the slides and take your notes here

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Session 5

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See You Next Session

Session 5

37

session five

Technology

physical types

typestype declaration

types1scalar types

elements of different

scalar typesrefers

data typescontents scalar

user defined typestypes

entity declaration