Data types.md

###Standard logic

• Expands the definition of bit to enchance simulation and syntehsis
• Provides signal resolution capability
• Conforms to IEEE Standard 1164

Requires

library ieee;
use ieeee.std_std_logic_1164.all

values

• U: unitnitalied
• X: Forcing Unknown
• 0: Forcing 0
• 1: Forcing 1
• Z: High Impedance
• W: Weak unknown
• L: Weaj 0
• H: Weak 1
• _ Don't care

Scalar

enumerated

• bit
• std_logic
• boolean
• charater

Numeric

• integer
• real

Araay types

• bit vector: "1101" "001001110"

• std_logic_vector

• string

• collections

• files

constant delcarations

constant rfer_fwef: std_logic_vector(6 downto 0) := "100010":

constant ACTIVE: std_logic := '1';

Aritmetic operatios

logical operators

Relationsal Operators

• =
• /= - NOT EQUAL

shift operators

• sll

concantenation operator

signal myNibble:  std_logic_vector(3 downto 0);
signal myByte01:  std_logic_vector(7 downto 0);
signal myByte02:  std_logic_vector(7 downto 0);

myNibble <= "01" & '1' & '0';
myByte01 <= "011" & myNibble & '1';
myByte02 <= "11" & myNibble(2 downto 1) & myByte01(7 downto 4);

range constriant: When using a datatype

class problem: Busses

signal dataBus:  std_logic_vector(31 downto 0); 
signal highLowBytes: std_logic_vector(15 downto 0); 
signal highByte: std_logic_vector(7 downto 0); 
signal lowByte: std_logic_vector(7 downto 0);     
signal statusBits:  
signal oddBit:      
signal signBit:   
std_logic_vector(7 downto 0); 
std_logic_vector(1 downto 0); std_logic; std_logic;

highbyte <= databus(31 downto 24);
lowbyte <= databus(7 downto 0);
oddbyte <= databus(31);
signbit <= databus(31);

highlowbtye <= hightbyte & lowbyte;