Synchronous 4 Bit Up counter

VHDL Code:


library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use ieee.std_logic_unsigned.all;

entity sync_counter is
port(clk,rst,input: in std_logic;
     q : out std_logic_vector(3 downto 0));
end sync_counter;

architecture Behavioral of sync_counter is
signal count : std_logic_vector(3 downto 0);
begin

process (clk,rst,input)

begin

if(rst='0') then
count<="0000";
elsif(clk'event and clk='1') then
if(input='1') then
count<=count + 1;
end if;
end if;
end process;
q<=count;

end Behavioral;

Simulated waveform:

Asynchronous Up counter using T- Flipflop

Three-bit counter capable of counting from 0 to 7. The clock inputs
of the three flip-flops are connected in cascade. The T input of each flip-flop is connected
to a constant 1, which means that the state of the flip-flop will be reversed (toggled) at each
positive edge of its clock. We are assuming that the purpose of this circuit is to count the
number of pulses that occur on the primary input called Clock. Thus the clock input of
the first flip-flop is connected to the Clock line. The other two flip-flops have their clock
inputs driven by the Q output of the preceding flip-flop. Therefore, they toggle their state
whenever the preceding flip-flop changes its state from Q = 1 to Q = 0, which results in a
positive edge of the Q signal.

VHDL Code:

 

entity up_counter is
port(input,clk,rst: in std_logic;
     q: inout std_logic_vector(2 downto 0));
end up_counter;

architecture Behavioral of up_counter is

component t_ff is
port(clk,rst,t: in std_logic;
     q,qbar: inout std_logic);
end component;

signal w1,w2,w3 : std_logic;

begin

x1: t_ff port map (clk=>clk,rst=>rst,t=>input,q=>q(0),qbar=>w1);
x2: t_ff port map (clk=>w1,rst=>rst,t=>input,q=>q(1),qbar=>w2);
x3: t_ff port map (clk=>w2,rst=>rst,t=>input,q=>q(2),qbar=>w3);

end Behavioral;

Note: The T-Flipflop program is posted previously add that to the source.

What is Binary?

Binary describes a numbering scheme in which there are only two possible values for each digit: 0 and 1. The term also refers to any digital encoding/decoding system in which there are exactly two possible states. In digital data memory, storage, processing, and communications, the 0 and 1 value are sometimes called "low" and "high," respectively.

Discrete elements of information are represented in a digital system by physical quantities called signals. Electrical signals such as voltages and currents are the most common. Electronic devices called Transistors predominate in the circuitry that implements these signals. The signals in most present‐day electronic digital systems use just two discrete values and are therefore said to be binary. A binary digit, called a bit, has two values: 0 and 1. Discrete elements of information are represented with groups of bits called binary codes. For example, the decimal digits 0 through 9 are represented in a digital system with a code of four bits (e.g., the number 7 is represented by 0111).

Since binary is a base-2 system, each digit represents an increasing power of 2, with the rightmost digit representing 20, the next representing 21, then 22, and so on. To determine the decimal representation of a binary number simply take the sum of the products of the binary digits and the powers of 2 which they represent. For example, the binary number 100101 is converted to decimal form as follows:

1001012 = [ ( 1 ) × 25 ] + [ ( 0 ) × 24 ] + [ ( 0 ) × 23 ] + [ ( 1 ) × 22 ] + [ ( 0 ) × 21 ] + [ ( 1 ) × 20 ]

1001012 = [ 1 × 32 ] + [ 0 × 16 ] + [ 0 × 8 ] + [ 1 × 4 ] + [ 0 × 2 ] + [ 1 × 1 ]

1001012 = 3710

Octal number

The conversion from binary to octal is easily accomplished by partitioning the binary number into groups of three digits each, starting from the binary point and proceeding to the left and to the right.

Hexadecimal

Conversion from binary to hexadecimal is similar, except that the binary number is divided into groups of four digits:

Let us see the tabular column comparison to decimal number to its binary number, octal, hexadecimal.