#### IcyIcy

Joined Nov 17, 2012
32
I am not able to do the increment and the testbench for this code.

Question:

A system has a 3-bit input D_IN which is read in at every positive edge of a clock input CLK. If the current D_IN is greater than the previous D_IN by at least 2, a 3-bit output Count is incremented. If D_IN is 0 for 3 consecutive CLK cycles, the count is reset. When Count reaches 6, the system will assert an output Alarm and the Count will not increase further, till it is reset by giving 0s at D_IN for 3 consecutive cycles.

Test case:

Clk 1 2 3 4 5 6 7 8 9 1 0 11 12 13 14 15 16 17 18

D_IN 0 0 0 2 4 7 6 0 2 4 6 3 5 7 0 0 0 0
code

library IEEE;use IEEE.STD_LOGIC_1164.ALL;use IEEE.NUMERIC_STD.ALL;

entity johnson_counter isport(
D_in :instd_logic_vector(2downto0);
alarm utstd_logic;
CLK_I :instd_logic);end johnson_counter;

architecture Behavioral of johnson_counter is

signal xnew, xold, count1, count2:unsigned(2downto0):=(others=>'0');

begin

process(CLK_I)beginif( rising_edge(CLK_I))then
xnew <=std_logic_vector(unsigned(D_in));
xnew <= xnew -"010";if(xnew => xold)then
count1 <= count1 +"1";if(xnew =0)then
count2 <= count2 +"1";if(xnew /=0)then
count2 <="0";if(count2 ="011")then
alarm <="1";endif;endif;endif;endif;endif;endprocess;

#### WBahn

Joined Mar 31, 2012
26,398
So you've made a statement, namely that you can't do your homework. What's your question? More to the point, what have you done to attempt to do your homework?

Joined Sep 20, 2014
54
Bahn some people do not know where to begin.

#### bertus

Joined Apr 5, 2008
21,674
Hello,