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[SOLVED] help:make the clock divider twice as fast or 2 Hz.

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saUNT

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Hello, I hope you guys doing well.
This is one part of a school project, I did the other parts but I'm stuck on this one:

"This given module take the 50 MHz clock_50 of the DE2 board and divides down to generate a CLKout of 1 Hz. Modify this given module to make the clock twice as fast or 2 Hz"

and here is the code:
Code VHDL - [expand]
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library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;
 
entity DIVIDER is
port ( CLKin: in std_logic;
reset: in std_logic;
CLKout: out std_logic);
end DIVIDER;
 
architecture behavioral of DIVIDER is
signal count: integer:=0;
signal temp : std_logic := '1';
begin
process(CLKin,count,reset)
begin
if(reset='1') then count<=0; temp<='1';
elsif(CLKin'event and CLKin='1') then count <=count+1;
if (count = 25000000) then temp <= NOT temp; count<=0;
end if;
end if;
CLKout<= temp;
end process;
end behavioral;
 
Last edited by a moderator:

What exactly is the problem (apart from the fact that clock dividers like this are bad practice)?
 

The teacher is wanting to "Modify this given module to make the clock twice as fast or 2 Hz" but i really don't understand what he is asking
 

if (count = 25000000) then temp <= NOT temp; count<=0;

just make the value half, problem solved
 
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    saUNT

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The original code has a very common bug. "count" will go from 0 to 25000000 and then start from zero again. That is a 25000001 cycle interval, so the frequency divisor is 50000002, not 50000000.

Also, "count" as an integer without range will probably synthesize to 32 bits. I doubt that the synthesis tool is smart enough to reduce it to 25 bits, which is enough. Either put a range on "count", or define it as "unsigned" with the correct size.
 

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