need a help with strange error" left bound of the range must be a constant "

what is the size of r_by_2? if its not a constant, how do you know that both vector sizes are the same?

You could just stick it in a for loop and do it bit by bit.

for i in 0 to r_by_2-1 loop
  q(i) <= q(i+r_by_2);
  q(i+r_by_2) <= q(i);
end loop;

the r_by_2 is

r_by_2 : integer range 0 to m_size_1

I have tried the for loop but its give me another errors

I didnt get it so can you explain more

the problem is I'm modifying this code and trying to break it down into datapath and controller

then Im going to write another code using different numbering system so I need to understand it perfectly

here is more of my code

Reg_P:process (CLK)

begin

if (CLK'event and CLK='1') then

if RESET='1' then

p<= (others => '0');

else

case CS is

-----------------------------------

when S1 =>

p <= X_in;

-----------------------------------

when S7 =>

if (mul_result = '1') then

p <= mul_c;

end if;

-----------------------------------

when S8 =>

p <= t;

-----------------------------------

when S10 =>

p <= p(m_size-2 downto 0) & p(m_size-1);

-----------------------------------

when others =>

null;

-----------------------------------

end case;

end if;

end if;

end process;

-----------------------------------------------

Reg_Q:process (CLK, r_by_2)

begin

if (CLK'event and CLK='1') then

if RESET='1' then

q<= (others => '0');

else

case CS is

-----------------------------------

when S2 =>

q<=p;

-----------------------------------

when S4 =>

if(r_by_2 = 1) then

q <= q (m_size-r_by_2-1 downto 0) & q(m_size-1);

else

q(m_size-1 downto r_by_2) <= q (m_size - r_by_2 - 1 downto 0);

q(r_by_2-1 downto 0) <= q(m_size-1 downto m_size - r_by_2);

end if;

-----------------------------------

when others =>

null;

-----------------------------------

end case;

end if;

end if;

end process;

Unfortunately, important parts are still missing from the code, e.g. definition of all involved signals and generics. So the exact solution can't be given.

The said error message about requiring constant range for bit vector slices is simply reflecting VHDL syntax rules. As mentioned by Tricky, a for loop with a bitwise copy is the usual way to implement assignments of dynamical varying size. A problem you probably stumbled upon is, that the for loop range also must be constant. So you need to do the iteration over the maximal range and decide with an if statement about the actual used range. I'm sure you can figure it out when thinking about it a little bit.

P.S.: I fear, that the construct for i in 0 to r_by_2-1 loop doesn't work for the said reasons. You'll probably need

for i in 0 to msize-1 loop
  if i < r_by_2 then
  end if;
end loop;

when S4 => 
 if(r_by_2 = 1) then
 q <= q (m_size-r_by_2-1 downto 0) & q(m_size-1);
 else
 q(m_size-1 downto r_by_2) <= q (m_size - r_by_2 - 1 downto 0);
 q(r_by_2-1 downto 0) <= q(m_size-1 downto m_size - r_by_2);
 end if;

can be replaced by:

when S4 =>
  for i in 0 to m_size - 1 loop
    q(i0) <= q((i + r_by_2) mod m_size) ;
  end loop ;

This code synthesises (I checked!)

You may want to use a barrel shift/rotate component in stead (especially if m_size is not a power of 2 as the code above then needs dividers to calculate the 'mod' function), it will probably use less resources and certainly run faster.

Please dont thread hijack - start your own thread.

Dont use caps - its like shouting

Please use code tags

line 259 is "count <= count + 1" I dont think this is the line you're talking about.

I have tried what you said and its work

but the problem is that when I do the testbench the results need to be rotated to the lift one time

--- Quote Start ---

when S4 => 
 if(r_by_2 = 1) then
 q <= q (m_size-r_by_2-1 downto 0) & q(m_size-1);
 else
 q(m_size-1 downto r_by_2) <= q (m_size - r_by_2 - 1 downto 0);
 q(r_by_2-1 downto 0) <= q(m_size-1 downto m_size - r_by_2);
 end if;

can be replaced by:

when S4 =>
  for i in 0 to m_size - 1 loop
    q(i0) <= q((i + r_by_2) mod m_size) ;
  end loop ;

This code synthesises (I checked!)

You may want to use a barrel shift/rotate component in stead (especially if m_size is not a power of 2 as the code above then needs dividers to calculate the 'mod' function), it will probably use less resources and certainly run faster.

--- Quote End ---