I am trying to work on inserting if else to loop but it is still expecting some syntax. I cant figure out why this if/else statement wont compile. I am new to VHDL, please help. This is one of the steps along the way and i am stuck.
variable i : integer := 0;
begin
while i < 10 loop
report "i=" & integer'image(i);
i := i + 1;
if i = 6 then
report "okay good job";
else i = 5 then
report " okay nice work";
else
report " not equal to 5 and 6";
end loop;
wait;
end process;
end architecture;
In VHDL, the keywords are if, elsif and else
if condition_1 then
-- do something
elsif condition_2 then
-- do something else
else
-- do something when all other conditions are false
end if;
Related
I wrote a code to make a 3-1 multiplexer with 1 selector which works by selector pulses,and Here's the code i wrote below.
However, the the output assigns to the input and its chance ONLY During the if condition. How to make it always assigns to that value whenever it changes ?
library ieee;
use ieee.std_logic_1164.all;
entity selector is
port( ip,selec: in std_logic;
a,b,c: inout std_logic);
end selector;
architecture Behaviour of selector is
signal temp : std_logic;
begin
process(selec)
begin
if (selec'EVENT and selec ='1') then
if(a = ip) then
temp<= b;
elsif (b = ip) then
temp <= c;
else
temp <= a;
end if;
end if;
end process;
end if;
end Behaviour;
I'm using only ModelSim since i don't have access to hardware to test on :(
In your process you have only included selec in the sensitivity list. Therefore the assignment to temp only takes place upon event on selec.
This would be much better suited to a conditional assignment.
https://www.ics.uci.edu/~jmoorkan/vhdlref/cond_s_a.html
signal_name <= expression_1 when condition_1 else
expression_2 when condition_2 else
expression_3 ;
case (my_state_val & val_q) is
when ("000" & "00") => do something;
when ("001" & "00") => do something else;
when ("010" & "10") => do a 3rd thing;
when ("100" & "DONT CARE") => do a non-default thing because my_state_val is valid;
when others => default state or null;
end case;
If it was an if check, I could do: val_q /= "11" because I know my counter will never reach the top value. How can I do this in a case statement?
The reason why I want a case statement is because I don't want a 30+ depth branches.
if 1 then
elsif 2 then
...
elsif 25 then
elsif 26 then
elsif 27 then
else
end if;
I would suggest either this:
case (my_state_val & val_q) is
when ("000" & "00") => do something;
when ("001" & "00") => do something else;
when ("010" & "10") => do a 3rd thing;
when others =>
if my_state_val == "100" then
do a non-default thing because my_state_val is valid
else
default state or null;
end if;
end case;
Or this:
case (my_state_val) is
when ("000") => Evaluate val_q;
when ("001") => Evaluate val_q;
when ("010") => Evaluate val_q;
when ("100") => Evaluate val_q;
when others => default state or null;
end case;
I initially attempted this:
case (my_state_val & val_q) is
when ... => ....;
...
when ("100" & "--") => do something;
when others => null;
end case;
Simulation worked. However, my mentors are used to non-2008 VHDL and even if it was synthesize-able, it could raise questions by other engineers. So I want something that passes our coding guidelines.
I used an if-else wrapped around this case statement.
if my_state_val = "100" then
my do something here;
else
case (my_state_val & val_q) is
when ... => ....;
...
-- removed "--"
when others => null;
end case;
end if;
I'm trying to write a code for multiplying two 100x100 matrices in vhdl
library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use ieee.numeric_std.all;
library work;
use work.mult_100x100_pack.all;
entity multiplier_main_code is
Port ( in_matrix1 : in t_2d_array;
in_matrix2 : in t_2d_array;
out_matrix : inout t_2d_array);
end multiplier_main_code;
architecture Behavioral of multiplier_main_code is
begin
process(in_matrix1, in_matrix2)
begin
for i in 0 to 99 loop
for j in 0 to 99 loop
for k in 0 to 99 loop
out_matrix(i)(j) <= std_logic_vector(signed(out_matrix(i)(j)) + (signed(in_matrix1(i)(k)) * signed(in_matrix2(k)(j))));
end loop;
end loop;
end loop;
end Behavioral;
Its again and again showing an error saying:
expecting type void for "behavioral"
syntax error near "Behavioral"
The code for mult_100X100_pack package is:
library IEEE;
use IEEE.STD_LOGIC_1164.all;
use ieee.numeric_std.all;
package mult_100x100_pack is
type t_1d_array is array(integer range 0 to 99)of std_logic_vector(7 downto 0);
type t_2d_array is array(integer range 0 to 99)of t_1d_array;
end mult_100x100_pack;
Please, can anybody help me to get around this error?
After fixing your indentation, it should be quite obvious what you are missing:
process(in_matrix1, in_matrix2)
begin
for i in 0 to 99 loop
for j in 0 to 99 loop
for k in 0 to 99 loop
-- Do things
end loop;
end loop;
end loop;
-- Perhaps `end process;` might be appropriate here...
Your process needs an end process; :
end loop;
end process;
end Behavioral;
This illustrates the advantage of taking care to indent code correctly. If all your end fors lined up with their corresponding fors, this would have been obvious.
I am trying to make a fsm in vhdl using modelsim but when i try and compile my code i have this errors
** Error: C:/Users/manor/Desktop/ldh/mult_fsm.vhd(34): near "when": (vcom-1576) expecting END.
** Error: C:/Users/manor/Desktop/ldh/mult_fsm.vhd(60): near "when": (vcom-1576) expecting END.
** Error: C:/Users/manor/Desktop/ldh/mult_fsm.vhd(72): near "else": (vcom-1576) expecting END.
And this is my code
library ieee;
use ieee.std_logic_1164.all;
entity mult_fsm is
port(ck,adx,m: in std_logic;
adsh,sh,cm,mdone: out std_logic);
end entity mult_fsm;
architecture ideal of mult_fsm is
type StateType is (S0, S1, S2, S3, S4);
signal CurrentState, NextState: StateType;
begin
NS_CS: process( ck)
begin
if ck'event and ck='1' then
case CurrentState is
when S0=>
if (adx='0') then
NextState <= S0;
else
NextState <= S1;
end if;
when S1=>
NextState <= S2;
when S2=>
if (m='1') then
NextState<=S3;
else if (m='0') then
NextState<=S2;
end if;
when S3=>
NextState <= S4;
when S4=>
NextState <= S0;
end case;
end if;
end process NS_CS;
OL: process (CurrentState)
begin
case CurrentState is
when S0=>
if (adx = '0') then
adsh<='0';
sh<='0';
cm<='0';
mdone<='0';
else if (adx = '1') then
if (m='1') then
adsh<='1';
else if (m='0') then
sh<='1';
end if;
end if;
when S1=>
if (m='1') then
adsh<='1';
else if (m='0') then
sh<='1';
end if;
when S2=>
if (m='0') then
adsh<='0';
sh<='0';
cm<='0';
mdone<='0';
else if (m='1') then
adsh<='1';
end if;
when S3=>
if (m='0') then
sh='1';
else if (m='1') then
cm<='1';
adsh<='1';
end if;
when S4=>
mdone<='1';
end case;
end process OL;
end architecture ideal;
I tried fixing the code myself but i just can't figure out what is the problem with it.
Replace your else ifs with elsifs.
In VHDL, each if needs an end if. If you write
if ... then
...
else if ... then
you need two end ifs - one for each if:
if ... then
...
else IF ... THEN
...
END IF;
end if;
VHDL has an elsif statement. That does not start a new if statement, but instead is part of the if statement it follows. If you replace else IF in the above example, you only need one end if:
if ... then
...
elsif ... then
...
end if;
Looking at the following code:
if (m='1') then
NextState<=S3;
else if (m='0') then
NextState<=S2;
end if;
I think you meant elsif instead of else if. Alternatively, since m is an std_logic, you may be able to simplify this block down to:
if (m='1') then
NextState<=S3;
else
NextState<=S2;
end if;
I have expression. How I can open or rewrite this?
if not ((A or B) and PAR like '%3%') then
--do some code
end if;
Can do this more simple?
Please, give me a link for another expressions as example.
The following should be close to what you're looking for:
IF A = FALSE AND B = FALSE AND REGEXP_LIKE(PAR, '[^3]') THEN
-- code here
END IF;
Share and enjoy.
try the following code
if(A!=true or B!=true)
if(REGEXP_LIKE(name,'[^r]'))
/*code has to be written here*/
end if;
end if;