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;

5

2 Answers

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;

1

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;

Your Answer

Sign up or log in

Sign up using Google Sign up using Facebook Sign up using Email and Password Submit

Post as a guest

Post Your Answer Discard

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.