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Basic VHDL quiz – Part 2
Test your coding skills with this VHDL quiz after completing tutorials 6-11 from the Basic VHDL Tutorial series!
How to create a signal vector in VHDL: std_logic_vector
The std_logic_vector type can be used for creating signal buses in VHDL. The std_logic is the most commonly used type in VHDL, and the std_logic_vector is the array version of it. While the std_logic is great for modeling the value that can be carried by a single wire, it’s not very practical for implementing collections…
std_logic vs std_ulogic
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How to use a For loop in VHDL
In the previous tutorial we learned to create an infinite loop by using the loop statement. We also learned how the break out of a loop by using the exit statement. But what if we want the loop to iterate a certain number of times? The For-Loop is the easiest way to accomplish this. The…
How to use Signed and Unsigned in VHDL
The signed and unsigned types in VHDL are bit vectors, just like the std_logic_vector type. The difference is that while the std_logic_vector is great for implementing data buses, it’s useless for performing arithmetic operations. If you try to add any number to a std_logic_vector type, ModelSim will produce the compilation error: No feasible entries for…
How to use a Case-When statement in VHDL
The Case-When statement will cause the program to take one out of multiple different paths, depending on the value of a signal, variable, or expression. It’s a more elegant alternative to an If-Then-Elsif-Else statement with multiple Elsif’s. Other programming languages have similar constructs, using keywords such as a switch, case, or select. Among other things,…
First of all, thank you so very much!
These are by far the most comprehensible tutorials I have come across like ever!
Brilliant work.
So here my two cents out of gratitude:
Basic VHDL Quiz – part 4
Which statement is not true?
Answer 3 : The return statement cannot be omitted.
-> Correct
So the return statement CAN be omitted???
“Unlike in most other programming languages, the return keyword is mandatory in functions in VHDL.”
Confused by double negation. Me or you 😉
Good catch! I’ve changed the answer now. I was trying to make you think, but in the process I confused myself too 🙂
“The return-keyword cannot be used in a procedure”. I believe that this is incorrect, e.g.
https://web.archive.org/web/20200629023040/http://vhdl.renerta.com:80/source/vhd00060.htm
It is true, of course, that you cannot return a value with it, that’s the only (?) difference between procedures and functions. But, as in other languages, you can use “return” as control flow statement to “force an exit”.
You are right! I missed the possibility of using return statements in procedures without returning a value. According to the Renata link you posted, functions must return a value, while procedures can have return statements, but then without a return value.
I am changing this question.