How to use Signed and Unsigned in VHDL

Learn how to represent numbers in VHDL by using the Signed and Unsigned types. These can be used for representing integers and natural numbers of a custom bit range in VHDL.
The blog post for this video:
vhdlwhiz.com/s...
To use the Signed and Unsigned types, we have to import an IEEE library at the top of the .vhd file like this:
library ieee;
use ieee.numeric_std.all;
The syntax for declaring signals of Signed or Unsigned type is:
signal MySigned : signed(range) := initial_value;
signal MyUnsigned : unsigned(range) := initial_value;
The "range" and "initial_value" must of course be replaced with something else. A valid 8-bit range could for example be (7 downto 0).
When assigning initial values or when performing regular assignments, there are several ways to do this.
Of course you can assign from one signal to another:
MySigned1 ＜= MySigned2;
You can also assign a value using binary or hexadecimal notation:
MySigned1 ＜= "10101010";
MySigned2 ＜= x"AA";
If you want to assign an integer number directly, it won't work. You have to perform a conversion to either Signed or Unsigned:
MySigned ＜= to_signed(170, MySigned’length);
MyUnsigned ＜= to_unsigned(170, MyUnsigned’length);
Signed and Unsigned types are very much like the std_logic_vector type. The main difference is how they are treated by the compiler/synthesizer. While you can't add two std_logic_vectors, you can add or subtract two Signed or Unsigned signals by using the + or - operator.
The difference between SIgned and Unsigned signals are most apparent when they overflow or underflow. If a signed vector overflows it will suddenly have the most negative value that it can represent, while an Unsigned will go back to 0. Of course, only Signed types can represent negative numbers.
Take care, and choose your bit ranges wisely!

[@arsalansyed4709]

Thank you so much! You helped me a ton with my first internship

[@vergil1444]

Would u help me I'm wondering how to make a vhdl code for hex adder. I mean the module gets hex number from input porta and add them and puts the result in output port

[@mdrezaulkarim47]

during signed addition: we did 2's complement of Signcnt4 = '"1000=00001000= 11110111+1=11111000" value..then did addition with Sgncnt8="00000000"=1111 1000 = 8hF8

[@RatedA4Aliens]

And the reason it did 2's complement is cause the sign bit was set (bit 3), otherwise it would've just done a simple addition

[@marcinmrozek5079]

How did the odometer clock over in park mode?! :)

[@JisooMx]

with exercise I can make somenthig like this? signal res: unsigned(7 downto 0) := (others => '0'); res

[@JustDena00]

How can I change te numbers in the wave form from binary to hexadecimal? I have binary by default

[@VHDLwhiz]

Right-click the signal name in the waveform's sidebar. Select Radix->Hexadecimal

[@AhmadAsmndr]

Thanks a lot!