Adding Hex numbers

[Altera_Forum]

Hi, 

Does anyone know how can I add Hex numbers inside the process (VHDL)?  For instance, I want to add x"55" + x"55" but if I'll write " x"55" or x"55" " the answer will be x"55" (the answer should be x"AA"). Idan

[Altera_Forum]

--- Quote Start ---  Hi, Does anyone know how can I add Hex numbers inside the process (VHDL)?  For instance, I want to add x"55" + x"55" but if I'll write " x"55" or x"55" " the answer will be x"55" (the answer should be x"AA"). Idan  --- Quote End ---    Of course x"55" or x"55" is x"55" as this is a binary or, used on the vector bitwise.  Addition in VHDL (one of the reasons I prefer Verilog over HDL) requires type conversions as it has quite a strict type checking: result <= std_logic_vector(unsigned(x"55") + unsigned(x"55"));  Also please note that unless you do know exactly what you do an addition of two vectors with N and M bits require the result to be max(N,M) + 1 bit wide.

[Altera_Forum]

Thanks a lot...

[Altera_Forum]

I want to add two hex numbers inside the process… 

This is my code:   "  LIBRARY IEEE; USE IEEE.STD_LOGIC_1164.ALL; --USE IEEE.STD_LOGIC_ARITH.ALL; USE IEEE.STD_LOGIC_UNSIGNED.ALL; USE IEEE.NUMERIC_STD.ALL; --I using "conv_std_logic_vector" function … signal TX_checkSum: std_logic_vector (8 downto 0); begin process (clk) begin if reset='1' then … elsif clk'event and clk='1' then  TX_checkSum <= std_logic_vector(unsigned(x"55") + unsigned(x"55")); end if; end process; "   I get the following error:" Error (10408): VHDL error at UART.vhd(139): can't determine type of object at or near string ""01010101"" -- found 25 possible types". What could be the problem?