VHDL code for simple calculation: b = 68 - (a/25)

I recommend to use package numeric_std from the IEEE library to ease the description of arithmetic calculations. In order to do, use the following clauses:

library ieee;

use ieee.std_logic_1164.all;

use ieee.numeric_std.all;

The source code then becomes:

signal a: unsigned(10 downto 0);

signal b: unsigned(10 downto 0);

process(a)

variable tmp1: unsigned(10 downto 0);

variable tmp2: unsigned(10 downto 0);

begin

tmp1 := a / 25;

tmp2 := 68 - tmp1;

b <= tmp2;

end process;

One last point: the results of 68-tmp1 may be negative (for example when a=2047). This may be a problem since tmp2 is declared as an unsigned...

--jmv