Case Statement Example:Function of Arithmetic Mod.

architecture arithmetic_module_arch of arithmetic_module is

-- multiplication returns a result with length = sum of lengths of operands

signal ext_result : std_logic_vector(OPERAND_WIDTH*2-1 downto 0);

begin

EVAL_ARITH: process(operandA, operandB, operation)

begin

case operation is

when ADD =>

ext_result(OPERAND_WIDTH-1 downto 0) <= operand1 + operand2;

when SUB =>

ext_result(OPERAND_WIDTH-1 downto 0) <= operand1 - operand2;

when MUL =>

ext_result <= operand1 * operand2;

when NEG =>

ext_result(OPERAND_WIDTH-1 downto 0) <= ZERO - operand1;

-- cover all cases not explicitly stated in case statement

when others =>

ext_result <= (others => '0');

end case;

end process EVAL_ARITH;

end arithmetic_module_arch;

Case Statement Example: Function of Arithmetic Mod.