HDL之Bitwise operation

1　　Verilog

1.1　　Bitwise operator

　　Bitwise operators perform a bit wise operation on two operands.

　　They take each bit in one operand and perform the operation with the corresponding bit in the other operand.

　　If one operand is shorter than the other, it will be extended on the left side with zeroes to match the length of the longer operand.

1.2　　Reduction operator

　　Reduction operators are unary.

　　They perform a bit-wise operation on a single operand to produce a single bit result.

　　Reduction unary NAND and NOR operators operate as AND and OR respectively, but with their outputs negated.

2　　VHDL

　　FUNCTION and_reduce (arg : STD_LOGIC_VECTOR) RETURN STD_LOGIC;

　　 -- Result subtype: STD_LOGIC.

　　 -- Result: Result of and'ing all of the bits of the vector.

　　　　function nand_reduce (arg : std_logic_vector )

　　　　　　return std_logic is

　　　　begin

　　　　　　return not and_reduce (arg);

　　　　end;

　　 Others are nand_reduce, or_reduce, nor_reduce, xor_reduce, xnor_reduce

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