別名（Alias）
別名的功能是代碼中已命名項的替換名。 An alternate name for an existing named item in the code.
語法（Syntax）
alias 別名 [ : 數據類型 ] is name [識別標志];識別標志= [類型名, ... ] return 類型名alias alias_name [ : data_type ] is name [ signature ]; signature = [ type_name, ... ] return type_name說明（Description）
別名可以是任何已存在目標的別稱：信號、變量、常量或文件。它也可以被用在“非目標”上，只要是提前定義的虛擬的一切，除了標簽，loop參數和generate參數。 The alias declares an alternative name for any existing object: signal, variable, constant or file. It can also be used for “non-objects”: virtually everything, which was PReviously declared, except for labels, loop parameters, and generate parameters.
如果別名代表一個子程序（包括一個運算符）或枚舉文字，則需要一個識別標簽（用來匹配參數和結果類型）。 If an alias denotes a subprogram (including an Operator) or enumeration literal then a signature (matching the parameter and result type) is required.
例程（Example）
signal Instruction: std_logic_vector(15 downto 0);alias OpCode : std_logic_vector(3 downto 0) is Instruction(15 downto 12); alias SrcAddr : std_logic_vector(1 downto 0) is Instruction(11 downto 10); alias DestAddr : std_logic_vector(1 downto 0) is Instruction(9 downto 8); alias InstData : std_logic_vector(7 downto 0) is Instruction(7 downto 0);注釋（Note）
許多綜合工具不支持別名。Many synthesis tools do not support aliases.新聞熱點
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