请帮我看看这个程序怎么REJECT 语句发生编译错误啊 REJECT, 语句, 程序, 编译

新820665

请帮我看看这个程序怎么REJECT 语句发生编译错误啊 错误是：identifier "REJECT" has not been declared; 怎么去声名?谢谢! LIBRARY IEEE; USE IEEE.STD_LOGIC_1164.ALL; USE IEEE.STD_LOGIC_ARITH; ENTITY dff_first IS PORT ( clk : IN STD_LOGIC; q : OUT STD_LOGIC); END dff_first; ARCHITECTURE dff1 OF dff_first IS BEGIN PROCESS (clk) VARIABLE tmp:STD_LOGIC:='0'; BEGIN IF clk='1' AND clk'EVENT THEN --AND clk'LAST_VALUE = '0' THEN q<=NOT tmp ; tmp:=NOT tmp; END IF; END PROCESS; END dff1; ----------------------- ENTITY muxdff IS PORT (clk : IN STD_LOGIC; cp : OUT STD_LOGIC); END muxdff; ARCHITECTURE mux_dff1 OF muxdff IS COMPONENT dff_first PORT(clk : IN STD_LOGIC; q : OUT STD_LOGIC); END COMPONENT; SIGNAL u: STD_LOGIC_VECTOR(0 TO 2); SIGNAL sig_det : STD_LOGIC; BEGIN dff_1: dff_first PORT MAP (clk,u(0)); g1: FOR i IN 1 TO 2 GENERATE dff_1:dff_first PORT MAP (u(i-1),u(i)); END GENERATE; sig_det <= clk AND u(0) AND u(1) AND u(2); cp <= REJECT 20 ns INERTAL sig_det AFTER 2 ns; END mux_dff1;