求助

[qq_44423882]

这个vhdl语句能不能帮我详解一下，多谢       LIBRARY ieee;       USE ieee.std_logic_1164.all;       ENTITY shift IS       PORT(a,cIk:IN STD＿LOGIC;       b :OUT STD＿LOGIC); END;       ARCHITECTURE gen_ shift OF shift IS       COMPONENT my- dff IS        PORT(d,clk:IN STD_LOGIC;                q        : OuT STD_L0GIC; END COMPONENT ;       SIGNAL z:STD_ LOGIC_VECTOR(O TO 4); BEGIN       z(0)＜= a;       g1:FOR i IN O TO 3 GENERATE        u1: my_dff PORT MAP( z(i). clk, z(i+1)); ENO GENERATE;       b<=z(4);  END: