zoukankan      html  css  js  c++  java
  • VHDL之concurrent之generate

    GENERATE

      It is another concurrent statement (along with operators and WHEN). It is equivalent to the sequential statement LOOP in the sense that it

    allows a section of code to be repeated a number of times, thus creating several instances of the same assignments. 

      1)  FOR / GENERATE: notice that GENERATE must be labeled.

    label: FOR identifier IN range GENERATE
      (concurrent assignments)
    END GENERATE;

      2)  IF/GENERATE

       An irregular form is also available, which uses IF/GENERATE (with an IF equivalent; recall that originally IF is a sequential statement). Here ELSE is not allowed.  

    label1: FOR identifier IN range GENERATE
      ...
    label2: IF condition GENERATE
      (concurrent assignments)
    END GENERATE;
    ...
    END GENERATE;

    Example 1

    SIGNAL x: BIT_VECTOR (7 DOWNTO 0);
    SIGNAL y: BIT_VECTOR (15 DOWNTO 0);
    SIGNAL z: BIT_VECTOR (7 DOWNTO 0);
    ...
    G1: FOR i IN x'RANGE GENERATE
      z(i) <= x(i) AND y(i+8);
    END GENERATE;

    Example 2  Vector Shifter

      The output vector must be a shifted version of the input vector, with twice its width and an amount of shift specified by another input.

    For example, if the input bus has width 4, and the present value is ‘‘1111’’, then the output should be one of the lines of the following

    matrix (the original vector is underscored):

      row(0): 0 0 0 0 1 1 1 1

      row(1): 0 0 0 1 1 1 1 0

      row(2): 0 0 1 1 1 1 0 0

      row(3): 0 1 1 1 1 0 0 0

      row(4): 1 1 1 1 0 0 0 0

    1 ------------------------------------------------
    2 LIBRARY ieee;
    3 USE ieee.std_logic_1164.all;
    4 ------------------------------------------------
    5 ENTITY shifter IS
    6 PORT ( inp: IN STD_LOGIC_VECTOR (3 DOWNTO 0);
    7     sel: IN INTEGER RANGE 0 TO 4;
    8     outp: OUT STD_LOGIC_VECTOR (7 DOWNTO 0));
    9 END shifter;
    10 ------------------------------------------------
    11 ARCHITECTURE shifter OF shifter IS
    12   SUBTYPE vector IS STD_LOGIC_VECTOR (7 DOWNTO 0);
    13   TYPE matrix IS ARRAY (4 DOWNTO 0) OF vector;
    14   SIGNAL row: matrix;
    15 BEGIN
    16   row(0) <= "0000" & inp;
    17   G1: FOR i IN 1 TO 4 GENERATE
    18     row(i) <= row(i-1)(6 DOWNTO 0) & '0';
    19   END GENERATE;
    20   outp <= row(sel);
    21 END shifter;
    22 ------------------------------------------------
  • 相关阅读:
    java xpath
    structs2 Interceptor
    jetbrains idea web help
    Java xpath example code THE RIGHT WAY
    java xpath engine
    本地安装jruby到maven仓库,由于公司网络不给力
    skybe的linux下的版本下载
    mybastis学 rails有migration了
    Using Java from Ruby with JRuby IRB
    PropertyPlaceholderConfigurer
  • 原文地址:https://www.cnblogs.com/mengdie/p/4518568.html
Copyright © 2011-2022 走看看