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关于DC中的target_library和link_library的区别

2014-08-03 22:13阅读：

http://blog.sina.cn/dpool/blog/u/3453506970

首先说的是，Synopsys规定，logic library 必须是db格式。包含target_library和link_library


关于target_library，DC规范中明确定义：
Design Compiler selects functionally correct gates from the target libraries to build a circuit during mapping. It also calculates the timing of the circuit by using the vendor-supplied timing data for these gates.
To specify the target libraries, use the target_library variable. Your should specify only the standard cell libraries that you want Design Compiler to use for mapping the standard cells in your design, such as combinational logic and registers. You should not specify any DesignWare libraries or macro libraries, such as pads or memories.
意思也就是说，target_library是DC在综合做mapping的时候，到这个目录下寻找使用到的标准单元库
关于link_library，一个完整的design的所有单元的的实例化，都必须要能够与相关library和引用的其他design连接起来。这个过程叫做linking the design or resolving references. To resolve references, Design Compiler uses the link libraries set by the foll
owing variables and attribute:
  • The link_library application variable lists the libraries and design files that Design Compiler uses to resolve references.
  • Design Compiler searches the files listed in the link_library variable from left to right, and it stops searching when it finds a reference. Specifying an asterisk in the link_library variable means that Design Compiler searches loaded libraries in memory for the reference. For example, if you set the link_library variable to {'*' lsi_10k.db}, Design Compiler searches for the reference in memory first and then in the lsi_10k library.
  • The local_link_library attribute lists the design files and libraries added to the beginning of the link_library variable during the link process. Design Compiler searches files in the local_link_library attribute first when it resolves references. You can set this attribute by using the set_local_link_library command.
  • The search_path variable specifies a list of directory paths that the tool uses to find logic libraries and other files when you specify a plain file name without a path. It also sets the paths where Design Compiler can continue the search for unresolved references after it searches the link libraries.

如果在link_library中没有找到相关单元的引用，DC会去search_pathd定义的目录中去搜索。link库包含你的设计中所有reference到的cell ，std cell ，general tech ,IO, IP


link_library是查找reference需要的，主要进行mapping target_library主要是用于优化、综合。例如读入一个网表，网表中的cell必须能在link_library里面进行mapping，然后执行compile命令时使用target_library进行优化.
Symbol library包含了所有library cells的图形符号表示，DC使用symbol library来产生schematic view。library cell与symbol的关系是一对一的。
To set up access to the logic libraries, you must specify the target libraries and link libraries.
DesignWare library是支持设计重用的一些电路设计的模块
DC在topographical模式下，除了logic library外，还要physical library。You use the Milkyway design library to specify physical libraries and save designs in Milkyway format.
相关输入文件：Milkyway reference library和Milkyway technology file （.tf）
关于DC中的target_library和link_library的区别

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