Method and apparatus for reducing RAM size while maintaining fast data acess

一种用于减少所需的RAM数量同时保持快数据存取的方法与装置。数据记录常保存在非易失性存储器以便即使在电路断电时仍维持数据记录的内容。在本发明中，每个在数据记录的非易失性RAM集合中的每条记录输入到函数H(x)，后者输出一标签值。经计算的标签值存入RAM中预定的存储器单元。每个经计算的标签长度上短于存储在非易失性RAM中的记录。因此与将整个数据记录集合存储在RAM中所需要的RAM相比，对每条数据记录保存一个标签值需要较少的RAM。当需要对应y的数据记录项时，计算H(y)的值。然后该H(y)值与标签值表中所有值比较。如果找到匹配，从其在非易失性RAM中的位置检索对应的记录，并与y比较。如果该值不匹配，搜索标签值表寻找其他位置匹配H(y)。其结果是仅需要最小量的RAM，就能与非易失性RAM的内容进行非常快速的比较。 A method and apparatus for reducing the amount of RAM required while maintaining fast data access. Data records are often saved in nonvolatile memory in order to maintain the contents of the data records even when the circuit is powered down. In the present invention each record in the nonvolatile RAM collection of data records is input to a function H(x) that outputs a tag value. The calculated tag value is saved in predetermined memory locations in RAM. Each calculated tag is shorter in length than the record saved in nonvolatile RAM. Therefore less RAM is required to save one tag value for each data record than is required to save the entire collection of data records in RAM. The value of H(y) is calculated when a data record entry corresponding to y is desired. Then the value of H(y) is compared to all the values in the tag value table. If a match is found, the corresponding record from its location in non-volatile RAM is retrieved and compared to y. If the values do not match the tag value table is searched for another location matching H(y). The result is a very fast comparison with the contents of nonvolatile RAM requiring only a minimal amount of RAM.