A PROGRAMMABLE SRAM AND DRAM CACHE INTERFACE

摘要

A cache interface that supports both Static Random Access Memory (SRAM) and Dynamic Random Access Memory (DRAM) is disclosed. The cache interface preferably comprises two portions, one portion (133) on the processor (130) and one portion (180) on the cache (110). A designer can simply select which RAM he or she wishes to use for a cache, and the cache controller interface portion (133) on the processor (130) configures the processor (130) to use this type of RAM. The cache interface portion (180) on the cache (110) is simple when being used with DRAM in that a busy indication is asserted so that the processor (130) knows when an access collision occurs between an access generated by the processor (130) and the DRAM cache. An access collision occurs when the DRAM cache is unable to read or write data due to a precharge, initialization, refresh, or standby state. When the cache interface is used with an SRAM cache, the busy indication is preferably ignored by a processor and the processor's (130) cache interface portion (133). Additionally, the disclosed cache interface allows speed and size requirements for the cache to be programmed into the interface. In this manner, the interface does not have to be redesigned for use with different sizes or speeds of caches.