Cache Operation; Searching The Cache - Hitachi SH7709S Hardware Manual

5.3

Cache Operation

5.3.1

Searching the Cache

If the cache is enabled, whenever instructions or data in memory are accessed the cache will be
searched to see if the desired instruction or data is in the cache. Figure 5.4 illustrates the method
by which the cache is searched. The cache is a physical cache and holds physical addresses in its
address section.
Entries are selected using bits 11–4 of the address (virtual) of the access to memory and the
address tag of that entry is read. In parallel to reading of the address tag, the virtual address is
translated to a physical address in the MMU. The physical address after translation and the
physical address read from the address section are compared. The address comparison uses all four
ways. When the comparison shows a match and the selected entry is valid (V = 1), a cache hit
occurs. When the comparison does not show a match or the selected entry is not valid (V = 0), a
cache miss occurs. Figure 5.4 shows a hit on way 1.
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