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Cache after implemtenig BOOT ROM

The BOOT ROM mounted in the 32X, both master and slave, purges (initializes) and

enables the cache immediately after SLEEP from the initial program of the MEGA Drive

side has been canceled. At this time, 4-way mode, data replace, and command replace can

be selected. Initial data is loaded and settings stay unchanged until the application is

implemented.

Applications can be executed without tinkering with theses settings, but when transferring

DMA in the address are where cache is used, the operation can result in differences in the

cache memory and external memory contents, and therefore, purge becomes necessary.

Purge of all entries, and the purge of a specific line should be differentiated in response to

the need.

Purge (Cache Initialization)

Purge of all entries

If "1" is written to the CP bit of the cache control register (CCR), all cache entries will be

purged.

Purge of specific line

In associative purge spaces (4000 0000h ~5FFF FFFFh), the cache address to purge is

offset, and if write accessed, is checked 4 ways at the same time and only lines that

include correpsonding addresses are purged. For example, when the slave side cache is

purged because contents of the master side 0600 1004h address are replaced, write access

is performed in the 4600 1004h address by the slave CPU.

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Sega 32X Handbuch Seite 66