7: Memory Management Unit7-14 EPSON ARM720T CORE CPU MANUAL7.3.11 Translating tiny page referencesFigure 7-12 shows the complete translation sequence for a 1KB tiny page.Figure 7-12 Tiny page translation from a fine page tablePage translation involves one additional step beyond that of a section translation. The levelone descriptor is the fine page table descriptor and this is used to point to the level onedescriptor.Note: The domain specified in the level one description and access permissions specifiedin the level one description together determine whether the access has permissionsto proceed. See sectionDomain access control on page 7-17 for details.7.3.12 SubpagesYou can define access permissions for subpages of small and large pages. If, during a pagewalk, a small or large page has a non-identical subpage permission, only the subpage beingaccessed is written into the TLB. For example, a 16KB (large page) subpage entry is writteninto the TLB if the subpage permission differs, and a 64KB entry is put in the TLB if thesubpage permissions are identical.When you use subpage permissions, and the page entry then has to be invalidated, you mustinvalidate all four subpages separately.31 14 13 0Translation base31 14 13 2 1 00 0Table indexTranslation baseModified virtual addressTranslation table base31 20 19 0Table index Page indexLevel one descriptorPhysical address31 0Fine page table base address Domain 1 12 13458911Level 2table index10 931 0Page indexPage base addressLevel two descriptor31 0Fine page table base address L2 table index 02 131 0Page base address10ap 11C B123456910121112910
