SPRUI30H November 2015 – May 2024 DRA745 , DRA746 , DRA750 , DRA756
The first-level translation table describes the translation properties for 1-MiB sections. To describe a 4-GiB address range requires 4096 32-bit entries (so-called first-level descriptors).
The first-level translation table start address must be aligned on a multiple of the table size with a 128-byte minimum. Consequently, an alignment of at least 16K bytes is required for a complete 4096-entry table; that is, at least the last fourteen address bits must be zero.
The start address of the first-level translation table is specified by the so-called translation table base. The table is indexed by the upper 12-bits of the virtual address. Figure 20-8 shows this mechanism.
To summarize, the translation table base and the translation table index together define the first-level descriptor address. Figure 20-9 outlines the precise mechanism used to calculate this address.
As an example of this mechanism, consider a translation table base address of 0x8000:0000 and a virtual address of 0x1234:5678. In this case, the first-level descriptor address is 0x8000:0000 + (0x123 << 2) = 0x8000:048C.