3.3.4. Section descriptor

A section descriptor provides the base address of a 1MB block of memory. Figure 3.5 shows the format of a section descriptor.

Figure 3.5. Section descriptor

Section descriptor bit assignments are described in Table 3.4.

Table 3.4. Section descriptor bits

Bits

Description

31:20

Form the corresponding bits of the physical address for a section

19:12

Always written as 0

11:10

(AP) Specify the access permissions for this section

9

Always written as 0

8:5

Specify one of the 16 possible domains (held in the domain access control register) that contain the primary access controls

4

Should be written as 1, for backward compatibility

3:2

These bits (C and B) indicate whether the area of memory mapped by this section is treated as write-back cachable, write-through cachable, noncached buffered or noncached nonbuffered

1:0

These bits must be 10 to indicate a section descriptor

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