CL-PS7500FE View Datasheet(PDF) - Cirrus Logic

Part Name

Description

Manufacturer

CL-PS7500FE

System-on-a Chip for Internet Appliance

Cirrus Logic 

CL-PS7500FE

System-on-a-Chip for Internet Appliance

6.3.3 Level One Descriptor

The Level One descriptor returned is either a Page Table descriptor or a Section descriptor, and the format

varies accordingly. Figure 6-4 illustrates the format of Level One descriptors.

31

20 19

PAGE TABLE BASE ADDRESS

SECTION BASE ADDRESS

12 11 10 9 8

54321 0

0 0 FAULT

DOMAIN 1

0 1 PAGE

AP

DOMAIN 1 C B 1 0 SECTION

1 1 RESERVED

Figure 6-4. Level One Descriptors

The two least-significant bits indicate the descriptor type and validity, and are interpreted as in Table 6-1.

Table 6-1. Interpreting Level One Descriptor Bits 1:0

Value

00

01

10

11

Meaning

Invalid

Page

Section

Reserved

Notes

Generates a Section Translation fault.

Indicates that this is a Page descriptor.

Indicates that this is a Section descriptor.

Reserved for future use.

6.3.4 Page Table Descriptor

Bit Description

3:2 Always write as ‘0’.

4 Write as ‘1’ for backward compatibility.

8:5 Specify one of the sixteen possible domains (held in the Domain Access Control register) that contain the primary

access controls.

31:10 Form the base for referencing the Page Table entry. (The page table index for the entry is derived from the virtual

address as illustrated in Figure 6-7 on page 45.)

If a Page Table descriptor is returned from the Level One fetch, a Level Two fetch is initiated, as described

in the following section.

June 1997

ADVANCE DATA BOOK v2.0

41

ARM PROCESSOR MMU

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