First-level descriptor bit assignments: Priority encoding of fault status

 

 

 

WO R K I N G W I T H T H E C P U

. .

 

 

 

 

 

 

 

MemoryManagement Unit (MMU)..

 

 

 

 

.

 

 

 

 

 

Bits

 

 

 

 

Section

Coarse

Fine

Description

 

 

 

 

 

 

[31:20]

[31:10]

[31:12]

Forms the corresponding bits of the physical address.

 

 

 

 

 

 

[19:12]

----

---

SHOULD BE ZERO

 

 

 

 

 

 

[11:10]

---

---

Access permission bits. See “Access permissions and

 

 

 

 

domains” on page 106 and “Fault Address and Fault Status

 

 

 

 

registers” on page 119 for information about interpreting

 

 

 

 

the access permission bits.

 

 

 

 

 

 

9

9

[11:9]

SHOULD BE ZERO

 

 

 

 

 

 

[8:5]

[8:5]

[8:5]

Domain control bits

 

 

 

 

 

 

4

4

4

Must be 1.

 

 

 

 

 

 

[3:2]

---

---

Bits C and B indicate whether the area of memory mapped

 

 

 

 

by this page is treated as write-back cachable, write-

 

 

 

 

through cachable, noncached buffered, or noncached

 

 

 

 

nonbuffered.

 

 

 

 

 

 

---

[3:2]

[3:2]

SHOULD BE ZERO

 

 

 

 

 

 

[1:0]

[1:0]

[1:0]

These bits indicate the page size and validity, and are

 

 

 

 

interpreted as shown in “First-level descriptor bit

 

 

 

 

assignments: Priority encoding of fault status” on

 

 

 

 

page 111.

 

 

 

 

 

 

First-level descriptor bit assignments: Interpreting first level descriptor bits [1:0]

Value

Meaning

Description

 

 

 

0 0

Invalid

Generates a section translation fault.

 

 

 

0 1

Coarse page table

Indicates that this is a coarse page table descriptor.

 

 

 

1 0

Section

Indicates that this is a section descriptor.

 

 

 

1 1

Fine page table

Indicates that this is a fine page table descriptor.

 

 

 

Section descriptor A section descriptor provides the base address of a 1 MB block of memory.

Section descriptor

format

31

20

19

12

11

10

9

8

5

4

3

2

1

0

 

Section base address

 

SBZ

 

AP

S

Domain

 

1

C

B

1

0

 

 

 

B

 

 

 

 

 

 

 

 

Z

 

 

 

 

 

 

 

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Digi NS9215 manual Section descriptor Format, Bits Section Coarse Fine Description, Value Meaning Description

NS9215 specifications

The Digi NS9215 is a powerful solution designed for industrial applications that require reliable connectivity and robust performance. Built on a foundation of advanced technologies, the NS9215 serves as a versatile networking device that meets the demands of automation, remote monitoring, and data acquisition.

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