AMBA-AXI协议详解,FPGA设计必备

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Introduction to AMBA AXI4

Non-Confidential

Issue 0101

102202

Introduction to AMBA AXI4

102202

Issue

Non-Confidential

Page 2 of 60

Introduction to AMBA AXI4

Release information

Document history

Issue Date Confidentiality Change

01 25 August 2020 Non-Confidential First release

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Introduction

to AMBA AXI4

102202

Issue

Non-Confidential

Page 4 of 60

Contents

1 Overview ..................................................................................................................................................................... 6

2 What is AMBA, and why use it? ........................................................................................................................... 7

2.1 Where is AMBA used? ............................................................................................................................................................. 7

2.2 Why use AMBA? ......................................................................................................................................................................... 8

2.3 How has AMBA evolved?....................................................................................................................................................... 8

2.3.1 AMBA 1 ....................................................................................................................................................................................... 9

2.3.2 AMBA 2 ....................................................................................................................................................................................... 9

2.3.3 AMBA 3 ....................................................................................................................................................................................... 9

2.3.4 AMBA 4 .................................................................................................................................................................................... 10

2.3.5 AMBA 5 .................................................................................................................................................................................... 10

3 AXI protocol overview ........................................................................................................................................ 11

3.1 AXI in a multi-master system ............................................................................................................................................ 12

3.2 AXI channels .............................................................................................................................................................................. 14

3.3 Main AXI features ................................................................................................................................................................... 15

4 Channel transfers and transactions ................................................................................................................ 17

4.1 Channel handshake ................................................................................................................................................................ 17

4.2 Differences between transfers and transactions .................................................................................................. 17

4.3 Channel transfer examples ................................................................................................................................................ 19

4.4 Write transaction: single data item ............................................................................................................................... 21

4.5 Write transaction: multiple data items ....................................................................................................................... 23

4.6 Read transaction: single data item ................................................................................................................................ 24

4.7 Read transaction: multiple data items ......................................................................................................................... 26

4.8 Active transactions ................................................................................................................................................................ 27

5 Channel signals....................................................................................................................................................... 29

5.1 Write channel signals ............................................................................................................................................................ 29

5.2 Read channel signals ............................................................................................................................................................. 30

5.3 Data size, length, and burst type .................................................................................................................................... 32

5.4 Protection level support ..................................................................................................................................................... 32

5.5 Cache support ........................................................................................................................................................................... 33

Introduction to AMBA AXI4

102202

Issue

Non-Confidential

Page 5 of 60

5.6 Response signaling ................................................................................................................................................................. 35

5.7 Write data strobes ................................................................................................................................................................. 35

5.8 Atomic accesses with the lock signal ............................................................................................................................ 36

5.9 Quality of service .................................................................................................................................................................... 37

5.10 Region signaling .................................................................................................................................................................... 38

5.11 User signals .............................................................................................................................................................................. 38

5.12 AXI channel dependencies .............................................................................................................................................. 39

6 Atomic accesses ..................................................................................................................................................... 40

6.1 Locked accesses ....................................................................................................................................................................... 40

6.2 Exclusive accesses .................................................................................................................................................................. 42

6.3 Exclusive access hardware monitor operation ....................................................................................................... 42

6.4 Exclusive transaction pairs: both pass ......................................................................................................................... 43

6.5 Exclusive transaction pairs: one pass, one fail ........................................................................................................ 45

7 Transfer behavior and transaction ordering ................................................................................................ 47

7.1 Examples of simple transactions .................................................................................................................................... 47

7.2 Transfer IDs ............................................................................................................................................................................... 49

7.3 Write transaction ordering rules ................................................................................................................................... 50

7.4 Read transaction ordering rules ..................................................................................................................................... 51

7.5 Read and write channel ordering ................................................................................................................................... 53

7.6 Unaligned transfer start address ................................................................................................................................... 54

7.7 Endianness support ............................................................................................................................................................... 55

7.8 Read and write interface attributes ............................................................................................................................. 56

8 Check your knowledge ........................................................................................................................................ 58

9 Related information ............................................................................................................................................. 59

10 Next steps .............................................................................................................................................................. 60