seagate SCSI SAS Product Manual

Users Guide

Serial Attached SCSI (SAS) Interface Manual

Users Guide

Serial Attached SCSI (SAS) Interface Manual

Publication number: 100293071, Rev. B

May 2006

Seagate, Seagate Technology, and the Seagate logo are registered tradem arks of Seagate Technology LLC. SeaTools, SeaFAX, SeaFONE, SeaBOARD, and SeaTDD are either registered trademarks or trade marks of Seagate Technology LLC. Other product names are registered trademarks or trademarks of their owners.

Seagate reserves the ri ght to change, without notice , product offerings or specifica tions. No part of this

publication may be reproduced in any form without written permission of Seagate Technology LLC.

Revision status summary sheet

Revision Date Writers/Engineers Notes

Rev. A 11/11/04 J. Coomes Initial release. Rev. B 05/07/06 C. Chalupa, J. Coomes, G. Houlder All.

Contents

1.0 Interface requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.1 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.2 How to use this interface manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.2.1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

1.2.2 Ap p l i c a b l e sp e c i fications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

1.2.3 O th e r re ferences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3

1.3 General interface description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.3.1 Introduction to Serial Attached SCSI Interface (SAS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3

1.3.2 T h e S AS i n te rface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.3.3 Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5

1.3.4 Keywords . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16

1.4 Physical interface characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

1.5 Bit and byte ordering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

2.0 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

2.1 Architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

2.1.1 Ar chitecture o v e rview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19

2.1.2 Physical links and phys. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

2.1.3 Ports (narrow ports and wide ports) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20

2.1.4 SAS devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

2.1.5 Expander devices (edge expander devices and fanout expander devices) . . . . . . . . . . . . . . . . . . . . . 22

2.1.6 Service delivery subsystem. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23

2.1.7 Domains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23

2.1.8 Expander device topologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

2.1.8.1 Expander device topology overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

2.1.8.2 Edge expander device set . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24

2.1.8.3 Expander device topologies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25

2.1.9 Pathways. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26

2.1.10 Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27

2.2 Names and identifiers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

2.2.1 Names and identifiers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

2.2.2 SAS addresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

2.2.3 Hashed SAS address . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31

2.2.4 D e vi c e n a mes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

2.2.5 Port identifiers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

2.2.6 Phy identifiers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

2.3 Resets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

2.3.1 R e se t overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

2.3.2 Hard reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

2.4 I_T nexus loss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

3.0 Phy layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

3.1 Phy layer overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

3.2 Encoding (8b10b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

3.2.1 En coding ove rv i e w . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

3.2.2 8b10b coding introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36

3.3 Encoding and decoding. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

3.4 Out of band (OOB) signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

3.5 Phy reset sequences. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

3.5.1 Phy reset sequences overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4 2

3.5.2 SAS to SAS phy reset sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

3.5.3 Phy reset sequence after devices are attached . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .47

3.5.2.1 SAS OOB sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42

3.5.2.2 SAS speed negotiation sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .44

3.6 DWS (dword synchronization). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

3.6.1 Acquiring DW S . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .49

3.6.2 L o si n g D WS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

3.7 Spin-up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

Serial Attached SCSI (SAS) Interface Manual, Rev. B i

4.0 Link layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

4.1 Link layer overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

4.2 Primitives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

4.2.1 Pr i mitives over v i e w . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

4.2.2 Primitive summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51

4.2.3 Primitive encodings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .55

4.2.4 Primitive sequences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .57

4.2.5 Primitives not specific to type of connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .60

4.2.6 Pr i mitives used only inside S SP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

4.2.4.1 Primitive sequences overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .57

4.2.4.2 Single primit ive sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

4.2.4.3 Triple primitive sequence. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .57

4.2.4.4 Redundant primitive sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .58

4.2.5.1 AIP (Arbitration in progress). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .60

4.2.5.2 ALIGN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

4.2.5.3 BREAK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

4.2.5.4 BROADCAST. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

4.2.5.5 CL O SE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

4.2.5.6 EOAF (End of address frame) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

4.2.5.7 ERR OR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .63

4.2.5.8 HARD_RESET. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .63

4.2.5.9 NO TIFY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

4.2.5.10 OPEN_ACCEPT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .64

4.2.5.11 OPEN_REJECT. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .64

4.2.5.12 SOAF (Start of address frame) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

4.2.6.1 ACK (Acknowledge). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .67

4.2.6.2 CREDIT_BLOCKED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .67

4.2.6.3 DO N E. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

4.2.6.4 EOF (End of frame) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .67

4.2.6.5 NAK (Negative acknowledgement) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .67

4.2.6.6 RRDY (Receiver ready). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .68

4.2.6.7 SOF (Start of frame) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .68

4.3 Clock skew management. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .69

4.4 Idle physical links. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70

4.5 CRC. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70

4.5.1 CRC overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .70

4.5.1.1 CRC field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .70

4.6 Scrambling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70

4.7 Address frames . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

4.7.1 Ad d ress frames o v e rview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

4.7.2 IDENTIFY address frame . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .72

4.7.3 OPEN address frame . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .74

4.8 Identification and hard reset sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .76

4.8.1 Identification and hard reset sequence overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .76

4.8.2 SAS initiato r device rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

4.8.3 Fanout expander device rules. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .77

4.8.4 Edge expander device rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .77

4.9 SAS domain changes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .78

4.9.1 Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78

4.9.1.1 Connections overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .78

4.9.1.2 Opening a connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .78

4.9.1.2.1 Connection request.................................................................. ....... .. .. .... .78

4.9.1.2.2 Connection responses .............................................................................79

4.9.1.3 Arbitration fairness. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .80

4.9.1.4 Arbitration and resource management in an expander device . . . . . . . . . . . . . . . . . . . . .81

4.9.1.4.1 Arbitration overview.................................................................................81

4.9.1.4.2 Arbitration status ......................................................................................82

4.9.1.4.3 Partial Pathway Timeout timer.......................................................... .. .... .82

4.9.1.4.4 Pathway recovery ....................................................................................82

4.9.1.5 Expander devices and connection requests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .83

4.9.1.5.1 All expander devices......................................................................... .... .. .83

4.9.1.5.2 Edge expander devices ...........................................................................83

4.9.1.5.3 Fanout expander devices.........................................................................83

4.9.1.6 Aborting a connection request . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84

ii Serial Attached SCSI (SAS) Interface Manual, Rev. B

4.9.1.7 Closing a connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85

4.9.2 R a te matching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87

4.9.3 SSP link layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

4.9.1.8 Breaking a connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

4.9.3.1 Opening an SSP connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

4.9.3.2 Full duplex . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .88

4.9.3.3 SSP frame transmission and reception . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .88

4.9.3.4 SSP flow control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .89

4.9.3.5 Interloc ked frames. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89

4.9.3.6 Closing an SSP connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91

5.0 Transport layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

5.1 Transport layer overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

5.2 SSP transport layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

5.2.1 SSP frame format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

5.2.2 In f o r mation units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96

5.2.2.1 COMMAND information unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .96

5.2.2.2 TASK informat io n unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97

5.2.2.3 XFER_RDY information unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .99

5.2.2.4 DATA informa tio n u n i t . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99

5.2.2.5 RESPONSE information unit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .100

5.2.3 Sequences of SSP frames . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103

5.2.4 SSP transport layer handling of link layer errors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105

5.2.4.1 COMMAND frame . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105

5.2.4.2 TASK frame . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105

5.2.4.3 XFER_RDY frame. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105

5.2.4.4 DATA frame. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .105

5.2.4.5 RESPONSE fra me. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105

5.2.5 SSP transport layer error handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106

5.2.5.1 SSP target port error handling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .106

5.2.5.2 SSP initiator port error handling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .106

5.2.2.5.1 RESPONSE information unit overview.................................................. 100

5.2.2.5.2 RESPONSE information unit NO_DATA format.................................... 101

5.2.2.5.3 RESPONSE information unit RESPONSE_DATA format......................101

5.2.2.5.4 RESPONSE information unit SENSE_DATA format............................. 102

6.0 Application layer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109

6.1 SCSI application layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109

6.1.1 SCSI transport protocol services. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109

6.1.2 Device server error handling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .109

6.1.3 SC SI mode parameters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109

6.1.4 SC SI log parame ters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

6.1.5 SCSI vital product data (VPD). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .119

6.1.1.1 SCSI transpo rt protocol services overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109

6.1.3.1 Disconnect-Reconnect mode page . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109

6.1.3.2 Protocol-Specific Port mode page . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112

6.1.3.3 Protocol-Specific Logical Unit mode page . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

6.1.4.1 Protocol-Specific log page. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

6.1.3.1.1 Disconnect-Reconnect mode page overview......................................... 109

6.1.3.1.2

6.1.3.1.3

6.1.3.1.4

6.1.3.1.5

6.1.3.2.1 Protocol-Specific Port mode page overview..........................................112

6.1.3.2.2 Protocol-Specific Port mode page - short format................................... 112

6.1.3.2.3 Protocol-Specific Port mode page - Phy Control And Discover subpage114

BUS INACTIVITY TIME LIMIT field .............................. .............111

MAXIMUM CONNECT TIME LIMIT field ................................. 111

MAXIMUM BURST SIZE field...................................................... 111

FIRST BURST SIZE field...............................................................111

Serial Attached SCSI (SAS) Interface Manual, Rev. B iii

List of Figures

Figure 1. Functional scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Figure 2. SCSI client-server model. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Figure 3. SCSI client-server model with service delivery subsystem . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4

Figure 4. Physical links and phys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20

Figure 5. Ports (narrow ports and wide ports) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21

Figure 6. SAS devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Figure 7. Domains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23

Figure 8. Devices spanning SAS domains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24

Figure 9. Edge expander device set. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25

Figure 10. Maximum expander device set topology. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26

Figure 11. Potential pathways . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Figure 12. Multiple connections on wide ports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Figure 13. Reset terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32

Figure 14. Decimal value translation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Figure 15. OOB signal transmission. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .39

Figure 16. OOB signal detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41

Figure 17. SAS to SAS OOB sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43

Figure 18. SAS speed negotiation window. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .44

Figure 19. SAS speed negotiation sequence (phy A: G1, G2, G3, phy B: G2 only). . . . . . . . . . . . . . . . . . 46

Figure 20. SAS speed negotiation sequence (phy A: G1, G2, G3, phy B: G1, G2) that fails. . . . . . . . . . .47

Figure 21. Hot-plug and the phy reset sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .48

Figure 22. Triple primitive sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .58

Figure 23. Redundant primitive sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .59

Figure 24. Elasticity buffers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

Figure 25. Aborting a connection request with BREAK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .84

Figure 26. Connection request timeout example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85

Figure 27. Closing a connection example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .86

Figure 28. Rate matching example. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .87

Figure 29. SSP frame transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .88

Figure 30. Interlocked frames. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .90

Figure 31. Non-interlocked frames with the same tag . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90

Figure 32. Non-interlocked frames with different tags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91

Figure 33. Closing an SSP connection example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92

Figure 34. Task management function sequence of SSP frames . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .103

Figure 35. Write command sequence of SSP frames . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .103

Figure 36. Read command sequence of SSP frames . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104

Figure 37. Bidirectional command sequence of SSP frames . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104

1.0 Interface requirements

1.1 Acknowledgements

The informatio n contained in this publ ication was gathered from many sources. Portions of the tex t used to explain general S AS conc epts were ad apt ed in var ious fo rms, with p ermis sion, fr om th e SCSI Trade Associ ation, Hewett Packard Invent slides, and the T10/1760-D SAS-2 Interface Standard Draft 02.

1.2 How to use this interface manual

This manual provides a description of the Serial Attached SCSI (SAS) interface protocol and some general timing information as implemented by Seagate p roducts. Each individ ual drive’s Product Manual for the various SAS interface products contains additional and more detailed information on protocol, features supported, timing, and electrical/mechanical aspects of how the SAS interface is implemented by that product.

This manual provi des a general, tutorial-ty pe des c ripti on of the A NSI SA S s ystem . It is not intended to g iv e all of the kinds of details needed to design/implement a SAS system or product.

For information about SAS interface details not included herein or in the individual drive product manuals, refer to the specifications listed in Section .

Note. T he individu al drive’s produ ct manual has tables that s pecify w hich SCS I features the drive i mple-

ments, what the default parameters are for the var ious features they imp lemen t, which paramete rs are changeable, and which are not.

Note. SCSI commands are documented in the SCSI Commands Reference Manual, part number

100293068.

The combination of this specif ication to gether with th e SCSI Co mmands Re ference Man ual and d etails in the individual drive’s produc t manual, provides a description of h ow a particular produc t implements the SAS I/O system. This inte rface m anual is in tended to be u sed i n conj uncti on with the i ndividua l dri ve’s produ ct ma nual and the SCSI Commands Reference Manual.

Serial Attached SCSI (SAS) Interface Manual, Rev. B 1

1.2.1 Scope

Figure 1 uses a representative set of specifications to show the functional partitions and the relationships

among SCSI specifications applicable to drives covered by this product manual.

SCSI Architecture Model

(SAM-4)

In ter fa ce S P I-4

SCSI Block Com mands

SCSI Primary Commands

SCSI

In te rloc k e d

Protocol

and

SCSI

P a ralle l

Signaling FC -FS

SBC-3

SPC-4

Fibre

Channel

Protocol FCP -3

Fibre

Channel

Framing &

Serial SCSI

Protocol

and

Serial

Attached

SCSI

Interface SAS-2

Com mands

Protocols

Interconnects

Figure 1. Functional scope

The functional areas define the scope of each as follows:

• SCSI Architecture Model: Defi nes the SCSI systems model, the functional partit ioning of the SCSI set an d requirements applicable to all SCSI implementations and implementation specifications.

• Commands: Implementat ion specifications which define classes inc luding a device model for each class. These specifications specify the required commands and behavior that is common to all devices or unique to a given class of devi ces and presc ribe the rules to be followed by a S CSI initiator port when sendin g com mands to a device.

• Protocols: Imple mentation specific ations whic h define the r ules for exch anging infor mation so that d ifferent SCSI devices can communicate.

• Interconnects: Implementation specifications which define the electrical and signaling rules essential for devices to interoperate over a given physical interconnect.

The diagram of Figure 1 shows how the spe cific ation s listed below fit wit hin each cate gory. The specifications included in the diagram are mean t to serv e as exam ples an d may n ot refle ct the f ull set of specif ications currently in force.

1.2.2 Applicable specifications

The following ANSI speci fications should be referenced for more d etails about SCSI system specificatio ns of operation:

• SCSI Architecture Model-4 (SAM-4), T10/1683-D

• SCSI Enclosure Services - 2 (SES-2), T10/1559-D

• SCSI Block Commands - 3 (SBC-3), T10/xxxx-D

• SCSI Primary Commands-4 (SPC-4), T10/1731-D

• SCSI Serial Attached SCSI - 2 (SAS-2) T10/1760-D Rev 01

• Fibre Channel Protocol for SCSI, Third Version (FCP-3) T10/1560-D

2 Serial Attached SCSI (SAS) Interface Manual, Rev. B

1.2.3 Other references

For information on the current status of the listed documents, or regarding availability, contact the indicated organization.

• SFF-8223, 2.5" Drive Form Factor with Serial Connector

• SFF-8323, 3.5" Drive Form Factor with Serial Connector

• SFF-8523, 5.25" Drive Form Factor with Serial Connector

• SFF-8410, HSS Copper Testing and Performance Requirements

• SFF-8460, HSS Backplane Design Guidelines

• SFF-8470, Multi Lane Copper Connector

• SFF-8482, SAS Plug Connector

1.3 General interface description

This SAS Interface Manual d escrib es the S eagate Technology, Inc. subset of the Seri al Attache d SCSI ( Small Computer Systems Interface) as implemented on the Seagate-built drives. The interface is compatible with the SCSI Interface Specifications listed in S ection 1.2.2 . The drives covered by this product ma nual are classi fied as “Intelligent” peripherals.

1.3.1 Introduction to Serial Attached SCSI Interface (SAS)

The SAS interface provides several advantages over Parallel SCSI. Parallel SCSI has reached a practical maximum transfer ra te of 320 MB/sec . Parallel SCS I is limited to a maximum of 16 devices c onnected to th e bus, one of which must be a host bus adapte r. Fiber Channel (FC) allows SCSI to be transmitted in a serial manner using frame s, rather t han on a parall el bus . It allo ws up to 1 27 devic es to be add ressed on fib re op tic cable, or coppe r conductors. FC devi ces are connected in a loop and arbitrate fo r control of the loop, using fibre optic cable devices may be physically separated by 10km of cable. Pa rallel ATA (PATA) is limited to a maximum of two devices pe r host adapter, lower data transfer rates, and i s not considered intell igent, therefore, not well suited for ente rpris e envi ronme nts. Serial ATA (SATA) increa ses the data transfe r rate but is li mited in addressing, and cable length, and intelligence. SATA uses small form cables and connectors to transfer data at up 300 MB/sec, with the standard allowing transmission of up to 600 MB/sec. Currently SATA is a pointto-point connection inside the computer’s system unit, with a maximum length of 18 inches. External SATA is in the development stage.

SAS combines the intel lige nc e of S CSI wi th th e phy s ical tra nspor t l ayer of Se ri al ATA. This scheme allows th e intelligence of SCSI to be tr ansferred on a serial cable simila r to SATA. Data is transfer in frames, like fiber channel. The initial da ta transfer rate for SAS was 300 MB/sec . with the SAS-2 standard allowing up to 60 0 MB/sec. SAS provi des for full dup lex operation, a t 300 MB/sec. it is possible to attain 600 M B/sec. per pathway. SAS is a point to point connection as is SA TA, Expanders are used to increase the number of devices that may be connected. There are two types of expanders; Edge Expanders that may address 128 physical devices and one other expander, and Fanout Expanders that may addr ess 128 other dev ices or expanders. Theo retically, there may be 16,256 devices in a single SAS domain. Unlike Parallel SCSI and Fibre Channel SAS drives and Serial ATA drives may be attached to the same expander.

1.3.2 The SAS interface

The Seagate SAS inter face des c ribed her ei n co ns is ts of a dua l ported SAS bidirection al l inks . T he SC SI i nterface supports multipl e initiators, d isconnect/reco nnect, self-c onfiguring host software, automati c features tha t relieve the host from the nec essity of k nowing the phys ical architec ture of the target (log ical block addressing is used), and some other miscellaneous features.

Serial Attached SCSI (SAS) Interface Manual, Rev. B 3

Unless specified o therwise in the in dividua l dri ve’s produ ct man ual, th e drive is al ways a S AS targe t port, an d never a SAS initiator por t. For certain commands, which may or may not b e supported by a particular drive model, the drive mu st ac t as a SA S initiator port, but does n ot o therwise do so. For pur po se s of th is s pec if ication, “drive” may be substituted for the word “target” wherever “target” appears.

In the event of a conflict between this document and ANSI SCSI documents, the requirements of the ANSI documents shall apply.

In Figure 2, it can be see n that seve ral “app lica tio n clie nts” from a s ingle initia tor may have o ne or mo re tasks in queue with sev eral “ dev ice servers” in a singl e targe t. A d rive c oul d b e a SC SI target port or it could be one of the device servers as part of som e larger entit y. When reading the description, one need s to be able to put the drive of interest in th e prop er con text in terms of wh at is sho wn in F igure 2. F or a pro per und erstanding of the operation of the SCSI pro tocol, the t erms in th e SCSI ar chitectural model a s described in ANS I specific ation T10/1683-D (SAM -4) should b e well underst ood before r eading ope ration desc riptions in any SCSI document. The SAM-4 spec ification gives a more detailed understanding of some of the new SCSI terminology. Figure 2 shows the SCSI in itiator connected to the SCSI target by the servic e delivery subsystem . The SAS interface provides this function.

Logical

Unit

Application

Client

Device Service Request

Device Service Response

Device

Server

Task Management Request

Task Management Response

Figure 2. SCSI client-server model

Client-Server Transaction

Client

Server Request

Server Response

Protocol Servi ce

SCSI

Interface

Init-

iator

Port

Task

Manager

Target DeviceInitiator Device

Server

SCSI

Tar-

get

Port

Service Delivery Subsystem

Figure 3. SCSI client-server model with service delivery subsystem

4 Serial Attached SCSI (SAS) Interface Manual, Rev. B

1.3.3 Glossary 8b 10b coding—A coding scheme that represents an 8-bit data byte as a 10-bit character. aborted command—A SCSI command that has been ended by aborting the task created to execute it. ACA—Auto Contingent Allegiance (see below). ACA command—A command performed by a task with the ACA attribute. For additional information about the

ACA command, refer to the Seagate SCSI Commands Reference Manual, part number 100293068.

ACK—Acknowledge primitive that specifies the positive acknowledgement of an SSP frame. application client—An object that i s the sour ce of SC SI comma nds. An obj ect in thi s sense i s not a tangi ble

piece of hardware, bu t may b e a si ngle n umeric parameter, such as a logi cal unit nu mber, or a complex ent ity that performs a set of operations or services on behalf of another object (see ANSI SAM-4, T10/1683-D).

auto contingent allegiance—One of the conditions of a task set following the return of a CHECK CONDITION status.

big-endian: A format for storage or transmission of binary data in which the most significant byte appears first. In a multi-byte value, th e byte containing the most s ignificant bit is stor ed in the lowest memo ry address and transmitted first and the byte containing the least signific ant bit is stored in the highes t memory address and transmitted last (e.g., for the value 0080h, the byte containing 00h is stored in the lowest memory address and the byte containing 80h is stored in the highest memory address).

blocked (task state)—The state of a task that is prevented from completing due to an ACA condition. broadcast primitive processor (BPP)—An object within an expander function that manages broadcast primi-

tives.

burst time—The part of an OOB signal (see 3.4) where ALIGN primitives (see 4.2.5.2) are being transmitted. byte—A sequence of eight contiguous bits considered as a unit. call—The act of invoking a procedure. character—A sequence of te n contiguous bits considered as a unit. A byte is encoded as a characte r using

8b10b coding. client-server—A relationship established between a pair of distributed objects where one (the client) requests

the other (the server) to perform some operati on or unit of work on th e client’s behalf (see ANS I SAM-2, T10 / 1157D).

Client—An object that requests a service from a server. command—A request describing a unit of work to be performed by a device server. command descriptor block (CDB) —A structure use d to communicate a comm and from a SCSI applicatio n

client to a SCSI device server. See SAM-4. completed command—A command that has ende d by retur ni ng a status and s ervi ce resp ons e of Task Com-

plete or Linked Command Complete. completed task—A task that has ended by r eturning a status and service r esponse of Task Complete. The

actual events comprising the Task Complete response are protocol specific. configurable expander device—An expander device that contains an expander route table that is confi gu re d

with expander route entries. confirmation—A response returned to an object, which signals the completion of a service request.

Serial Attached SCSI (SAS) Interface Manual, Rev. B 5

confirmed service—A service av ai lab le at th e p ro toc ol s er v ice interface, which req uires co nfi rm ati on of c ompletion. The confirm ed s ervi ce consists of the request and co nfi rm ati on st eps an d op tion al ly the indi c atio n an d response steps.

connection—A temporary association between a SAS initiator port and a SAS target port. connection rate—The effective rate of dwords thro ugh the pathway between a S AS initiator phy a nd a SAS

target phy, established through the connection request.

control character (Kxx.y)—A character that does not represent a byte of data. control mode page—The mode page that identifies the settings of se veral device ser ver behaviors that may

be of interest to an application client or may be changed by an application client. The complete definition of the Control mode page is found in the Seagate SCSI Commands Reference Manual, part number 100293068.

current task—A task that is in the process of sending messages, sending status, transferring data, or transferring command data to or from the initiator.

cyclic redundancy chec k (CRC)—An error detec ting code used to detect the validity of data that has been transferred during the current data group.

data character (Dxx.y)—A character representing a byte of data. data dword—A dword that starts with a Dxx.y (data character). data field—The portion of a data group that contains data bytes. data group—A sequence of data bytes and the f our pC RC b yte s dur in g a DT DATA IN PHASE or a DT DATA

OUT PHASE that starts at the first byte of the DT DATA phase or at the first byte after the last pCRC byte. data group transfer—Parallel transfers that t ransfer d ata and pCRC i nform ation us ing only data gro ups. The

last four bytes of a data group transfer contain CRC information over the whole data group.

D.C. idle—A differential signal level that is nominally 0 V(P-P). deadlock—A condition in which two or mor e processe s (e.g., connec tion reques ts) are waiting on each ot her

to complete, resulting in none of the processes completing. destination device—The SCSI device to which a service delivery transaction is addressed. See source

device. deterministic jitter—Jitter with a non-Gaussian probability density function. Deterministic jitter is always

bounded in amplitude and has specific causes. Four kinds of deterministic jitter are identified: duty cycle distortion, data dependent, sinusoi dal, and uncorrelated (to the data) bounded. Deterministic jitt er is characterized by its bounded, peak-to-peak value.

device name— A worldwide unique name for a device within a transport protocol. device server—An object within a SAS target device that processes SCSI tasks (see SAM-3). device service request—A request, submitted by an application client, conveying a SCSI command to a

device server. device service response—The response returned to an application client by a device server on completion of

a SCSI command. differential—A signalling alternative that empl oys di fferential (tw o com pleme ntary signals ) drivers and rec eiv-

ers to improve signal-to-noise ratios and increase maximum cable lengths.

direct current (D.C.)—The non-A.C. component of a signal. In this, all frequency components below 100 kHz. discover process—The algorithm u sed by a management applicati on client to configure the SAS domain.

See SAS.

6 Serial Attached SCSI (SAS) Interface Manual, Rev. B

disparity—The difference between the number of ones and zeros in a character. domain—A SAS domain, a SCSI domain, or an ATA domain. dword—A sequence of four contiguous bytes or four contiguous characters considered as a unit. The meaning

depends on the context (e.g., when discussing the bits being transmitted over a physical link, dword represents four characters (i .e., 40 bits). When disc ussing the c ontents of a fr ame a fter 10b8b decod ing (se e 3.2) , dword represents four bytes (i.e., 32 bits)).

dword synchronization—Detection of an incoming stream of dwords from a physical link by a phy. edge expander device—An expander device that is part of a single edge expander device set. edge expander device set—A group of one or more edge expander devices that may be attached to no more

than one other edge expander device set or one fanout expander device. enabled (task state)—The state of a task th at m ay comp lete at any time. Alterna t ivel y, the state of a task that

is waiting to receive the next command in a series of linked commands.

end device—A SAS device that is not contained within an expander device. ended command—A command that has completed or aborted. event notification— A message passed from the transport layer to the applic ation layer notifying t he applic a-

tion layer that a SCSI event has occurred. See SAM-4. exception condition—Any event that causes a SC SI d evice to e nter an auto co ntinge nt alle gian ce or c ontin-

gent allegiance condition. expander device—A device that is part of the service delivery subsystem and facilitates communication

between SAS devices. expander function—An object within an expander device that contains an expander connection manager,

expander connection router, and broadcast primitive processor.

expander phy—A phy in an expander device that interfaces to a service delivery subsystem. expander port—An expander device object that interfaces to the service delivery subsystem and to SAS ports

in other devices.

expander route entry—A routed SAS address and an enable/disable bit in an expander route table. expander route index—A value used in combination with a phy id entif ier to sele ct an expan der route entr y in

an expander route table. fanout expander device—An expander device that is capable of being attached to two or more edge

expander device sets.

faulted initiator—The initiator to which a Command Terminated or CHECK CONDITION status was returned. faulted task set—A task set that contained a faulting task. faulting command—A command that completed with a status of Check Condition or Command Terminated. faulting task—A task that has completed with a status of Check Condition or Command Terminated. field—A group of one or more contiguous bits. frame—A sequence of data dwords betwee n a start of frame pri mitive (e.g., SO F, SOAF, or SATA_S OF) and

an end of frame primitive (e.g., EOF, EOAF, or SATA_EOF).

hard reset—A SAS device or expander device action in response to a reset event. Hard reset sequence—A sequence that causes a hard reset.

Serial Attached SCSI (SAS) Interface Manual, Rev. B 7

hardware maximum physical link rate—The maximum physical link rate capability of a phy. hardware minimum physical link rate—The minimum physical link rate capability of a phy. hash function—A mathematical function that maps values from a larger set of values into a smaller set of val-

ues, reducing a long value into a shorter hashed value.

identification sequence—A sequence where phys exchange IDENTIFY address frames. idle dword—A vendor-specific data dword that is scrambled and is transmitted outside a frame. idle time—The part of an OOB signal where D.C. idle is being transmitted. implementation-specific—A requireme nt or feature th at is defined in a S CSI bu t whose im pleme ntation may

be specified by the system integrator or vendor. implementation option—An option whose actualization within an imple mentation is at the discretion of the

implementor. indication—A message passed from a lower layer state machine to a higher layer state machine, usually

relaying a request (see ) from a peer higher layer state machine. information unit (IU)—The portion of an SSP fram e that car ries comma nd, task manag ement fu nction, data,

response, or transfer ready information. information unit tr ansfer—Pa rallel tran sfers that transfe r data, status, commands, task attribut es, task man-

agement information, acrid, and nexus information using only SPI information units. initiator—A SCSI device containing applicatio n clients which originate dev ice service and task ma nagement

requests to be processed by a SCSI target port SCSI device. invalid dword—A dword with an illegal character, with a control character in other than the first character posi-

tion, with a control character other than K28.5 or K28.3 in the first character position, or with a running disparity error.

I/O operation—An operation defin ed by an u nlink ed SCS I com mand, a seri es of li nked S CSI c ommand s or a task management function.

I/O process—An I/O proc ess consi sts of one initial connectio n or, if information units are e nabled, the establishment of a nex us, and a zero or more ph ysical or logical rec onnection all pertaining to a single task or a group of tasks. An I/O process begins wi th the establishm ent of a n exus. If th e SPI info rmation unit transfers are disabled, an I/O pr ocess no rmally end s with a C ommand Com plete mes sage. If info rmation u nit transfe rs are enabled, an I/O process ends with a SPI L_Q info rm ation un it with the type field set to status and the Data Length field set to zero.

I_T nexus—A nexus that exists between a SCSI initiator port and a SCSI target port. I_T nexus loss—A condition where a SAS port determines that another SAS port is no longer available. I_T_L nexus—A nexus that exists between a SCSI in itiator port, a SCSI target port, and a lo gical unit. This

relationship extends the prior I_T nexus. I_T_L_Q nexus—A nexus between a S CSI in itiato r port, a SCS I target p ort, a logica l uni t, and a tagged task .

This relationship extends the prior I_T nexus or I_T_L nexus.

jitter—Abrupt and unwanted variations in the interval between successive pulses. layer—A subdivision of the architecture constituted by subsystems of the same rank. least significant bit (LSB)—In a binary code, the bit or bit positio n with the sm allest numeric al weighti ng in a

group of bits that, when taken as a whole, represen t a numeri cal va lue (e.g., in the num ber 0001b, th e bit that is set to one).

8 Serial Attached SCSI (SAS) Interface Manual, Rev. B

linked CDB—A CDB with the link bit in the control byte set to one. linked command—One in a series of SCSI comman ds execu ted by a si ngle task, whic h coll ectiv ely make up

a discrete I/O operati on. In such a series, ea ch co mmand has the same task identifier, and all except t he last have the link bit in the CDB control byte set to one.

link reset—Performing the link reset sequence link reset sequence—For SAT A, a phy reset sequence. For SAS, a phy reset sequence followed by an identi-

fication sequence, or a phy reset sequen ce followed by a hard reset seque nce, another phy reset sequence, and an identification sequence.

little-endian—A format fo r storage or transmi ssion of binary data in whic h the least signific ant byte appears first. In a multi-byte v alue, the byte co ntaining the least s ignificant bit i s stored in the lowest memory address and transmitted f irst and the byte containing the m ost significant bit is stored i n the highest memory address and transmitted last (e.g., for the value 0080h, the byte containing 80h is stored in the lowest memory address and the byte containing 00h is stored in the highest memory address).

livelock—A condit ion where two o r more pr ocess es (e.g., co nnection reque sts) co ntinually chan ge thei r state in response to changes in other processes, resulting in none of the processes completing.

logical connect—Establishes an I_T_L_Q nexus using SPI L_Q information units. logical disconnect—Reduces the current I_T_L_Q nexus to an I_T nexus. logical reconnect—Reestablishes an I_T_L_Q nexus from an I_T nexus using SPI L_Q information units. logical unit—a SCSI target port-reside nt entity which implements a device model and exec utes SCSI com-

mands sent by an application client.

logical unit number—A 64-bit identifier for a logical unit. logical unit option—An option pertaining to a logical unit, whose actualization is at the discretion of the logical

unit implementor.

lower level protocol—A protocol used to carry the information representing upper level protocol transactions. media—Particular ele ments comprising the intercon nect including copper c ables, printed circuit boar ds, and

other transmission line materials. media information—Informatio n store d within a SCSI d evice whic h is n on-volatil e (retained through a po wer

cycle) and accessible to a SCSI initiator port through the execution of SCSI commands.

message—Information sent between state machines. most significant bit (MSB)—In a binary code, the bi t or bit pos ition wit h the larges t numerica l weighti ng in a

group of bits that, when taken as a whole, represen t a numeri cal va lue (e.g., in the num ber 1000b, th e bit that is set to one).

multidrop—A characteristic of the SCSI bu s that allo ws SCSI devices to be connecte d to the SCSI bu s without disrupting the electrical path between the terminators.

multimode single-ended (MSE)—A signalling alternative for multimode SCSI devices that employs MSE drivers and receivers to allow multimode SCSI devices to operate when SE SCSI devices are present on the bus.

NAK—Specifies the negative acknowledgement of an SSP frame and the reason for doing so. narrow link—A physical link that attaches a narrow port to another narrow port. narrow port—A port that contains exactly one phy. negotiated physical link rate—The current operational phy sical lin k rate estab lished after sp eed nego tiation

between two phys.

Serial Attached SCSI (SAS) Interface Manual, Rev. B 9

nexus—A relat ionship between a SCSI initia tor port and a SCSI target port, lo gical unit, or queue tag that begins with an ini tia l co nne ction and ends wit h t he co mpl eti on of th e associated I/O pr oces s. T hi s rel ati ons hip is formed as the result of a task.

object—An architectural abstraction or “container” that encapsulates data types, services, or other objects that are related in some way.

OOB sequence—A sequence where two phys exchange OOB signals. OOB signal—Pattern of ALIGNs and idle time used during the link reset sequence. partial pathway—The set of physical li nk s part icipa tin g in a co nnec ti on r eq ues t which has not r ea ch ed a S AS

endpoint (i.e., the connection request has been transmitted by the source device and confirmed as received by at least one expander device with AIP).

pathway—A set of physical links b etween a SAS initiator phy and a SAS target ph y being us ed by a connection.

pathway blocked count—The num ber of times the po rt has retried this c onnection request due to receivin g OPEN_REJECT (PATHWAY BLOCKED).

pending task—A task that is not a current task. phy—A device object that is used to interface to other devices. phy reset sequence—An OOB sequence (see ) followed by a speed negotiation sequence (see ). physical link—Two differential signal pairs, one pair in each direction, that connect two physical phys. physical phy—A phy (see ) that contains a transc eiv er and el ectr ic ally inte r fac es t o a phys ic al lin k to c om mu-

nicate with another physical phy.

port—A SAS port or an expander port. Each port contains one or more phys. potenti al pathway—A set of physical links between a SAS initiator phy and a SAS target phy. power on—Power being applied. primitive—A dword starting with K28.5 or K28.3 followed by three data characters. primitive sequence—A set of primitives treated as a single entity. procedure—An operation that can be invoked through an external calling interface. programmed maximum physical link rate—The maximum oper ational physical link rate of a phy (e.g., as

programmed via the SMP PHY CONTROL function (see SAS) or the Phy Control and Discover subpage. programmed minimum physical link rate—The minimum operational physical link rate of a phy (e.g., as pro-

grammed via the SMP PHY CONTROL function (see SAS), the Phy Control and Discover subpage. protocol—The rules governing the conten t and exchange of informatio n passed between distributed obje cts

through the service delivery subsystem.

protocol option—An option whose definition within a SCSI protocol is discretionary. protocol service confirmation—A signal fr om the lower level pro tocol service lay er notif ying the up per l ayer

that a protocol service request has completed. protocol service indication—A signal from the lower level protocol service layer notifying the upper level that

a protocol transaction has occurred. protocol service request—A call to the lo wer le ve l protoc ol s er vic e l ay er to begin a protocol s ervi ce transac-

tion.

10 Serial Attached SCSI (SAS) Interface Manual, Rev. B

protocol service response—A reply from the upper level protocol layer in response to a protocol service indication.

queue—The arrangement of tasks within a task set, usually according to the temporal order in which they were created. See task set.

queue tag—The parameter associated with a task that uni que ly id enti fi es it f ro m ot her tagged tasks for a log ical unit from the same initiator.

random jitter—Jitter that is assumed to have a Gaussian distribution. rate—Data transfer rate of a physical link (e.g., 1,5 Gbps or 3,0 Gbps). rate change delay time (RCDT)—The time between rates during the speed negotiation sequence. receiver—The recipient of a signal. reflection coefficient (r)—The reflection coefficient o f the transmission media (i.e., the ratio of the reflecte d

voltage divided by the voltage applied to the transmission media). request—A message passed fr om a high er l ayer s tate mac hin e to a lowe r la yer state mac hine , usua lly to in i-

tiate some action. request-response transaction—An interaction between a pa ir of d istributed , cooper ating ob jects, co nsisting

of a request for service submitted to an object followed by a response conveying the result. request-confirmation transaction—An interaction between a pair of cooperating objects, consisting of a

request for service submitted to an object followed by a response for the object confirming request completion.

reset event—An event that triggers a hard reset from a SAS device. response—A message passed from a high er layer state machine to a lower layer state machine, usua lly in

response to an indication. running disparity—A binary value indicat ing the cu mulative en coded si gnal imb alance be tween the on e and

zero signal state of all characters since dword synchronization has been achieved. SAS address— worldwide unique nam e assigned to a S AS initiator port, SAS target port, ex pander device,

SAS initiat or device, or SAS target device (see 2.2.2).

SAS device—A SAS initiator device, SAS target device, or SAS target/initiator device. SAS domain—The I/O system defined by this that may serve as an ATA domain and/or a SCSI domain. SAS initiator device—A device containing SSP, STP, and/or SMP initiator ports in a SAS domain. SAS initiator phy—A phy in a SAS initiator device. SAS initiator port—An SSP initiator port, STP initiator port, and/or SMP initiator port in a SAS domain. SAS phy—A phy in a SAS device that interfaces to a service delivery subsystem. SAS port—A SAS initiator port, SAS target port, or SAS target/initiator port. SAS target device—A device containing SSP, STP, and/or SMP target ports in a SAS domain. SAS target phy—A phy in a SAS target device. SAS target port—An SSP target port, STP target port, and/or SMP target port in a SAS domain. SAS target/initiator device—A device that has all the characteristics of a SAS target device and a SAS initia-

tor device.

Serial Attached SCSI (SAS) Interface Manual, Rev. B 11

SAS target/initiator port —A port that has all the characteristics of a SAS target port and a SAS initiator port in a SAS domain.

scrambling—Modifying data by XORing each bit with a pattern generated by a linear feedback shift register to minimize repetitive character patterns.

SCSI application layer—The proto cols and procedures tha t implement or invoke S CSI commands and task management functions by using services provided by a SCSI protocol layer.

SCSI device—A device that contains one or m ore SCSI ports that are con nected to a service delivery subsystem and supports a SCSI application protocol. See SAM-4.

SCSI domain—An I/O system consisting of a set of SCSI devices that communicate with one another by means of a serv ice delivery subsystem. See SAM-4 .

SCSI initiator device—A SCSI dev ice containing application cl ients and SCSI initiator por ts that originates device service and task management r equests to be proc essed by a SCS I target devic e and receives device service and task management responses from SCSI target devices. See SAM-4.

SCSI initiator port—A SCSI initiator device object that acts as the connection between application clients and the service delivery subsystem through which indications and responses are routed. See SAM-4.

SCSI port—A SCSI initiator port or a SCSI target port. See SAM-4. SCSI target device—A SCSI device containing logical units and SCSI target ports that receives device service

and task management reques ts for process ing and send s device service an d task managemen t respons es to SCSI initiator devices. See SAM-4.

SCSI target port—A SCSI target device object that contains a task router and acts as the connection between device servers and task mana gers and the ser vice del ivery s ubsystem through whi ch reques ts and c onfirmations are routed. See SAM-4.

SCSI target/initiator device—A device th at has all the ch ar ac teris ti cs of a SCS I target devi ce a nd a SC SI in itiator device. See SAM-4.

SCSI target/initiator port—A SCSI targe t/initiator devic e object that has all th e char acteristics of a S CSI target port and a SCSI initiator port. See SAM-4.

sender—A client or server that originates a service delivery transaction. Serial ATA Tunneled Protocol (STP)—The protocol defined in thi s used by STP init iator ports to communi-

cate with STP target ports in a SAS domain.

Serial Attached SCSI (SAS)—The set of protocols and the interconnect defined by this manual. Serial Management Protocol (SMP)—The protocol defined in this used by SAS devices to communicate

management information with other SAS devices in a SAS domain. Serial SCSI Protocol (SSP)—The protocol defined in this used by SCS I initiator ports to communic ate with

SCSI target ports in a SAS domain.

server—A SCSI object that performs a service on behalf of a client. service—Any operation or function performed by a SCSI object, which can be invoked by other SCSI objects. service delivery failure —Any non-recoverable error causing t he corruption or loss of one or more ser vice

delivery transactions while in transit. service delivery port— A device-re sident interf ace used by the app lication cl ient, device server or task m an-

ager to enter and r etrieve requests and responses f rom the service delivery sub system. Synonymous with “port.”

12 Serial Attached SCSI (SAS) Interface Manual, Rev. B

service delivery subs yst em— Th e part of a S CSI I/O s ystem tha t tran sm its in for ma tio n between a SCSI initiator port and a SCSI target por t, or the part of an ATA I/O system that transmits inf ormation betw een an ATA host and an ATA device, or the part of a SAS I/O system that transmits information between a SAS initiator port and a SAS target port.

service delivery transaction—A request or response sent through the service delivery subsystem. signal—(n) A detectable asynch ronous event possibly accompanied by descriptive data and parameters. (v)

The act of generating such an event.

single transition (ST)—The latching of data only on the assertion edge of the REQ or ACK signals. SMP init iator phy—A SAS initiator phy in an SMP initiator port. SMP initiator port—A SAS initiator device object in a SAS domain that interfaces to the service delivery sub-

system with SMP.

SMP phy—A SAS phy in an SMP port. SMP port—An SMP initiator port, SMP target port, or SMP target/initiator port. SMP target phy—A SAS target phy in an SMP target port. SMP target port—A SAS target de vice object in a SAS domain that interfaces to t he service delivery sub-

system with SMP. SMP target/initiator port—A port that has all the ch aracteristics of an SMP ini tiator port and an SMP target

port.

source device—The SCSI device from which a service delivery transaction originates. See destination device. speed negotiation lock time (SNLT)—T he m aximu m time du ring a spee d nego tiation windo w for a tr ansm it-

ter to reply with ALIGN (1).

speed negotiation sequence—A sequence in which two phys negotiate the operational physical link rate. speed negotiation transmit time (SNTT)—The time du ri ng w hic h ALIG N (0 ) or ALI GN (1) is trans mi tted dur-

ing the speed negotiation sequence. spread spectrum clocking— The technique of modulating the operati ng frequency of a transm itted signa l to

reduce the measured peak amplitude of radiated emissions.

SSP initiator phy—A SAS initiator phy in an SSP initiator port. SSP initiator port—A SCSI initiator port in a SAS domain that implements SSP. SSP phy—A SAS phy in an SSP port. SSP port—An SSP initiator port, SSP target port, or SSP target/initiator port. SSP target phy—A SAS target phy in an SSP target port. SSP target port—A SCSI target port in a SAS domain that implements SSP. SSP target/initiator port—A port that has all the characteristic s of an SSP initiator port an d an SSP target

port.

STP initiator phy—A SAS initiator phy in an STP initiator port. STP initiator port—A SAS initiator device object in a SAS domai n that interfac es to the service deliver y sub-

system with STP. STP phy—A SAS phy in an STP port.

Serial Attached SCSI (SAS) Interface Manual, Rev. B 13

STP port—An STP initiator port, STP target port, or STP target/initiator port. STP target phy—A SAS target phy in an STP target port. STP target port—A SAS target device object in a SAS domain that interfaces to the service delivery s ub-

system with STP. STP target/initiator port—A port that has all the c haracteristics of an STP initi ator port and an STP target

port. STP/SATA bridge—An expander device object containing an STP target port, a SATA hos t port , and the fun c-

tions required to forward inform ation betwe en the STP target port and S ATA host port to enab le STP ini tiator ports in a SAS domain to communicate with SATA devices in an ATA domain.

subsystem—An element in a hierarchically part itioned system which i nteracts directly only wi th elements in the next higher division or the next lower division of that system.

subtractive routing attribute—The attribute of an edge expander phy that indicates it may be used by the expander connection ma nager to route connection re quests not resolved using the d irect routing method or table routing method.

subtractive routing method—The method the expander connection manager uses to route connection requests not resolved using the direct routing method or table routing method to an expander device.

suspended information—Information stored within a logical unit that is not available to any pending tasks. table routing attribute—The attribute of an expander phy that indicates it may be used by the expande r con-

nection manager to route connection requests using an expander route table. table routing method—The method the expander connection manager uses to route c onnection reque sts to

an expander device using an expander route table. target—A SCSI device which receives SCSI com mands and directs such command s to one or more logical

units for execution. task—An object withi n the logical unit representing the wor k associated with a command or group of linked

commands. A task consists of one initial connection and zero or more physical or logical reconnections, all pertaining to the task.

task abort event—An event or condition indicating that the task has b een aborted by me ans of a task management function.

task address—a SCSI in itiator port identifies a task to a SCSI target port using a Task Addr ess. The Task Address object repr esen ts either a Tagged Task Address or an Untagged Task Address without regard for the tagged or untagged nature o f the Task. A Tagged Task Address is composed of a Log ical Unit Ide ntifier and a Tag. An Untagged Task Address is composed of a Logical Unit Identifier.

task completion event—An event or condition indicati ng that the task h as ended with a s ervice respons e of Task Complete.

task ended event—An event or condition indicating that the task has completed or aborted. task management function—A task manager service which can be invoked b y an appli cation c lient to affect

the execution of one or more tasks. task management request—A request submitted by an appl ication clie nt, inv oking a task man agement func-

tion to be executed by a task manager. task management response—The response returned to an applica tion client by a task mana ger on co mple-

tion of a task management request. task manager—A server within the target which executes task management functions.

14 Serial Attached SCSI (SAS) Interface Manual, Rev. B

task set—A group of tasks within a SC SI target port device , whose interaction i s dependent on the que uing and auto contingent allegiance rules

task slot—Resources within the logical unit that may be used to contain a task. task tags—A Tag is a field containing up to 64 bits that is a component of a Tagged Task Identifier. A SCSI ini-

tiator port assigns tag values in each Tagged Task Identifier in a way that ensures that the identifier uniqueness requirements stated in ANSI SAM-4, T10/1683-D, Section 4.9, are met.

third-party command—A SCSI command whic h re quire s a l ogi ca l uni t wit hin the target dev ice to as su me th e initiator role and send a SCSI command to a SCSI target port device.

total jitter—Measured jitter including deterministic jitter and random jitter. transaction—A cooperative interaction between two objects, involving the exchange of information or the exe-

cution of some service by one object on behalf of the other.

transceiver—An object that contains both transmitter and receiver objects. transmitter—The source or generator of a signal.

transmitter compliance transfer function (TCTF)—The mathematical statement of the transfer function through which the transmitter shall be capable of producing acceptable signals as defined by a receive mask.

transport protocol service confirmation—A message passed from the transport layer to the application layer (i.e., from the SSP initiator port to the SCSI application client) t hat notifies the applicati on layer that a SCSI transport protocol service has completed.

transport protocol service indication—A message passed from the transport layer to the app lication layer notifying the applicat ion lay er (i.e ., from th e SSP target port to the SCSI de vice serv er) to be gin a SCS I tran sport protocol service.

transport protocol service request—A message passed from the SCSI ap plication layer to the SSP tran sport layer (i.e., from the SCSI application client to the SCS I initiator port) to begin a SCSI tr ansport protocol service.

transport protocol service response—A message passed from the applicati on layer to the transpor t layer (i.e., from the SCSI device server to the SSP target port) that completes the SCSI transport protocol service.

unit inte rval (UI)—The time requir ed to transmit one bit on a physical link (e.g., 666,6 333,3

ps at 3,0 Gbps).

unlinked command—A SCSI command having the link bit set to zero in the CDB control byte. upper level protocol—An application-specif ic protocol execute d through services provided by a lower level

protocol.

valid dword—A dword that is not an invalid dword. virtual phy—A phy (see ) that interfaces to another virtual phy inside the same device. wide link—A group of physical links that attaches a wide port to another wide port. wide port—A port that contains more than one phy.

ps at 1,5 Gbps and

Serial Attached SCSI (SAS) Interface Manual, Rev. B 15

1.3.4 Keywords

Several keywords are used to differentiate between different levels of requirements and optionality, as follows:

vendor-specific—Specification of the referenced item is determined by the device vendor. protocol-specific—Implementation of the referenced item is defined by a SCSI protocol (see Section .) expected—A keyword used to describe the behavior of the models specified by this. ignored—A keyword used to describe an unused bit, byte, word, field or code value. The contents or value of

an ignored bit, byte, word, field or co de v al ue is no t exa mi ned by th e re ce iv in g SCS I devi ce and ma y be set to any value by the transmitting SCSI device.

invalid—A keyword us ed to desc ribe an ille gal or u nsupp orted bit, by te, word, field , or c ode v alue. Receipt o f an invalid bit, byte, word, field, or code value shall be reported as an error.

mandatory—A keyword indicating items required to be implemented as defined by this. may—A keyword that indicates flexibility of choice with no implied preference (equivalent to “may or may not”). may not—Keywords that indi cates flexibilit y of choice with no i mplied preference (equivalent to “ may or may

not”). obsolete—A keyword indica ting item s that were defined in prior SC SI specifica tions but h ave been removed

from this. option, optional—Keywords that describe features which are not required to be implemented by this. How-

ever, if any optional feature defined by the is implemented, it shall be implemented as defined by the. reserved—A key word r eferring to bits, bytes, words, fie lds, and code v alues that a re set aside for fut ure iza-

tion. Their use and interpretation may be specified by future extensions to this or other specifications. A reserved bit, byte, word, or field shall be set to zero, or in accordance with a future extension to this. Recipients are not required to check reserved bits, bytes, words, or fields for zero values. Receipt of reserved code values in defined fields shall be treated as an error.

shall—A keyword i ndicating a m andatory re quirement. De signers a re required to impleme nt all such mandatory requirements to ensure interoperability with other conformant products.

should—A keyword indicating flexibility of choice with a strongly preferred alternative. Equivalent to the phrase “it is recommended.”

16 Serial Attached SCSI (SAS) Interface Manual, Rev. B

1.4 Physical interface characteristics

The physical interface characteristics (ca bles, connectors, electrical descriptio ns, etc.) for the drives cove red by this Interface Manua l are found in each indiv idual drive’s product ma nual since these feat ures are not the same for all drives.

1.5 Bit and byte ordering

A field in a table that consis ts of more than one bit containin g a single v alue ( e.g., a nu mber), the least s ignificant bit (LSB) is shown on the right and the most significant bit (MSB) is shown on the left (e.g., in a byte, bit 7 is the MSB and is sh own on the left; bit 0 is the LS B and is shown on th e right). The MSB and L SB are not labeled if the field consists of 8 or fewer bits.

In a field in a table consisting of more than one byte that contains a single value (e.g., a number), the byte containing the MSB is stored at the lowest address and the byte containing the LSB is stored at the highest address (i.e., big-endian byte ordering). The MSB and LSB are labeled.

Note. SATA numbers bits within fields the same as this standard, but uses little-endian byte ordering. In a field in a table consisting of more than one byte that contains multiple fields each with t heir own values

(e.g., a descriptor), there is no MSB and LSB of the field itself and thus there are no MSB and LSB labels. Each individual field has an MSB and LSB, but they are not labeled.

In a field containing a text string (e.g., ASCII or UTF-8), the MSB label is the MSB of the first character and the LSB label is the LSB of the last character.

A data dword consists of 32 bits. Table 1 shows a data dword containi ng a single valu e, where the MSB is on the left in bit 31 and the LSB is on the right in bit 0.

Table 1. Data dword containing a value

3130292827262524232221201918171615141312111

09876 543210

MSB Value LSB

Tabl e 2 shows a d ata dwor d c ontaining fo ur one -byte fields, where byte 0 (t he fir st b yte) i s on the le ft and byt e 3 (the fourth byte) is on the right. Each byte has an MSB on the left and an LSB on the right.

Table 2. Data dword containing four one-byte fields

3130292827262524232221201918171615141312111

09876543210

MSB Byte 0

(First byte)

LSB MSB Byte 1

(Second

byte)

LSB MSB Byte 2

(Third byte)

LSB MSB Byte 3

(Fourth byte)

LSB

Serial Attached SCSI (SAS) Interface Manual, Rev. B 17

18 Serial Attached SCSI (SAS) Interface Manual, Rev.B

2.0 General

2.1 Architecture

2.1.1 Architectu re overv iew

A SAS domain (see 2.1.7) contains two or more SAS devices and a service delivery subsystem. A SAS domain may support three transport protocols:

a. Serial SCSI Protocol (SSP): a mapping of SCSI supporting multiple initiators and targets; b. Serial ATA Tunneled Pro tocol (STP): a mapping of Seria l ATA expanded to support multiple initiators

and targets; and

c. Serial Management Protocol (SMP): a management protocol.

Drives described i n this manual suppor t only SSP (see SAM- 4). For a descriptio n of STP and SMP se e the SAS standard.

A SAS device (see 2.1.4) contains one or more SAS ports (see 2.1.3). A SAS device may be a SC SI device (see SAM-4). The drives supported by this manual have two ports.

A SAS port (se e 2.1.3) contains one or more phys (se e 2.1.2) . A SAS p ort may be a S CSI port (see SA M-4). The drives supported by this manual have one phy per port.

The service deliver y subsystem (see 2.1.6) in a SAS domain may con tain expander devices to increase th e number of SAS devices supported (see 2.1.5).

Expander devices con tain expander ports (see 2.1.3) and one SMP port. The SM P port is used fo r discovery and configuration of the expander.

An expander port contains one or more phys (see 2.1.2). An expander device shares its phys with the SAS device(s) contained within the expander device.

2.1.2 Physical links and phys

A physical link is a set of four conductor s used as two differenti al signa l pairs. One differen tial signa l transm its in one direction while the other differential signal transmits in the opposite direction. Data may be transmitted in both directions simultaneously.

A physical phy (Phy) conta ins a transceiver which electric ally interfaces to a physica l link, which attaches to another physical phy.

Phys are contained in ports (see 2.1.3). Phys interface to the service delivery subsystem (see 2.1.6). Figure 4 shows two phys attached with a physical link.

Serial Attached SCSI (SAS) Interface Manual, Rev.B 19

PortPort

Phy

Phys ic al link

Different ial s ignal pair

transmitter

-Signal

+Signal

Different ial signal pair

receiver

-Signal

+Signal

Opt ion of more

Phys

Figure 4. Physical links and phys

Phy

Transc eiverTransc eiver

receiver

transmitter

An attached phy is the phy to which a phy is attached over a physical link. A device may contain one or more phys. Each phy is assigned a phy identifier which is unique within the

device. Each phy has a SAS address, inherited from the SAS port or expander. Phys transmit and re ceiv e b its at ph ys ic al li nk ra te. The physical link rates s up por ted by a phy are s pe ci fie d or

indicated by the

WARE MAXIMUM PHYSICAL LINK RATE field, the PROGRAMMED MINIMUM PHYSICAL LINK RATE field, and the PRO- GRAMMED MAXIMUM PHYSICAL LINK RATE field in the SMP DISCOVE R function, S MP PHY CONT ROL function ,

NEGOTIATED PHYSICAL LINK RATE field, HARDWARE MINIMUM PHYSICAL LINK RATE field, the HARD-

and Phy Control and Discover subpage. The bits are part of dwords (4 bytes), each of which has been encoded using 8b10b coding into four 10-bit characters.

2.1.3 Ports (narrow ports and wide ports)

A port contains one or more phys. Ports in a device are asso ciate d with physica l phys based on the ide ntific ation sequence.

A port is created from a set of physical phys if one or more physical phys contained within a device:

a. transmit the same SAS address (see 2.2) during the identification sequence; and b. receive the same SAS addre ss during th e identificati on sequenc e (i.e., the corre sponding attach ed phy

or phys transmit the same SAS address).

A wide port is created if there is more than one ph y in the port. A narr ow port is a port with onl y one phy. The drives supported by this manual implement narrow ports.

A wide link is the set of physi c al l inks that a ttach a wid e po rt to anot her wid e por t. A narr ow li nk is the ph ys ic al link that attaches a narrow port to another narrow port.

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