1. SATA Protocol Training
August 28, 29, 2006

2. Agenda SATA Introduction 30 minutes Steve
SATA Protocol minutes Eric
Layer Architecture
Link Layer
Physical Layer
Phy Layer
Frames and the Transport Layer
SATA II
Bus Doctor SATA Analyzer Demo 30 minutes Eric
Q&As minutes

3. Introduction
August 28, 29, 2006

4. Before SAS/SATA
Early 2000 and there are two main non-networked storage drive standards (i.e. Fibre Channel)
ATA/IDE
The most pervasive storage standard in the world (desktop or enterprise)
Renamed to PATA after the introduction of SATA
18” internal cabling
Host controls a master and slave drive
SCSI
HBA controls up to 15 drives
Used on high-performance workstations, servers, and high-end peripherals; and RAID arrays
U320 is the end of the road for this parallel interface
Host Bus Adapter (HBA) utilizing DMA for maximum I/O
Fibre Channel, ATAPI and SAS have their roots and legacy in SCSI

5. History of Parallel ATA
Generation
Standard
Year
Speed
Key features
IDE
1986
Pre-standard
ATA
1994
PIO modes 0-2, multiword DMA 0
EIDE
ATA-2
1996
16 MB/sec
PIO modes 3-4, multiword DMA modes 1-2, LBAs
ATA-3
1997
SMART
ATA/ATAPI-4
1998
33 MB/sec
Ultra DMA modes 0- 2, CRC, overlap, queuing, 80-wire
Ultra DMA 66
ATA/ATAPI-5
2000
66 MB/sec
Ultra DMA mode 3-4
Ultra DMA 100
ATA/ATAPI-6
2002
100 MB/sec
Ultra DMA mode 5, 48-bit LBA
Ultra DMA 133
ATA/ATAPI-7
2003
133 MB/sec
Ultra DMA mode 6

6. Where ATA Resides in the PC ArchitectureCD HD
SATA

7. Limitations of Parallel ATA
Bandwidth limited to 133 MB/s
Cyclic Redundancy Checking (CRC) for data but not commands
Support attachment of 2 devices per cable
Small switch or jumper for drive selection
High pin count on signaling interface adds cost to cables, connectors and components
Wide cables are cumbersome and inhibit airflow making cooling more difficult and expensive
Connectors hard to insert and remove
Prone to bent pins

8. Benefits of Serial Based Storage
Frame-based transaction protocol (OSI model)
Small, inexpensive connectors and cables
Legacy support - ATA stack in SATA
Ease of integration – cabling, jumpers
Point-to-point connections (expanders, port multipliers)
Pathway to higher data rates; 6 Gb/s is on the roadmap
Improve bandwidth
Wide ports permit several simultaneous connections, allowing for link aggregation (SAS)
Lower cost
Hot-plugable
Enclosure management
Interoperability with SAS
Higher Performance
Ease of integration – cabling, jumpers
Pathway to higher speeds
Legacy support for P-ATA drivers
Lower cost
eSATA; direct storage connect to host (e.g. no USB middleman)

9. PATA and SATA Comparisons
Source: SATA Working Group

10. Native Command Queuing
History of serial ATA
Generation
Standard
Year
Speed
Key features
Serial ATA
ATA/ATAPI-7
2002
150 MB/sec
Serial ATA II
ATA/ATAPI-8
2005
300 MB/sec
Native Command Queuing
Serial ATA III
ATA/ATAPI-9? ?
600 MB/sec

11. SATA Technology Today
SATA has been the most successful recent new storage interface
It has been a multi billion dollar market for several years
In 2006 over 300 million hard disk drives will have SATA interfaces
400 Million Shipped in 2005 (source: Gartner)
Market Leader – Seagate 40% share
SATA has also made its appearance in solid state disks, DVD drives and tape drives
In Desktop, notebooks, Consumer Products - DVR
In the Enterprise! (thanks to STP)
Challenges SAS in the enterprise
Non-critical data
Near-line and offline storage
FC, SAS, and SATA will co-exist offering consumers with a choice of flexible storage options at varying price-points

12. SATA Layer Architecture
August 28, 29, 2006

13. SATA Layer Architecture

14. SATA Layer Architecture

15. SATA Link Layer
August 28, 29, 2006

16. Link Layer – Summary of Functions
Sending/Receiving Frames
8b/10b encoding
Scrambling/Unscrambling
Flow control
CRC calculation

17. Link Layer - 8b/10b Encoding
Data transferred across the link must first be converted from 8-bit values (bytes) into 10 bit values (symbols)
Process is called 8b/10b encoding
Invented by IBM
Also used in the following protocols: Ethernet, Fibre Channel
Purpose for encoding
Clock insertion and recovery
Creates sufficient transition density to limit “Run Length”
DC Balance – main “equal” number of 1’s and 0’s
Ability to encode for special control characters (K)

18. Link Layer - 8b/10b Encoding
Two encodings for each 8-bit value
Dependence on the current running disparity
Two lookup tables are provided for in the specifications

19. Link Layer – Scrambling/Descrambling
SATA frames are scrambled to help with EMI (primitives are not scrambled)
Scrambling occurs before 8b/10b
“Seeding” resets at the detection of a SOF
Descrambled on receive side after the 8b/10b

20. SATA Primitives
Primitives are used as semaphores. They are fixed in content and meaning
Primitive is a dword with one control character followed by 3 data characters
Primitives are used in SATA – the equivalent in Fibre Channel is ordered set
First character is K28.3 (for SATA primitives), or K28.6 (special SATA error primitive)
SATA primitives always send the control character first on the wire
ALIGN K28.5 D10.2 D10.2 D27.3
first
second
third
fourth

21. SATA Primitives SOF D23.1 D23.1 D21.5 K28.3
The Align primitives establish dword boundaries within the serial bit stream. They are sent as data during OOB, and every 2048 dwords there after
Sent First
SOF
D23.1
D23.1
D21.5
K28.3

22. SATA Primitives 18 primitives defined ALIGN CONT R_ERR DMAT R_IP EOF
HOLD
HOLDA
PMACK
PMNAK
PMREQ_P
PMREQ_S
R_ERR
R_IP
R_OK
R_RDY
SOF
SYNC
WTRM
X_RDY

23. SATA Primitives
Primitives are used in a variety of circumstances including:
Indicating intent to send an FIS
Indicating beginning and end of each FIS
Flow Control signaling in response to Transport Layer Buffer state
Reporting Transmission Status

24. Physical Layer
August 28, 29, 2006

25. Physical Layer - Summary
Defines the connectors and cabling used to transmit and receive SATA signaling and data information

26. Physical Layer - SATA Device Connector
Appearance of Serial ATA Connectors
(Drawing courtesy of Molex)
Device connector sizes and locations
Serial
Device plug
connector
2.5"
power
signal
Serial ATA signal connector
(pin S1)
Serial
3.5”
Serial ATA power connector
(pin P1)
power
signal
Legacy Power
(vendor specific)
(5.25” form factor also defined for devices like tape drives and DVDs)
in comparison…
Parallel
3.5”
Host receptacle
connector
parallel ATA signals
4-pin power
Graphics courtesy of the SCSI Trade Association and HP

27. Physical Layer - SATA Cabling
SATA to SATA (1), CO, ST
The most common internal for SATA (and SAS); 1 meter maximum length
SATA Power
To provide legacy power support
eSATA Power (2m)
External SATA; designed for use with external storage products; bypasses the USB route
Graphics courtesy of Molex

28. Phy Layer
August 28, 29, 2006

29. Physical Layer - Summary
OOB (Out of Band) Signaling
Speed Negotiations
Byte/dword synchronization

30. Phy Layer - (OOB) Most primitive level of communication is OOB
They are pattern of idle times and burst times, distinguished by length of time between idles
Idle time (and negation time) are when there are voltage levels
Also known as DC idle
Burst time is during the transmission of the ALIGN primitives
Since byte sync has not occurred yet, the actual bits sent are not relevant – 40 bits will always been detected and consider an ALIGN

31. Phy Layer - (OOB)
COMINIT/COMRESET and COMWAKE are bursts of 6 ALIGN (0) separated by IDLEs
Length of the idle time determines the type of OOB signal
Senders sends 6 – receiver only need to detect 4 (per spec)
COMRESET are sent by hosts
COMINIT are sent by devices
OOB Signal
Idle Time
Negation Time
COMWAKE
55 to 175 ns
> 175 ns
COMINIT/COMRESET
175 to 525 ns
> 525 ns

32. Phy Layer - OOB COMWAKE

33. Phy Layer - OOB COMINIT/COMRESET
Electrically, COMINIT and COMRESET appear exactly the same, the only difference is the direction in which the ALIGN patterns are being sent. Host to device: COMRESET; device to host: COMINIT

34. SATA Power-On Initialization
Starts with the assertion of hardware reset
Begins Out-Of-Band (OOB) signaling
Allows host and device to initialize link communications
Ends with successful transmission of ALIGN primitives
Then speed negotiations

35. Power-On Initialization Process
Host
Device
The register FIS delivers the power-on signature, indicating whether the device is ATA, ATAPI, SEMB, Port Multiplier, etc.

36. SATA Power-On Initialization

37. Error Situation Example: Host and Device are unable to establish a
connection. Continuous transmission errors are seen from
both the Host and Device.
No COMINITs present. Indicates problem with Device connection

38. Primitive Handshaking
Sender
Receiver
X_RDY
R_RDY
SOF
Frame .
EOF
R_IP
WTRM
R_OK

39. Primitive Handshaking
Example: Host sends commands but commands
are not completed
Trace indicates that Host is not properly handling primitive handshaking and is not receiving frames

40. SATA Speed Negotiation
Fast to slow progression
SATA target device sends ALIGN primitives at the fastest supported rate
Waits for host to reply with ALIGNs
If no reply after sending 2048 (i.e., the host doesn’t support this speed), step down to next slower speed and try again

41. SATA Speed Negotiation
When host replies with ALIGNs, it has locked at the current frequency and negotiation is complete
Speed Negotiation

42. Frames
August 28, 29, 2006

43. Frames and the Transport Layer
Frames operate at the Transport Layer
Primitives operate at the Link Layer
Frames convey variable content.
A frame starts with a Start of Frame primitive (SOF).
The frame ends with a CRC dword and an End of Frame primitive (EOF). In between the two primitives are dwords that make up the information content

44. Frames and the Transport Layer
FIS 27 – Used to issue ATA commands to the Device
FIS 46 – Used to transmit Data
FIS 34 – Used by the Device to indicate command completion status
FIS 39 - Used by the device to indicate that it is ready for a DMA transfer
FIS 5F – Used by the device to set up a PIO transfer

45. Example: Transaction is not completed
Frames
Example: Transaction is not completed
Trace indicates invalid CRC. R_ERR indicates receiver detected invalid frame.

46. From PATA to SATA
August 28, 29, 2006

47. PATA to SATA
Task File
In the ATA device
In parallel ATA, accesses to these registers result in parallel ATA traffic
In serial ATA, a Shadow Task file register bank is managed by the host (mirrors the ATA device’s task file)
Allows accesses to these registers to be grouped into larger, more efficient serial transfers

48. PATA to SATA ATA host ATA device PCI bus Parallel ATA Task file
Pass-thru
Task file
IO Reads/Writes
SATA host
SATA device
Serial ATA
Shadow task file
Task file
PCI bus
Frame Information
Structures

49. SATA II
August 28, 29, 2006

50. SATA II
Native Command Queuing
Port Selector
Port Multiplier

51. Native Command Queuing
For multiple outstanding commands in device
Supports reordering of commands (by device! not host)
Supports out-of-order data delivery and re-assembly
SCSI tagged command queuing
Performance of 7200 rpm drive with NCQ is equivalent to that of a standard 10k rpm drive
Less wear-and-tear on drives
Supported through the FPDMA Read Command and FPDMA Write Command
25% Boost In Performance

52. Port Selector SATA typically operates point to point
Port selector permits 1 device to communicate with 2 hosts
Host 1
Link Drive
Host 2

53. Port Multiplier SATA typically operates point to point
Port multiplier feature permits for one SATA link to connect to many devices
Active host with a ratio of 1 host to a maximum of 15 devices – it is acting very much like a hub or repeater
1 to …
Single SATA Link
16 SATA drives

54. Q&A
August 28, 29, 2006

55. Thank You
August 28, 29, 2006