UNH Inter Operability Lab Serial Attached SCSI SAS
UNH Inter. Operability Lab Serial Attached SCSI (SAS) Clause 5 Considerations Improving Networks Worldwide.
Improving Networks Worldwide.
SAS Clause 5 Considerations Presentation Topics • Transmission Speeds and Unit Intervals • OOB Construction • Differential Signaling 3
SAS Clause 5 Considerations Physical Link Rate (Nominal) • 1. 5 Gbps SAS – 150 MBps (Mega. Bytes Per Second) • 3. 0 Gbps SAS – 300 MBps • 6. 0 Gbps SAS – 600 MBps 4
SAS Clause 5 Considerations Unit Intervals (Nominal) • 1. 5 Gbps SAS – 66666 ps (picoseconds) = 2000/3 ps • 3. 0 Gbps SAS – 33333 ps = 1000/3 ps • 6. 0 Gbps SAS – 166. 66666 ps = 500/3 ps 5
SAS Clause 5 Considerations Baud Rate (Nominal) • 1. 5 Gbps SAS – 1. 5 Gigasymbols/s • 3. 0 Gbps SAS – 3. 0 Gigasymbols/s • 6. 0 Gbps SAS – 6. 0 Gigasymbols/s 6
SAS Clause 5 Considerations OOB Signal Construction • Out-Of-Band Signals • Consists of Bursts Dwords and Gaps of DC Idle • Built with D 24. 3 characters – 110011 – 001100 7
SAS Clause 5 Considerations OOB Interval • Minimum – 665. 06666 ps = 66666 x (1 – 0. 0024) • Nominal – 66666 ps • Maximum – 668. 26666 ps = 66666 x (1 + 0. 0024) • 1 OOBI = 66666 ps (Nominal) 8
SAS Clause 5 Considerations OOB Signals • Built from three parts: – Bursts, Idles, Negations • Three different signals – COMWAKE – COMINIT/COMRESET – COMSAS 9
SAS Clause 5 Considerations COMWAKE • SATA Signal • Special use for new features in SAS-2 • Burst Time – 160 OOBI (106. 66666 ns) • Idle Time – 160 OOBI (106. 66666 ns) • Negation Time – 280 OOBI (186. 66666 ns) • Total Signal Time – 2200 OOBI (1466. 6666 ns) 10
SAS Clause 5 Considerations COMWAKE 160 OOBI Each Total Time: 2200 OOBI 280 OOBI 160 OOBI Each 11
SAS Clause 5 Considerations COMINIT/COMRESET • SATA and SAS Signal • Used to Initialize and Reset the entire connection • Burst Time – 160 OOBI (106. 66666 ns) • Idle Time – 480 OOBI (320 ns) • Negation Time – 800 OOBI (533. 33333 ns) • Total Signal Time – 4640 OOBI (3093. 3333 ns) 12
SAS Clause 5 Considerations COMINIT/COMRESET 160 OOBI Each 480 OOBI Each 800 OOBI Total Time: 4640 OOBI 13
SAS Clause 5 Considerations COMSAS • SAS Only Signal • Used to communicate that a device is a SAS device • Burst Time – 160 OOBI (106. 66666 ns) • Idle Time – 1440 OOBI (960 ns) • Negation Time – 2400 OOBI (1600 ns) • Total Signal Time – 12000 OOBI (8000 ns) 14
SAS Clause 5 Considerations COMSAS 160 OOBI Each 2400 OOBI 1440 OOBI Each Total Time: 12000 OOBI 15
SAS Clause 5 Considerations Detecting OOB Signals • Signals are detected via Idle times NOT Burst times • Burst Tolerances – MAY detect all any burst <= 100 ns – SHALL detect all bursts > 100 ns 16
SAS Clause 5 Considerations Idle Time Detection Requirements • COMWAKE – MAY Detect • 35 ns <= Tidle < 175 ns – SHALL Detect • 101. 3 ns <= Tidle <= 112 ns – SHALL NOT Detect • Tidle < 35 ns • Tidle >= 175 ns 17
SAS Clause 5 Considerations Idle Time Detection Requirements • COMINIT/COMRESET – MAY Detect • 175 ns <= Tidle < 525 ns – SHALL Detect • 304 ns <= Tidle <= 336 ns – SHALL NOT Detect • Tidle < 175 ns • Tidle >= 525 ns 18
SAS Clause 5 Considerations Idle Time Detection Requirements • COMSAS – MAY Detect • 525 ns <= Tidle < 1575 ns – SHALL Detect • 911. 7 ns <= Tidle <= 1008 ns – SHALL NOT Detect • Tidle < 525 ns • Tidle >= 1575 ns 19
SAS Clause 5 Considerations Differential Signaling • Used to aid in handling noise on the line • One + signal and one – signal transmitting in each direction 20
SAS Clause 5 Considerations Differential Signaling 21
SAS Clause 5 Considerations Differential Signaling • Negative Signal is subtracted from the positive signal at the receiver 22
SAS Clause 5 Considerations Differential Signaling • Result – Because ‘opposite’ signals were transmitted initially; output signal is twice as powerful – Noise will, theoretically, be applied equally to both channels of the differential signal; noise is eliminated from the output signal 23
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