SAS-3 Transmitter Training Review Harvey Newman April 14, 2011 T10/11-164r2

SAS proposal for control register proposed in 10-025r0 Index Name Values 15 Reset 1 = Reset coefficients to the no equalization state (e.g. ci=0 for i ≠ D) 0 = Normal operation 14:6 Reserved Write as zero, ignore on read 5:4 Coefficient (+1) update request 5 4 1 1 = Reserved 1 0 = Decrement 0 1 = Increment 0 0 = Hold 3:2 Coefficient (0) update request Encoding per coefficient (+1) update request 1:0 Coefficient (-1) update request T10/11-164r2

Revised Proposal for SAS Control Register 11-044r0 Index Name Values 15:14 Coefficient settings 11b = Reserved 10b = Default coefficients (set by manufacturer) 01b = Set Tx to a specified operating condition to be determined by the phy committee (Reference) (Not persistent across reset, reference Tx mode for characterization) 00b = Normal operation (up to Tx to determine, may use default or last know value) 13:6 Reserved Write as zero, ignore on read 5:4 Coefficient (+1) update request 5 4 1 1 = Reserved 1 0 = Decrement 0 1 = Increment 0 0 = Hold 3:2 Coefficient (0) update request Encoding per coefficient (+1) update request 1:0 Coefficient (-1) update request T10/11-164r2

Revised Proposal for SAS Control Register 11-036r2 Index Name Values 15:13 Pattern Type All others = Reserved 000b = Normal operation (up to Tx to determine, may use default or last know value) 12 Reserved Write as zero, ignore on read 11-10 Coefficient Settings 11b = Reserved 10b = Default coefficients (set by manufacturer) 01b = Set Tx to a specified operating condition to be determined by the phy committee (Reference) 00b = Normal operation (up to Tx to determine, may use default or last know value) 9:6 5:4 Coefficient (+1) update request 5 4 1 1 = Reserved 1 0 = Decrement 0 1 = Increment 0 0 = Hold 3:2 Coefficient (0) update request Encoding per coefficient (+1) update request 1:0 Coefficient (-1) update request T10/11-164r2

Coefficient Update Proposed in 10-025r0 Coefficient Update Proposed in 10-025r0. Dashed Line Represents Waveform Before Update. V3(k) V1(k-1) V1(k) V3(k) V1(k-1) V3(k-1) V3(k-1) V1(k-1) V2(k) V2(k-1) V2(k) V1(k) V2(k-1) V1(k) V2(k-1) V3(k-1) V1(k-1) V2(k-1) V3(k) V2(k) V3(k) V1(k) V3(k-1) V2(k) C(-1) Increment C(1) Increment C(1) Decrement C(-1) Decrement V1(k) V3(k) V1(k-1) V3(k-1) V2(k) V2(k-1) V1(k-1) V2(k-1) V3(k-1) V1(k) V2(k) V3(k) C(0) Increment C(0) Decrement Cpost Cctr Cpre T10/11-164r2

Maxim Commands Summary 11-049r3 All green commands are 2dV T10/11-164r2

Maxim Proposed Commands 11-049r3 All green commands are 1dV. They should be twice as large because two steps are being applied. T10/11-164r2

Eleven commands with adjusted numbers to match original proposal. T10/11-164r2

What do we what to specify? Maximum amplitude at the Transmitter connector 1200mVppd This provides a maximum Voltage limit for future generations. Minimum amount of equalization available from the transmitter Receivers will not have the ability to fully equalize the worst case channel without some help from the transmitter. Monotinicity for transmitter adjustment. In order to allow the control loop in the receiver to converge to an optimal equalizer setting when it tells the transmitter to increase equalization, the transmitter shall not decrease equalization. This is why the transmitter minimum step size is a value greater than zero. Maximum stress caused by a compliant TxRxConnection The amount of total system equalization has to be specified greater than the worst case compliant TxRxConnection. Some of the equalization will be at the transmitter and some at the receiver. Starting point for equalization search. T10/11-164r2

What do we not want to specify? Implementation We want to allow transmitters to be either voltage mode or current mode drivers. We want to allow receivers to apply a variety of different types of equalization and even combinations of multiple types. Linear (boost high frequency, works best for smooth channels) DFE (works best for “bumpy” channels and does not amplify crosstalk) Algorithms There will be multiple different ways to search for an optimal system equalization Parameters within the control of a single deliverable Signal wave shape at the die is not of interest for compliance when the package and remaining interconnect out to the SAS compliance point is part of the transmitter device. Preset values based on worst case channel analysis The worst case channels represent a small percentage of the overall implementations. T10/11-164r2

This implies adjusting Cpre 5 times has no change in the Cpost This implies adjusting Cpre 5 times has no change in the Cpost. See next slide. T10/11-164r2

Adjusting Either Pre or Post Interacts with the Other Adjusting Either Pre or Post Interacts with the Other. Note: 10mV steps are the smallest allowed when two steps are taken together. Allowing Cpre or Cpost adjustment without tying it to Cctr provides twice the resolution for our equalization without increasing the number of dimensions in the search. T10/11-164r2

Why provide an example with 100mV VMA? The maximum amplitude is 1200mV, this leads to an operating voltage around 1000mV The worst case channels we have been looking at have in the order of 20dB signal attenuation at Nyquist. This reduces the high frequency components from 1000mV to 100mV Note 20dB is a ratio of 1/10th To equalize the system we want to have the high frequency and low frequency signal energy nearly the same. Receivers sample signals on the order of 100mV after signal conditioning. If crosstalk is significant then reducing transmitted signal amplitude is more beneficial than attenuating the signal inside the receiver. We need to allow the receiver to adjust for optimal system performance. T10/11-164r2

Insertion loss Vs. NEXT from 10-025r0 T10/10-025r0

Amplitude Changes Equalization Once there is equalization an amplitude change causes a change in the equalization applied. If we equalize then adjust C0 you have changed the amount of equalization. After the change you want to only adjust equalization. We would like to minimize the interaction between adjustments. Constant swing commands cause an interaction between Pre and Post T10/11-164r2

Constant Swing Adjustments Following an Amplitude Change T10/11-164r2

T10/11-164r2

Maxim proposal for compliance point from 11-049r3 T10/11-164r2

Connector Compliance Point Preferred Over Virtual Point Virtual compliance points complicate measurement and interoperability Limits maximum signal swing before a known amount of loss T10/11-164r2

LSI Proprietary