本答复记录主要讨论均衡及裕量的调试。
注意：本答复记录是 Xilinx HSSIO 解决方案中心的一部分（Xilinx 答复 37181）。
The HSSIO Solution Center is available to address all questions related to HSSIO.
无论您是要启动新设计还是要调试问题，请访问HSSIO 解决方案中心来指导您获取相应的信息。
For 7 Series and UltraScale/UltraScale+ devices, the equalization varies widely depending on the application and board layout.必须根据信道设计，特别是奈奎斯特频率下的信道损耗，选择均衡设置。
问题通常是由于保留向导选择的默认设置（不根据预期的设计调整设置）引起的。The wizard chooses optimized attributes based on the insertion loss and RxEQ (Auto vs LPM vs DFE) settings in the GUI, so these must reflect the real system.The RxEQ = Auto option chooses equalization based on insertion loss setting.Read back the RXLPMEN port value to confirm the equalizer type.
For low loss short channels, typically using LPM, low TX amplitude and no de-emphasis behaves better.
When using DFE, the auto adaptation requires incoming data to be random, so carefully consider if data is 8B10B or if there is no data scrambling.See the LPM vs DFE section in the Transceiver User Guides.
从理论上讲，没有一个信道没有误差，所以要选择均衡设置，就要选择一个目标误码率 (BER)。
查看（Xilinx 答复 57449）— 误码率 101。
The IBIS-AMI model used with some of the available Signal Integrity tools (such as ADS) will model the internal equalization and give an estimate of the BER that a given channel can achieve.
Use the eye scan mask included in the IBIS-AMI model User Guides to evaluate link margin.
The model can also be used to optimize the TX/RX equalization settings.
Transmitter amplitude and de-emphasis can be tuned through TXDIFFCTRL, TXPRECURSOR, and TXPOSTCURSOR.The entire TX parameter space can be evaluated through parameter sweep.Try a coarse sweep followed by fine tuning.TXPRECURSOR and TXPOSTCURSOR values can start with 3dB increments during the sweep.
Carefully set the simulation-specific parameters to guarantee accurate simulation results.The included IBIS-AMI model user guide provides instructions on how to set the parameters according to the design target, for example, line rate and insertion loss.The parameters should be chosen based on the settings used in the GT wizard GUI.Select the RX equalizer between LPM and DFE using RXLPMEN.In general, RX performs well with the default auto adaptation so no further RX tuning should be needed.Observe the adaptation loop values in the output csv files to make sure that no loop is misbehaving.
TX_PVT and RX_PVT parameters cover the extreme worst cases of the hardware.All 3 corners should be simulated to evaluate overall link margin.The TX die termination model has dedicated corner models for each TT/FF/SS corner, and the corresponding TX die termination model must be used in conjunction with the same TX_PVT corner.There is little corner variation observed on hardware for RX die termination so only one RX die termination model is provided for simulations over all 3 corners.
For *.ibs, use the typical corner for all simulations.Generally *.ibs files are used to model the analog front end of the silicon (on-die).Instead of using the settings provided in the *.ibs files, we use our on-die s-parameter models, which is a better representation.
查看串行链路信号分析白皮书 (WP428)：
//m.akhomesold.com/support/documentation/white_papers/wp428-7Series-Serial-Link-Signal-Analysis.pdf
用于裕量分析的两款主要硬件工具是 IBERT 和眼扫描。
In UltraScale/UltraScale+ devices you have the In System IBERT built into the GT wizard, that can deliver on-the-fly Eye Scan results using system data.
The in-system IBERT will be automatically included in the generated example design.Run eye scans through Serial I/O Analyzer in the hardware manager.
Eye Scan analysis can also be designed into a system to measure the data eye on the fly which can save a lot of debug time.
See the manual eye scan instructions answer records for the GT in use:
不要把 TX 方面排除在优化进程之外。
优化发送端的重要组件（前置和后置），通常是获得预期结果所需要的全部，有时它只是可以修复一个无力 TX 通道的调整。