DS90UB954-Q1:Question for Margin analysis setup

Hello,

Thank you for your questions.

1. The base delay selection is used to enable and disable the base delay of the devices. When selected/checked the register STROBE_SET[7] and STROBE_SET[3] will be set to 1. This corresponds to a base delay of 0. By default the base selection is not selected, which corresponds to a base delay of 6. Both of these results are valid for each respective register setting. You can program either option via the registers, so as long as you refer to the results that corresponds to the register setting that will be used in your system during operation there will not be a problem.
   
   
2. Do you mean how to determine appropriate values to set as the min/max values? It is recommended to leave the max EQ level at 14 to account for potential aging degradation. The min EQ value can be chosen as the lowest EQ level that contains at least 4 valid strobe positions. Looking at the results you provided, EQ 0 would be the lowest level so an appropriate range would be EQ 0 as the minimum and EQ 14 as the maximum. The strobe positions should be chosen in a way so that each EQ level has at least 4 valid strobe positions. Looking at the results, an appropriate range would be position 6 to position 11.
   
   
3. The dwell time is the amount of time that passes before lock and errors are checked for a given AEQ setting. A larger dwell time can provide more confidence in the results as each setting will be evaluated for a longer period of time. The default dwell time is 1 second and is acceptable for most systems. You can choose the dwell time based on how long you would like the MAP analysis to complete and how much confidence is desired in the results. 
4. The EQ is the equalizer value setting. The goal of the Adaptive Equalizer (AEQ) process is to step through all the different EQ settings/levels to find a value that allows for a stable lock.

Regards,
Darrah

Hello,

1. Yes, your understanding is correct.

2. The devices normally select the EQ and strobe position through the adaption mode, where each EQ and strobe position will be looped through until a valid lock is found. The benefit of choosing a min and max value is that this adaption loop can be configured to be slightly smaller and focus only on the settings that have the best chance of stable lock. It is recommended to set the EQ max no lower than 14. Even though this would include some of the red area, this is done because as cables degrade with age, the higher EQ levels may become more effective. You can choose the min and max of the strobe positions to make the range as large as desired, the only recommendations is to ensure that there are at least 4 valid strobes for the majority of EQ levels. This means for some EQ levels there may be less than 4 valid strobe positions, this is okay as long as the majority of EQ levels have 4 valid strobes. Since the devices will still loop through each EQ and strobe position until a valid lock is found, it is okay if some non-valid settings are included in the min and max range.

3. Based on result 1, EQ 0 to14 and SP 6 to 11 would be appropriate.

Hello,

The AEQ registers don't clear automatically, so the min and max values programmed at initialization will remain unless they are overwritten/reset. If the devices lose lock, the AEQ will resume incrementing at the current AEQ setting and will automatically find another valid lock based on the register configurations.

Hello,

The adaptive equalization process used to find a valid lock is the same at initial start up and during operation if lock is lost.

1. Yes, the loop will repeat until a valid lock is found.

2. The time to find another valid lock will depend greatly on the condition of the system. Each setting is evaluated for a default dwell time of 2.62ms before incrementing to the next setting. The dwell time can be configured in register 0xD2. The total time to find another valid lock will depend on how many settings the process loops through before finding a valid lock.

3. If the devices don't have lock, they will not be able to communicate with each other. This means there will be no data or communication exchanged across the FPD-link channel. However, local I2C transactions to the DS90UB954-Q1 would still be possible.

4. You can determine if there is a stable lock from the status pin or register 0x4D.

5. The current EQ level can be read from register 0xD3 and the current strobe position can be read using registers 0xD6 and 0xD7.