Agilex™ 7 LVDS SERDES User Guide: F-Series and I-Series
                    
                        ID
                        721819
                    
                
                
                    Date
                    9/05/2024
                
                
                    Public
                
            
                
                    
                        1. Agilex™ 7 F-Series and I-Series LVDS SERDES Overview
                    
                    
                
                    
                        2. Agilex™ 7 F-Series and I-Series LVDS SERDES Architecture
                    
                    
                
                    
                        3. Agilex™ 7 F-Series and I-Series LVDS SERDES Transmitter
                    
                    
                
                    
                        4. Agilex™ 7 F-Series and I-Series LVDS SERDES Receiver
                    
                    
                
                    
                        5. Agilex™ 7 F-Series and I-Series High-Speed LVDS I/O Implementation Guide
                    
                    
                
                    
                        6. Agilex™ 7 F-Series and I-Series LVDS SERDES Timing
                    
                    
                
                    
                        7. LVDS SERDES Intel® FPGA IP Design Examples
                    
                    
                
                    
                        8. Agilex™ 7 F-Series and I-Series LVDS SERDES Design Guidelines
                    
                    
                
                    
                    
                        9. Agilex™ 7 F-Series and I-Series LVDS SERDES Troubleshooting Guidelines
                    
                
                    
                    
                        10. Documentation Related to the Agilex™ 7 LVDS SERDES User Guide: F-Series and I-Series
                    
                
                    
                    
                        11. Document Revision History for the Agilex™ 7 LVDS SERDES User Guide: F-Series and I-Series
                    
                
            
        6.2.2. Receiver Skew Margin
 Different modes of SERDES receivers use different specifications, which determine the ability to sample the received serial data correctly. 
  
 
  - In the non-DPA mode, use RSKM, TCCS, and sampling window (SW) specifications for high-speed source-synchronous differential signals in the receiver data path.
 - In the DPA and Soft-CDR modes, use DPA jitter tolerance instead of the receiver skew margin (RSKM).
 
   Equation 2. RSKM EquationThis equation expresses the relationship between RSKM, TCCS, and SW.
    
     
  
 
  
| Symbol | Description | 
|---|---|
| RSKM | The timing margin between the clock input of the receiver and the data input sampling window, and the jitter induced from core noise and I/O switching noise. | 
| Time unit interval (TUI) | The time period of the serial data. | 
| SW | The period of time that the input data must be stable to ensure that the LVDS SERDES receiver samples the data successfully. The SW is a device property and varies according to device speed grade. | 
| TCCS | The timing difference between the fastest and the slowest output edges across channels driven by the same PLL. The TCCS measurement includes the tCO variation, clock, and clock skew. | 
   Note: If there is additional board channel-to-channel skew, consider the total receiver channel-to-channel skew (RCCS) instead of TCCS.   . 
  
 
  You must calculate the RSKM value, based on the data rate and device, to determine if the LVDS SERDES receiver can sample the data:
- A positive RSKM value, after deducting transmitter jitter, indicates that the LVDS SERDES receiver can sample the data properly.
 - A negative RSKM value, after deducting transmitter jitter, indicates that the LVDS SERDES receiver cannot sample the data properly.
 
    Figure 30. Differential High-Speed Timing Diagram and Timing Budget
     
      
   
 
  RSKM Calculation Example
This example shows the RSKM calculation for F-Series and I-Series devices at 1 Gbps data rate with a 200 ps board channel-to-channel skew.
    Equation 3. RSKM Calculation
     
      
   
 
   
The non-DPA receiver works correctly if the RSKM is greater than 0 ps after deducting transmitter jitter.