Arria V Avalon-ST Interface for PCIe Solutions User Guide
B. Lane Initialization and Reversal
Connected components that include IP blocks for PCI Express need not support the same number of lanes. The ×4 variations support initialization and operation with components that have 1, 2, or 4 lanes. The ×8 variant supports initialization and operation with components that have 1, 2, 4, or 8 lanes.
Lane reversal permits the logical reversal of lane numbers for the ×1, ×2, ×4, and ×8 configurations. Lane reversal allows more flexibility in board layout, reducing the number of signals that must cross over each other when routing the PCB.
|   Lane Number  |  
        7  |  
        6  |  
        5  |  
        4  |  
        3  |  
        2  |  
        1  |  
        0  |  
     
|---|---|---|---|---|---|---|---|---|
|   ×8 IP core  |  
        7  |  
        6  |  
        5  |  
        4  |  
        3  |  
        2  |  
        1  |  
        0  |  
     
|   ×4 IP core  |  
        —  |  
        —  |  
        —  |  
        —  |  
        3  |  
        2  |  
        1  |  
        0  |  
     
| — | — | — | — | — | — | — | 1 | 0 | 
|   ×1 IP core  |  
        —  |  
        —  |  
        —  |  
        —  |  
        —  |  
        —  |  
        —  |  
        0  |  
     
|   Core Config  |  
        8  |  
        4  |  
        1  |  
     |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
|   Slot Size  |  
        8  |  
        4  |  
        2  |  
        1  |  
        8  |  
        4  |  
        2  |  
        1  |  
        8  |  
        4  |  
        2  |  
        1  |  
     
|   Lane pairings  |  
        7:0,6:1,5:2, 4:3, 3:4,2:5, 1:6,0:7  |  
        3:4,2:5, 1:6,0:7  |  
        1:6, 0:7  |  
        0:7  |  
        7:0,6:1, 5:2,4:3  |  
        3:0,2:1, 1:2,0:3  |  
        3:0, 2:1  |  
        3:0  |  
        7:0  |  
        3:0  |  
        1:0  |  
        0:0  |