The Power Delivery Network is what provides power for all the macros in your design.
For the shuttle, OpenLANE creates a PDN that supplies the 4 rails available to the user project area:
inout vdda1, // User area 1 3.3V supply
inout vdda2, // User area 2 3.3V supply
inout vssa1, // User area 1 analog ground
inout vssa2, // User area 2 analog ground
inout vccd1, // User area 1 1.8V supply
inout vccd2, // User area 2 1.8v supply
inout vssd1, // User area 1 digital ground
inout vssd2, // User area 2 digital ground
Metal 4 is used for vertical lines that are cut for the macros, and Metal 5 routes over the top of everything.
When the metal 5 lines pass over the macro, vias are dropped to connect the macro’s internal PDN to the user project area’s PDN.