Global Clock Inputs

UltraScale Architecture Clocking Resources User Guide (UG572)

Document ID
Release Date
1.10.2 English

External global user clocks must be brought into the UltraScale device on differential clock pin pairs called global clock (GC) inputs. There are four GC pin pairs in each bank that have direct access to the global clock buffers, MMCMs, and PLLs that are in the CMT adjacent to the same I/O bank. The UltraScale+ architecture has four HDGC pins per HD I/O bank. HD I/O banks are only part of the UltraScale+ family. Since HD I/O banks do not have a XIPHY and CMT next to them, the HDGC pins can only directly drive BUFGCEs (BUFGs) and not MMCMs/PLLs. Therefore, clocks that are connected to an HDGC pin can only connect to MMCMs/PLLs through the BUFGCEs. To avoid a design rule check (DRC) error, set the property CLOCK_DEDICATED_ROUTE = FALSE. GC inputs provide dedicated, high-speed access to the internal global and regional clock resources. GC inputs use dedicated routing and must be used for clock inputs where the timing of various clocking features is imperative. General-purpose I/O with local interconnects should not be used for clock signals.

Each I/O bank is located in a single clock region and includes 52 I/O pins. Of the 52 I/O pins in each I/O bank in every I/O column, there are four global clock input pin pairs (a total of eight pins). Each global clock input:

Can be connected to a differential or single-ended clock on the PCB.

Can be configured for any I/O standard, including differential I/O standards.

Has a P-side (master), and an N-side (slave).

Single-ended clock inputs must be assigned to the P (master) side of the GC input pin pair. If a single-ended clock is connected to the P-side of a differential clock pin pair, the N-side cannot be used as another single-ended clock pin—it can only be used as a user I/O. For pin naming conventions, refer to the UltraScale Architecture Packaging and Pinout User Guide (UG575) [Ref 2] .

GC inputs can be used as regular I/O if not used as clocks. When used as regular I/O, global clock input pins can be configured as any single-ended or differential I/O standard. GC inputs can connect to the PHY adjacent to the banks they reside in.