Each of the 24 BUFGCE/MBUFGCE buffers in an XPIO clock region can only drive a specific clock routing track. However, the BUFGCTRL/MBUFGCTRL and BUFGCE_DIV/MBUFGCE_DIV outputs can use any of the 24 tracks by going through a MUX structure. Each BUFGCE_DIV/MBUFGCE_DIV shares the input connectivity with a specific BUFGCE site, and each BUFGCTRL/MBUFGCTRL shares input connectivity with two specific BUFGCE sites. Consequently, when BUFGCE_DIV/MBUFGCE_DIV or BUFGCTRL/MBUFGCTRL buffers are used in the clock region, use of the BUFGCE/MBUFGCE buffers is limited. The following figure shows the bottom 6 BUFGCE sites in a clock region, which are replicated 4 times within an XPIO clock region.
Note: A global clock net is assigned to a
specific track ID in the device for all the vertical, horizontal routing, and
distribution resources the clock uses. A clock cannot change track IDs unless the clock goes through another clock
buffer.
Figure 1. BUFGCE, BUFGCE_DIV, and BUFGCTRL Shared Inputs and Output
Multiplexing
Note: BUFG* sites with X6Y# denote the XPIO CLOCK_REGION X6Y0.