5.3 Global I/O Naming Conventions

Gmn (Gxxx) refers to Global I/Os. These Global I/Os are used to connect the input to global networks. Global networks have high fanout and low skew. The naming convention for Global I/Os is as follows:
  • G = Global
  • m = Global pin location associated with each CCC on the device:
    • A (northwest corner)
    • B (northeast corner)
    • C (east middle)
    • D (southeast corner)
    • E (southwest corner)
    • F (west middle)
  • n = Global input MUX and pin number of the associated Global location m—A0, A1, A2, B0, B1, B2, C0, C1, or C2.

Global (GL) I/Os have access to certain clock conditioning circuitry (and the PLL) and/or have direct access to the global network (spines). Additionally, the global I/Os can be used as regular I/Os, since they have identical capabilities.

Unused GL pins are configured as inputs with pull-up resistors. See more detailed descriptions of global I/O connectivity in the clocking resources chapter of the SmartFusion FPGA Fabric User’s Guide and the clock conditioning circuitry chapter of the SmartFusion Microcontroller Subsystem User’s Guide.

All inputs labeled GC/GF are direct inputs into the quadrant clocks. The inputs to the global network are multiplexed, and only one input can be used as a global input. For example, if GAA0 is used as a quadrant global input, GAA1 and GAA2 are no longer available for input to the quadrant globals. All inputs labeled GC/GF are direct inputs into the chip-level globals, and the rest are connected to the quadrant globals.