BUFGSR

Global Set/Reset Input Buffer

BUFGSR, an XC9000-specific global buffer, distributes global set/reset signals throughout selected flip-flops of an XC9000 device. Global Set/Reset (GSR) control pins are available on XC9000 devices; consult device data sheets for availability.

BUFGSR always acts as an input buffer. To use it in a schematic, connect the input of the BUFGSR symbol to an IPAD or an IOPAD representing the GSR signal source. GSR signals generated on-chip must be passed through an OBUF-type buffer before they are connected to BUFGSR.

For global set/reset control, the output of BUFGSR normally connects to the CLR or PRE input of a flip-flop symbol, like FDCP, or any registered symbol with asynchronous clear or preset. The global set/reset control signal may pass through an inverter to perform an active-low set/reset. The output of BUFGSR may also be used as an ordinary input signal to other logic elsewhere in the design. Each BUFGSR can control any number of flip-flops in a design.