BUFGLS

Global Low Skew Clock Buffer

Each corner of the XC4000X or SpartanXL device has two Global Low-Skew buffers (BUFGLS). Any of the eight buffers can drive any of the eight vertical global lines in a column of CLBs. In addition, any of the buffers can drive any of the four vertical lines accessing the IOBs on the left edge of the device and any of the eight vertical lines accessing the IOBs on the right edge of the device.

IOBs at the top and bottom edges of the device are accessed through the vertical global lines in the CLB array. Any global low-skew buffer can, therefore, access every IOB and CLB in the device.

The global low-skew buffers can be driven by either semi-dedicated pads or internal logic.