LUT_OUTPUTbuffer specifies a LUT function. The
LUT_OUTPUTbuffer works like a hard
LCELLbuffer with the additional detail of specifying the inputs and without the requirement that the LUT function will become a hard output. The
LUT_INPUTbuffer marks input signals for a
LUT_OUTPUTbuffer. The logical functionality of the
LUT_INPUTbuffers is a simple wire, but together they identify LUT boundaries.
To make a LUT, you need to use both input and output buffers that bound a cone of logic, as in the following example.
FUNCTION lut_output (in) RETURNS (out); FUNCTION lut_input (in) RETURNS (out); SUBDESIGN test ( ina : INPUT ; inb : INPUT ; inc : INPUT ; ind : INPUT ; outd : OUTPUT ; ) BEGIN outd = lut_output( lut_input (ina) & lut_input (inb) & lut_input (inc) & lut_input (ind) ) ; END ;
Note: For information about Quartus® Prime primitive instantiation, go to Using a Quartus® Prime Logic Function.