I n Chapter 1 we said that several types of integrated circuit chips are available for imple-…

 

In Chapter 1 we said that several types of integrated circuit chips are available for imple- mentation of logic circuits, and that field-programmable gate arrays (FPGAs) are commonly used. In an FPGA, logic functions are not implemented directly using AND, OR, and NOT gates. Instead, an FPGA implements logic functions by using a type of circuit element called lookup tables (LUTs). A LUT can be programmed by the user to implement any logic function of its inputs. Thus, if a LUT has three inputs, then it can implement any logic function of these three inputs. We describe FPGAs and lookup tables in detail in Appendix B. Consider the four-input function

f  = x1x2x4 + x2x3x4 + x1x2x3

Show how this function can be implemented in an FPGA that has three-input LUTs.