Intel® Quartus® Prime Standard Edition User Guide: Design Recommendations

ID 683323
Date 9/24/2018
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2.6.5.2.1. Binary Multiplexers

Binary multiplexers select inputs based on binary-encoded selection bits.

Device families featuring 6-input look up tables (LUTs) are perfectly suited for 4:1 multiplexer building blocks (4 data and 2 select inputs). The extended input mode facilitates implementing 8:1 blocks, and the fractured mode handles residual 2:1 multiplexer pairs.

For device families using 4-input LUTs, such as the Cyclone®  series and Stratix® series devices, Intel® Quartus® Prime implements the 4:1 binary multiplexer efficiently by using two 4-input LUTs. Intel® Quartus® Prime decomposes larger binary multiplexers into 4:1 multiplexer blocks, possibly with a residual 2:1 multiplexer at the head.

Verilog HDL Binary-Encoded Multiplexers

case (sel)
   2'b00: z = a;
   2'b01: z = b;
   2'b10: z = c;
   2'b11: z = d;
endcase