ModuleWare Reference Guide - Hornad

Combinatorial PartsDecoder, Separate Outputs (decoder)Decoder, Separate Outputs (decoder)This part decodes the log2(N)-bit input port din and places the result inseparate scalar output ports dout0 to doutN.The default part has two outputs dout0 and dout1 and is equivalent to oneNOT gate. However, you can resize the component instance to implementparts with four, eight (or any other multiple of two) output ports.A four-output decoder is equivalent to four 2-bit AND gates and up to fourNOT gates.An eight-output decoder is equivalent to eight 3-bit AND gates and up totwelve NOT gates.The HDL code for any unused ports is optimized away.The same functionality is also provided by the Decoder, Combined Output(decoder1) part using a single output bus.FunctionThe default two-output decoder has the following function:dout0dout1= NOT(din)= dinA four-output decoder has the following function:dout0dout1dout2dout3= (NOT(din(1))) AND (NOT(din(0)))= (NOT(din(1))) AND din(0)= din(1) AND (NOT(din(0)))= din(1) AND din(0)An eight-output decoder has the following function:dout0dout1dout2dout3dout4dout5dout6dout7= (NOT(din(2))) AND (NOT(din(1))) AND (NOT(din(0)))= (NOT(din(2))) AND (NOT(din(1))) AND din(0)= (NOT(din(2))) AND din(1) AND (NOT(din(0)))= (NOT(din(2))) AND din(1) AND din(0)= din(2) AND (NOT(din(1))) AND (NOT(din(0)))= din(2) AND (NOT(din(1))) AND din(0)= din(2) AND din(1) AND (NOT(din(0)))= din(2) AND din(1) AND din(0)64ModuleWare Reference Manual, Library Version 1.9September 18, 2008