ModuleWare Reference Guide - Hornad

Decoder, Combined Output (decoder1)Combinatorial PartsDecoder, Combined Output (decoder1)This part decodes the input port din and places the result on output portdout.Because the widths of din and dout are both user-definable, an optionalscalar output port selerror can be used to flag an unsuccessful decodeoperation. Let n be the width of din and m be the width of dout.Ifm >=2**n the decoded result is guaranteed to fit into dout so selerror is setto 0.If however, m = width of port doutif the decoded value of port din < width of port doutTruth TableFor every bit i of the bus:dout(i) = if (i == din) then 1 else 03 to 8-bit example:Table 4-5. Decoder Truth Table — Combined Outputdindout000 00000001001 00000010010 00000100011 00001000100 00010000ModuleWare Reference Manual, Library Version 1.9 67September 18, 2008