北京航空航天出版社
2.7ExplainwhyNANDandNORgatesaremorecommonthanANDandORgates.
BecausepMOStransistorsdon'tconductzerosverywellandnMOStransistorsdon'tconductonesverywell,ANDandORgatesaredesignedbyusingNANDandNORgates,respectively,alongwithaninvertor.Thus,NANDandNORgatesaremorecommonduetotheirreducedsize.
2.8Distinguishbetweenacombinationalcircuitandasequentialcircuit.
Acombinationalcircuitisadigitalcircuitwhoseoutputispurelyafunctionofitspresentinputs.Asequentialcircuitisadigitalcircuitwhoseoutputsareafunctionofthepresentaswellasthepreviousinputvalues.
2.9Designa2-bitcomparator(comparestwo2-bitwords)withasingleoutput“less-than,”
usingthecombinationaldesigntechniquedescribedinthechapter.Startfromatruthtable,useK-mapstominimizelogic,anddrawthefinalcircuit.a1
1
1
1
1
1
1
1
1a00000111100001111b10011001100110011b0010101010
1010101lt(a<b)0111001100010000aab1blt=b1a1'+b0a1'a0'+b1b0a0'a1a0b1b0lt
EmbeddedSystemDesign17