数字逻辑设计及应用教学课件：answer key for CHAPTER 8-

1、CHAPTER 8Answer Key8-13(P719)The counting direction is controlled by QD: count up when QD=1, count down when QD=0. A load occurs when the counter is in the terminal state, 1111 when counting up, 0000 when counting down. The MSB is complemented during a load and the other bits are unchanged.8-13(P719

2、)Let us assume that the counter is initially in one of the states 00000111. Then the counter counts down(QD=0). Upon reaching state 0000, it loads 1000 and subsequently counts up (QD=1). Upon reaching state 1111, the counter loads 0111, and subsequently counts down, repeating the cycle.8-13(P719)If

3、the counter is initially in one of the states 10001111, the same cyclic behavior is observed. The counting sequence has a period of 16 and is, in decimal,8, 9, 10, 11, 12, 13, 14, 15, 7, 6, 5, 4, 3, 2, 1, 0, 8, 9, .8-14 CLKCLRLDENPENTA QAB QBC QCD QD RCO74x163(QA QC)+5VCLOCK0001(QB QD)QDQCQBQALD_L=(

4、QAQC)CLR_L=(QBQD)description000011COUNT000111COUNT001011COUNT001111COUNT010011COUNT010101LOAD100011COUNT100111COUNT101010CLEAR000011COUNT000011COUNT000111COUNT001011COUNT001111COUNT010011COUNT8.354,5,6-13,14,4,5,6Load 0100 when 1414=1110(2)So ld_l=?Ld_l=(QDQCQB)DCBA=01008.384,5,6-13,14,4,5,6Load 010

5、0 when 1414=1110(2)So ld_l=?Ld_l=(QDQCQB)DCBA=01008.380-12810 = ( 10000000 )2 CLKCLRLDENPENTA QAB QBC QCD QD RCO74x163 CLKCLRLDENPENTA QAB QBC QCD QD RCO74x163+5VX8.38 CLKCLRLDENPENTA QAB QBC QCD QD RCO74x163 CLKCLRLDENPENTA QAB QBC QCD QD RCO74x16300010000+5VCLOCKCLR_LIf dont use any gates, only ca

6、n use 0 to start load or clr! 10000000-00000000? OK?10000000-11111111-00000000then load 10000000 Yes8-42To get even spacing(平均的间隔), the strategy is for the MSB (N3) to select half the states, the ones where QA is 0. The next bit down (N2) selects one-fourth of the states, the ones where QB is 0 and the less significant counter bits (i.e.,QA) are all 1. Likewise, N1 selects the one-eighth of the states where QC is 0 and QB and QA are 1, and N0 selects the state where QD is 0 and QC, QB