Question 7.2: Construct the MOD-10 counter with 74LS93...

Using the gated reset inputs, { R}_{0(\mathrm{1})},{ R}_{0(\mathrm{2})}. , partially decode count 1010. The first step is to construct aMOD- 16 counter by connecting Q_{0} output to the  {CP_{B}} input. Then the next step is to determine the connection of reset input. For the MOD-10 counter, the counter counts up from 0000 to 1001, so when it goes to 1001, the next state should be 0000 to make the counter recycle back, as shown in Table 7.1.4. Normally, the next state after 1001 is 1010; it can be observed that Q_{0}  and {Q}_{3} are both HIGH. Since {Q}_{3} and Q_{1} are both HIGH when it counts 1010, the counter can recycle by connecting {Q}_{3} , Q_{1} with { R}_{0(\mathrm{1})},{ R}_{0(\mathrm{2})}. , respectively, as shown in Figure 7.1.9. Notice that an extra state is needed for the asynchronous clear, and the counter must go into the 1010 state for several nanoseconds before recycling.