Project Overview
We designed a 60 second timer that counts from 00 to 59 seconds then resets and repeats. For the ones display we had to build it with a synchronous counter (74LS163 MSI counter). For the tens display we had to build it with SSI logic gates (J/K). Both displays had to use a seven segment display driver.
Final Project Conclusions
- Asynchronous counters suffer from the ripple effect while synchronous counters don't. In synchronous counters all flip flops are connected to the same clock while asynchronous counters are connected to different clocks. Also Synchronous counters are faster and require more logic.
- 163 is only an up counter while 193 can be up or down. 163 shows the number it detects while 193 shows the number before the the one it detects. 163 has a synchronous load and clear while 193 has an asynchronous load and clear.
- To first start off this project I looked back at the 163 counters and SSI logic gates (J/K) to remind me on how they work again. I first built the 163 counter (ones unit display) because we did it more recently. I wired it so it would load a 0 and detect a 9. To detect a 9 I put B and C through an inverter and the LSB (A) and the MSB (D) without an inverter. I did this because 163 counters show the number they detect. This displayed 0-9. I then built the SSI logic gates (J/K) with 3 74ls76 chips. I connected all the loads to clear to load a 0. After that I connected all of the Q's to the hex display to detect a 7 and show a 6. At this point I realized we weren't supposed to use a hex display and had to use a 74LS48 BCD - to seven segment display driver. I deleted the hex displays and wired in the seven segment displays to make it work. Both of my circuits were working accordingly by themselves. I then had to make my tens work when my ones detected a 10. I tried many times to make it work but it never did. I then realized that I had to make it detect a 0 because it only goes from 0-9 and never goes to 10. Every time my ones showed a 0 my tens went up 1 until 60 when it reset back to 0. At this point I was almost finished and only needed a reset switch. I built a switch for the 163 chip first because I remembered it more clearly. All I did was build a switch and connect it to clear. To make my reset work for my SSI gates I inputted an AND gate right before the load and outputted it to all the clears. I then outputted the reset switch into the other input of the AND. This way if my switch was connected to ground both the ones and tens would be connected to clear and go to 0. At this point I was finished with my project and it worked exactly how it was supposed to.
- Yes some of my classmates built the circuit in PLD mode while I built it in Design mode. Their's was different because they had to use LED's for their output and didn't have a seven segment display.