60 second timer
Our assignment was to build a circuit, using J/K flip flops for the tens place and a 74LS163 MSI counter for the ones place, that counts from 00 to 60 (resetting once 60 is detected). This counter is synchronous, since all segments are clocked by an external clock. This means that there will be no delay, or "ripple" effect, and the circuit will resemble an actual timer.
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pld Circuit
The 60 Second Timer and the DMV Counter are very similar, but have some slight differences. The obvious difference is that one counts to 60 and then resets to zero, while the other counts to 80 and then remains at 80 unless the reset is toggled. This is because the 60 Second Timer uses J/K flip flops in addition to a 74LS163 chip.
conclusion
- Asynchronous counters, the flip flops are wired to each other rather than the output, which causes a delay in the transfer between flip flops. In synchronous circuits, the clock goes directly to each input, so the transfer between flip flops is in sync.
- A 74LS163 chip has a synchronous load and clear, unlike that of the 74LS193 chip, which is asynchronous. While 74LS163 can only count up, 74LS193 can count up or down.
- First, I made the one's place circuit with the 74LS163 chip. I connected A, B, C, and D to ground so that the count would begin at zero. Next, I connected the outputs to a 4 input NAND gate to detect a 9. I connected this NAND gate and the reset button to an AND gate. I connected this AND gate to the load input on the 74LS163 chip so that the one's place circuit resets to zero after detecting 9. This output becomes the input of the first J/K flip flop for the 10s place circuit, which conisists of three J/K flip flops. The J, K, and Preset pins of each flip flop is connected to power. The not Q output of the first two flip flops are connected to the input of the second and third flip flops. There is a three input NAND gate that detects 6. This NAND gate and the reset are connected to an AND gate, which is connected to the clear pins of the flip flops, which resets both ciruits to zero.
- All of my classmates used the same components that I did.