4-Bit Ripple Down-Counter
Timers, watchdog circuits, and timeout mechanisms often rely on asynchronous down-counters for hardware simplicity and low power. The ripple down-counter cascades flip-flops to decrement a binary value on every clock cycle without requiring a global synchronous clock network.
Construct a 4-bit ripple down-counter. The outputs Q3, Q2, Q1, and Q0 must decrement by one on each falling edge of the clk signal. The count sequence wraps from 0 back to 15. Assume all flip-flops initialize to 0.
| clk falling edges | Q3 | Q2 | Q1 | Q0 | |---------------------|------|------|------|------| | 0 (Initial) | 0 | 0 | 0 | 0 | | 1 | 1 | 1 | 1 | 1 | | 2 | 1 | 1 | 1 | 0 | | 3 | 1 | 1 | 0 | 1 | | 4 | 1 | 1 | 0 | 0 |
Constraints
- Implement an asynchronous ripple architecture.
- Connect the
clkinput exclusively to the clock pin of theQ0stage. - Clock every subsequent stage using an output from the immediately preceding stage.
Topics
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