Projects
Build and document small digital systems. Your ticks are saved in this browser.
3×3 multiplier
Multiply two 3-bit numbers to get a 6-bit product. Partial products come from AND gates, and adders sum the shifted rows.
101 sequence detector
Design an FSM that raises its output when it sees 101. Decide Moore or Mealy and overlapping or not.
MOD-6 counter
Count 000 to 101 and return to 000. Decide between asynchronous reset and next-state logic.
Mini digital system
Combine input switches, combinational logic, a register, a counter, display logic and a control FSM into one small system.
Final project
Design a digital system from a written specification and document it.
Viva questions
1. Why are NAND and NOR universal gates?
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Each can build NOT (tie the inputs), and then AND and OR by DeMorgan’s laws, so any function can be built from one gate type.
2. When is a K-map useful?
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For simplifying functions of two to four variables (up to about six with care), because it shows adjacent minterms visually and gives minimal SOP or POS.
3. Combinational vs. sequential?
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Combinational outputs depend only on present inputs. Sequential outputs also depend on stored state.
4. Why are flip-flops clocked?
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The clock makes every state change happen at one known instant, which makes timing predictable and avoids races.
5. Decoder vs. encoder?
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A decoder turns a binary code into one active line. An encoder turns one active line into a binary code.
6. How can a MUX implement a Boolean function?
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Use the variables as select lines and connect the data inputs to the function values (constants, or the leftover variable and its complement).
7. How is the flip-flop count for a MOD-N counter found?
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The smallest n with 2ⁿ ≥ N.
8. Why is state reduction useful?
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Merging equivalent states can save flip-flops and combinational logic without changing the external behaviour.
9. How does memory decoding work?
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A decoder converts address bits into a single select line for a location or chip, and chip selects enable only the addressed device.
10. What are PLA and PAL?
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Programmable logic devices with an AND array and an OR array. In a PLA both are programmable. In a PAL only the AND array is.