Digital Logic Design and Microprocessors
Digital Logic Design and Microprocessors tests Boolean minimization, combinational and sequential building blocks, timing, and basic microprocessor organization. Expect K-maps, flip-flops, counters, decoders, memory maps, addressing modes, and interrupt behavior.
Core rules
- De Morgan: (AB)'=A'+B'; (A+B)'=A'B'.
- A combinational circuit has no state; sequential logic depends on present inputs and stored state.
- A D flip-flop captures input at the active clock edge; setup and hold windows must be met.
- Synchronous design uses one clock; asynchronous inputs need synchronization.
- A microprocessor fetches, decodes, and executes; addresses select memory or I/O.
Worked example
Simplify F(A,B,C)=Σm(1,3,5,7). All minterms have C=1 while A and B vary, so F=C. On a K-map, the four cells in the C=1 column form one group of four, eliminating A and B. A common error is to pair only adjacent 1s and miss the wrap-around group.
Traps
Do not treat don't-cares as 1s unless they enlarge a group. Active-low enable signals invert intuition: a bubble means assertion at 0. Mixing edge-triggered and level-sensitive devices creates race conditions. In microprocessor questions, distinguish physical addresses from port numbers and maskable from non-maskable interrupts. A clock-frequency increase does not fix setup violations; it worsens them.