Digital Electronics Expert

Before Starting

1. ASIC or FPGA implementation?
2. RTL design or verification focus?
3. Which HDL? Verilog or VHDL?

Core Expertise Areas

Boolean Logic

Boolean algebra: AND, OR, NOT operations, De Morgan theorems. Karnaugh map: minimize Boolean expressions graphically, group ones. Sum of products: canonical form from truth table, AND terms ORed together. NAND and NOR universality: any logic function implementable with only NAND or only NOR.

Combinational Logic

Multiplexer: select one of N inputs based on select lines. Decoder: N inputs to 2 to the N outputs, one-hot output. Adder: half adder, full adder, ripple carry, carry look-ahead. Comparator: outputs equal, greater than, less than for two binary numbers. Propagation delay: time for output to respond to input change.

Sequential Logic

D flip-flop: samples input on clock edge, most common storage element. Registers: parallel flip-flops share clock, store multi-bit values. Counters: binary, Gray code, up-down, synchronous and asynchronous. State machines: Moore and Mealy, state transition diagram, next state logic. Setup and hold time: data must be stable around clock edge for correct capture.

FPGA and HDL

FPGA architecture: LUT-based logic, flip-flops, block RAM, DSP slices, I/O. Verilog: hardware description language, structural and behavioral modeling. Synthesis: HDL converted to netlist of standard cells or FPGA primitives. Timing analysis: static timing analysis verifies setup and hold margins. Place and route: map netlist to physical FPGA resources, meet timing constraints.

Best Practices

• Synchronize all inputs to clock domain before using in logic
• Avoid latches by ensuring all paths in combinational always blocks have else clause
• Use synchronous reset for FPGA designs
• Run static timing analysis after every significant change

Common Pitfalls

Pitfall	Fix
Metastability from async inputs	Use two flip-flop synchronizer for all async signals
Inferred latches	Assign default values to all outputs in combinational logic
Clock domain crossing issues	Use proper CDC techniques with synchronizers
Timing violations ignored	Fix all timing violations before tapeout or deployment

Related Skills

• circuit-analysis-expert
• embedded-systems-expert
• vlsi-design-expert