Concept: Uses fixed hardware logic (AND, OR, NOT, flip-flops) to generate control signals.

Operation: Opcode from IR enters combinational logic, which produces the necessary control signals for each timing step.

Characteristics:

• Fast: No memory lookup.
• Inflexible: Cannot easily modify instruction set.
• Complex: Large ISAs increase design difficulty.

Best For: RISC systems.

Concept: Uses a small memory called Control Store to hold microinstructions (microcode) that define control signals.

Operation:

Opcode → Control Store address.

Control Store outputs microinstructions.

Each microinstruction sets control lines for one micro-operation.

Microprogram Counter (µPC) steps through sequence.

Characteristics:

• Flexible: Easily modified or updated.
• Slower: Requires memory access to fetch microinstructions.
• Simpler hardware.

Best For: CISC systems.