Flags

Flags Generation Board

Comparison and status flag generation

Function

Generate 4 flags for ALU status and comparison:

• LESS: A < B (magnitude comparison)
• EQUAL: A == B (equality check)
• POSITIVE: OUT > 0 (positive result)
• COUT: Carry out (from adder)

Schematic

 Flags generation circuit

Flag Implementations

EQUAL Flag (~100T)

Function: Detect A == B

Logic:

EQUAL = ~((A[7] XOR B[7]) | (A[6] XOR B[6]) | ... | (A[0] XOR B[0]))

Implementation:

• 8× XOR gates (96T)
• 8-input NOR gate (16T)

LESS Flag (~120T)

Function: Detect A < B

Logic: Cascaded priority comparison (MSB first)

Implementation: ~120T comparator logic

POSITIVE Flag (~20T)

Function: Detect OUT > 0

Logic:

NOT_ZERO = OUT[7] | ... | OUT[0]
POSITIVE = ~OUT[7] & NOT_ZERO

COUT Flag (0T)

Function: Pass carry from adder

Implementation: Direct wire

Signals

Inputs:

• A[7:0], B[7:0] - For comparison
• OUT[7:0] - For POSITIVE detection
• COUT_IN - From adder

Outputs:

• LESS, EQUAL, POSITIVE, COUT

Last Updated: 2026-01-16