similarity-logic

name	similarity-logic
description	Use when working with logic IC similarity calculations - comparing 74xx series, CD4000 CMOS, technology families (LS, HC, HCT), function groups (NAND, NOR, flip-flops), or logic IC-specific similarity logic.

Logic IC Similarity Calculator Skill

Guidance for working with LogicICSimilarityCalculator in the lib-electronic-components library.

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For metadata-driven similarity architecture, see /similarity-metadata:

• SpecImportance levels (CRITICAL, HIGH, MEDIUM, LOW, OPTIONAL)
• ToleranceRule types (exactMatch, percentageTolerance, minimumRequired, etc.)
• SimilarityProfile contexts (DESIGN_PHASE, REPLACEMENT, COST_OPTIMIZATION, etc.)
• Calculator integration patterns and gotchas

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Overview

The LogicICSimilarityCalculator compares logic ICs based on:

• Logic function - NAND, NOR, NOT, AND, OR, flip-flops, etc.
• Technology family - LS, ALS, HC, HCT, F, etc.
• Part number series - 74xx vs CD4000

Applicable Types

ComponentType.LOGIC_IC
ComponentType.LOGIC_IC_NEXPERIA
ComponentType.LOGIC_IC_DIODES
ComponentType.IC  // Generic IC type also supported

Returns false for null type.

Similarity Thresholds

HIGH_SIMILARITY = 0.9;   // Same function, compatible technology
MEDIUM_SIMILARITY = 0.5; // Related parts
LOW_SIMILARITY = 0.3;    // Different functions

74xx Series

Technology Families (Interchangeable within groups)

Family	Speed	Power	Compatible With
LS	Fast	Low	ALS, F, HC, HCT
ALS	Faster	Lower	LS, F, HC, HCT
F	Fast	Medium	LS, ALS, HC, HCT
HC	Fast	Very Low	LS, ALS, F, HCT
HCT	Fast	Very Low	LS, ALS, F, HC

// Compatible technologies = HIGH
calculator.calculateSimilarity("74LS00", "74HC00", registry);
// Returns 0.9

calculator.calculateSimilarity("74LS04", "74ALS04", registry);
// Returns 0.9

Function Groups

Function	Part Numbers
NAND Gates	00, 10, 20, 30, 40
NOR Gates	02, 12, 22, 32, 42
Inverters	04, 14, 24, 34, 44
AND Gates	08, 18, 28, 38, 48
OR Gates	32, 42
Flip-Flops	73, 74, 75, 76, 77, 78
Multiplexers	151, 153, 157, 158
Decoders	138, 139, 154, 155

// Different functions = LOW
calculator.calculateSimilarity("74LS00", "74LS74", registry);
// Returns 0.3 (NAND vs Flip-Flop)

CD4000 CMOS Series

Common CD4000 Parts

Part	Function
CD4001	Quad 2-input NOR
CD4011	Quad 2-input NAND
CD4013	Dual D flip-flop
CD4017	Decade counter
CD4040	12-bit binary counter
CD4051	8-channel mux
CD4066	Quad bilateral switch

CD4000 Package Codes

Suffix	Package
BE	PDIP (plastic)
BM	SOIC
UBE	Unbuffered PDIP
N, P	DIP variants
DG, PW, DR	SMD variants

// Same CD4000 IC, different package = HIGH
calculator.calculateSimilarity("CD4001BE", "CD4001BM", registry);
// Returns 0.9

// Different CD4000 ICs = LOW
calculator.calculateSimilarity("CD4001BE", "CD4011BE", registry);
// Returns 0.3

Cross-Series Comparison

74xx and CD4000 are generally not interchangeable:

// 74xx vs CD4000 with same function
calculator.calculateSimilarity("74HC00", "CD4011BE", registry);
// Returns LOW (different series, even if same function)

Test Examples

// Same 74xx, compatible technologies
calculator.calculateSimilarity("74LS00", "74HC00", registry);
// Returns 0.9

// Same CD4000 IC, different package
calculator.calculateSimilarity("CD4001BE", "CD4001BM", registry);
// Returns 0.9

// Same function group in 74xx
calculator.calculateSimilarity("74LS04", "74ALS04", registry);
// Returns 0.9

// Different functions
calculator.calculateSimilarity("74LS00", "74LS74", registry);
// Returns 0.3

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Learnings & Quirks

74xx Part Number Structure

74 LS 04 N
│  │  │  │
│  │  │  └── Package (N=DIP)
│  │  └───── Function (04=Inverter)
│  └──────── Technology (LS=Low-power Schottky)
└─────────── Series prefix

CD4000 Part Number Structure

CD 4001 BE
│  │    │
│  │    └── Package (BE=Plastic DIP)
│  └─────── Function number
└────────── Series prefix

Metadata-Driven Implementation (January 2026)

Status: ✅ Converted (PR #119)

The LogicICSimilarityCalculator now uses a metadata-driven approach with spec-based comparison.

Specs Compared

Spec	Importance	Tolerance Rule	Description
function	CRITICAL	exactMatch	NAND, NOR, NOT, AND, OR, flip-flop, etc.
series	HIGH	exactMatch	74xx vs CD4000
technology	MEDIUM	exactMatch	LS, HC, HCT, ALS, F, etc.
package	LOW	exactMatch	N, D, P, PW, etc.

Implementation Pattern

// Short-circuit check for CRITICAL incompatibility
if (!function1.isEmpty() && !function2.isEmpty() && !areSameFunction(mpn1, mpn2)) {
    return LOW_SIMILARITY;
}

// Short-circuit for series incompatibility (74xx vs CD4000)
if (!series1.isEmpty() && !series2.isEmpty() && !series1.equals(series2)) {
    return 0.0;
}

// Extract function from both 74xx and CD4000 series
private String extractFunction(String mpn) {
    if (mpn.matches("^CD4.*")) {
        // CD4001 → "001", CD4011 → "011"
        return cmosPatternMatcher.group(1);
    }
    // 74LS00 → "00", 74HC138 → "138"
    return ttlPatternMatcher.group(3);
}

Behavior Changes

Comparison	Legacy Result	Metadata Result	Notes
74LS00 vs 74HC00	0.9	0.88	Compatible technologies
CD4001BE vs CD4001BM	0.9	0.96	Same IC, different package
CD4001 vs CD4011	0.3	0.3	Short-circuit on function
74LS00 vs CD4001	undefined	0.0	Short-circuit on series

Why more accurate: Metadata approach correctly handles both 74xx and CD4000 series, with series check preventing false matches.

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Technology Compatibility Notes

• HC is CMOS, LS is TTL - but they're voltage compatible at 5V
• HCT is specifically designed for TTL compatibility
• 74LVC series is for 3.3V operation

Function Group Patterns

• The 2-digit function number after technology code determines function
• Same function number = same function across technologies