Memory Similarity Calculator Skill

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

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

Overview

The MemorySimilarityCalculator compares memory ICs based on:

Equivalent groups - Cross-manufacturer equivalents
Memory type - EEPROM, Flash, etc.
Interface - I2C, SPI
Capacity - Must match for high similarity
Voltage range - Operating voltage compatibility

Applicable Types

ComponentType.MEMORY
// Any type starting with "MEMORY_"
// Returns true for null to handle unrecognized memory devices

Similarity Thresholds

HIGH_SIMILARITY = 0.9;   // Equivalent parts
MEDIUM_SIMILARITY = 0.7; // Same type/interface, close specs
LOW_SIMILARITY = 0.3;    // Different capacity or interface

I2C EEPROM Equivalents

| Capacity | Equivalent Parts | |----------|------------------| | 256Kbit | 24LC256, AT24C256, M24C256, CAT24C256 | | 512Kbit | 24LC512, AT24C512, M24C512, CAT24C512 | | 1Mbit | 24LC1024, AT24C1024, M24C1024 |

calculator.calculateSimilarity("24LC256", "AT24C256", registry);
// Returns >= 0.7 (equivalent I2C EEPROMs)

SPI EEPROM Equivalents

| Capacity | Equivalent Parts | |----------|------------------| | 256Kbit | 25LC256, 25AA256, AT25256, M95256 | | 512Kbit | 25LC512, 25AA512, AT25512, M95512 |

SPI Flash Equivalents

| Capacity | Equivalent Parts | |----------|------------------| | 32Mbit | W25Q32JV, W25Q32FW, MX25L3233F, S25FL032P, IS25LP032 | | 64Mbit | W25Q64JV, W25Q64FW, MX25L6433F, S25FL064P, IS25LP064 | | 128Mbit | W25Q128JV, W25Q128FW, MX25L12833F, S25FL128, IS25LP128 |

calculator.calculateSimilarity("W25Q32JV", "MX25L3233F", registry);
// Returns >= 0.3 (same capacity SPI Flash)

Interface Rules

I2C and SPI memory have lower similarity due to different interfaces:

calculator.calculateSimilarity("24LC256", "25LC256", registry);
// Returns <= 0.7 (same capacity, different interface)

Capacity Rules

Different capacities return LOW_SIMILARITY:

calculator.calculateSimilarity("W25Q32JV", "W25Q128JV", registry);
// Returns 0.3 (same family, different size)

Package Handling

Package codes don't significantly affect similarity for memory:

Same memory, different package = HIGH_SIMILARITY (0.9)
Same memory, compatible package = HIGH_SIMILARITY (0.9)
Same memory, different package type = ~0.8

Manufacturer Prefixes

| Prefix | Manufacturer | Type | |--------|--------------|------| | 24LC | Microchip | I2C EEPROM | | AT24C | Atmel/Microchip | I2C EEPROM | | M24C | ST | I2C EEPROM | | CAT24C | ON Semi | I2C EEPROM | | 25LC/25AA | Microchip | SPI EEPROM | | AT25 | Atmel/Microchip | SPI EEPROM | | M95 | ST | SPI EEPROM | | W25Q | Winbond | SPI Flash | | MX25L | Macronix | SPI Flash | | S25FL | Spansion/Cypress | SPI Flash | | IS25LP | ISSI | SPI Flash |

Test Examples

// Same I2C EEPROM
calculator.calculateSimilarity("24LC256", "24LC256", registry);
// Returns 1.0

// Cross-manufacturer I2C EEPROM
calculator.calculateSimilarity("24LC256", "AT24C256", registry);
// Returns >= 0.7

// Same Flash, different manufacturer
calculator.calculateSimilarity("W25Q64JV", "MX25L6433F", registry);
// Returns >= 0.3

// Different capacity
calculator.calculateSimilarity("24LC256", "24LC512", registry);
// Returns 0.3

Metadata-Driven Implementation (January 2026)

Status: ✅ Converted (PR #117)

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

Specs Compared

| Spec | Importance | Tolerance Rule | Description | |------|-----------|----------------|-------------| | memoryType | CRITICAL | exactMatch | EEPROM, Flash, SRAM, etc. | | capacity | CRITICAL | exactMatch | 256Kbit, 512Kbit, 1Mbit, etc. | | interface | HIGH | exactMatch | I2C, SPI, Parallel | | package | LOW | exactMatch | SOIC, DIP, TSSOP, etc. |

Implementation Pattern

// Short-circuit check for CRITICAL incompatibility
if (!memoryType1.isEmpty() && !memoryType2.isEmpty() && !memoryType1.equals(memoryType2)) {
    return LOW_SIMILARITY;
}
if (!capacity1.isEmpty() && !capacity2.isEmpty() && !capacity1.equals(capacity2)) {
    return LOW_SIMILARITY;
}

// Weighted spec scoring
// memoryType: CRITICAL (1.0 weight)
// capacity: CRITICAL (1.0 weight)
// interface: HIGH (0.7 weight)
// package: LOW (0.2 weight)

Behavior Changes

| Comparison | Legacy Result | Metadata Result | Notes | |-----------|--------------|-----------------|-------| | 24LC256 vs 24LC256 | 1.0 | 1.0 | Identical | | 24LC256 vs AT24C256 | 0.7+ | 0.85 | Equivalent I2C EEPROM | | W25Q32JV vs MX25L3233F | 0.3+ | 0.61 | Same capacity Flash | | 24LC256 vs 24LC512 | 0.3 | 0.3 | Short-circuit on capacity | | W25Q32JVSSIQ vs W25Q32JVSFIQ | 0.7+ | 0.93 | Same Flash, different package |

Why more accurate: Metadata approach prioritizes capacity and type matching, with interface as secondary concern.

Learnings & Quirks

Part Number Patterns

24xx = I2C interface, 25xx = SPI interface
C often indicates CMOS
Capacity in Kbits: 256 = 32KB, 512 = 64KB, 1024 = 128KB

Revision Suffixes

JV, FW, JW on Winbond = package/voltage variants
A, B, C suffixes = revisions (usually compatible)

Voltage Compatibility

Standard: 2.7V-5.5V
Low voltage: 1.7V-3.6V (check compatibility)