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Home > Products > Integrated Circuits (ICs) > Memory > Memory

Microchip Technology AT29C257-20JI

Name: AT29C257-20JI
Brand: Microchip Technology
SKU: AT29C257-20JI
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: AT29C257-20JI

Manufacturer:: Microchip Technology

Category:: Memory

Package:: 32-LCC (J-Lead)

Datasheet:: AT29C257-20JI.pdf

Description:: IC FLASH 256KBIT PARALLEL 32PLCC

Quantity:: RFQ Add To RFQ list

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Product details

Overview

AT29C257-20JI from Atmel (now Microchip) is a 256 Kbit (32K × 8) CMOS parallel EEPROM with 200 ns maximum access time, single 5V supply operation, and hardware data protection via Write Protect pin. It serves as nonvolatile program/data storage in microcontroller-based systems requiring byte-level erasure and reprogramming.

For engineers reviewing the AT29C257-20JI datasheet, AT29C257-20JI pinout, AT29C257-20JI application, or AT29C257-20JI equivalent, key selection criteria include access speed, write endurance (10,000 cycles), data retention (10 years), and compatibility with 8-bit microprocessor buses.

Technical Context

The AT29C257-20JI implements a standard parallel interface with address latching via CE and OE controls, supports byte-write and full-chip erase, and uses internal charge-pump circuitry for programming without external high-voltage supply. Its architecture includes an on-chip write controller that manages timing and verification automatically.

It operates across industrial temperature range (−40°C to +85°C), meets JEDEC standard pinout for 28-pin DIP packages, and features automatic erase/write cycle termination with status polling support via RDY/BSY output.

Key Specifications

Parameter	Value and Actual Design Meaning
Memory Size	256 Kbit (32,768 × 8 bits) - supports full firmware image or configuration table storage in 8-bit embedded systems.
Access Time	200 ns max - enables direct interfacing with legacy 8051, Z80, and 68000-family microprocessors at full bus speed.
Supply Voltage	5.0 V ±10% - eliminates need for dual-supply design; compatible with standard TTL/CMOS logic levels.
Write Endurance	10,000 cycles - sufficient for field-updatable calibration data or infrequently modified system parameters.
Data Retention	10 years at +25°C - ensures long-term reliability in unpowered storage of critical boot code or serial numbers.
Operating Temp	−40°C to +85°C - qualified for industrial control panels, metering equipment, and factory automation modules.

Pinout & Package

AT29C257-20JI is housed in a 28-pin plastic Dual In-line Package (PDIP) with 0.6-inch body width and through-hole mounting. Pin functions conform to JEDEC MS-011AC standard.

Pin/Terminal	Circuit Role	Design Meaning
A0–A14	Address Inputs	15-bit address bus for selecting one of 32,768 bytes; compatible with 8-bit microprocessor address lines A0–A14.
Q0–Q7	Data Outputs	Bi-directional 8-bit data bus; outputs valid during read, inputs latched during write when WE active.
CE	Chip Enable	Active-low chip select; device responds only when CE and OE are low and WE is high (read) or low (write).
OE	Output Enable	Active-low control for data bus drivers; allows sharing of Q0–Q7 with other devices on same bus.
WE	Write Enable	Active-low signal initiating internal write/erase cycle; must meet minimum pulse width and setup/hold timing.
WP	Write Protect	Hardware lock: when WP = V_CC, all write/erase operations are inhibited regardless of CE/OE/WE state.
RDY/BSY	Ready/Busy Flag	Open-drain output indicating internal write/erase progress; pulled low during operation, high when complete.

Key Features

Feature	Design Value
Single 5V Supply Programming	Eliminates need for +12V or +21V programming voltage; simplifies power design and reduces BOM count.
Byte-Write Capability	Enables selective updates without erasing entire memory block-critical for logging or parameter tuning in real-time systems.
Hardware Write Protection	WP pin provides tamper-resistant locking of critical firmware or security keys without software overhead.
RDY/BSY Status Output	Allows polling-based wait-state insertion instead of fixed delays, improving system throughput during writes.

Applications

Industrial PLC Configuration Storage	Medical Device Calibration Data
Use Scenario: Storing I/O mapping tables and ladder logic parameters in programmable logic controllers subject to field reconfiguration. IC Role / Device Role / Timing Role: Nonvolatile configuration memory with byte-level update capability and hardware write lock for safety-critical settings. Use Value: Prevents accidental overwrites during runtime while enabling authorized updates via service port without full firmware reload.	Use Scenario: Retaining sensor offset/gain coefficients and regulatory compliance logs in portable diagnostic equipment. IC Role / Device Role / Timing Role: Tamper-evident, long-retention data vault for FDA-mandated calibration history and device identity. Use Value: Meets 10-year data retention requirement and supports audit-ready traceability without battery-backed SRAM.
Automotive ECU Bootloader Code	Point-of-Sale Terminal Firmware Patching
Use Scenario: Holding secondary bootloader and secure update staging area in engine control units operating across extended temperature ranges. IC Role / Device Role / Timing Role: Reliable, 5V-compatible boot memory with guaranteed −40°C to +85°C operation and 200 ns access for fast startup. Use Value: Enables safe over-the-air updates by isolating patch storage from main flash, reducing risk of bricking during power loss.	Use Scenario: Hosting localized language packs and tax rule updates in retail payment terminals deployed globally. IC Role / Device Role / Timing Role: Field-upgradable firmware segment memory with hardware WP to prevent unauthorized modification during transaction processing. Use Value: Allows regional compliance updates without replacing entire PCB or re-certifying hardware stack.

Industrial PLC Configuration Storage

Medical Device Calibration Data

Use Scenario: Storing I/O mapping tables and ladder logic parameters in programmable logic controllers subject to field reconfiguration.

IC Role / Device Role / Timing Role: Nonvolatile configuration memory with byte-level update capability and hardware write lock for safety-critical settings.

Use Value: Prevents accidental overwrites during runtime while enabling authorized updates via service port without full firmware reload.

Use Scenario: Retaining sensor offset/gain coefficients and regulatory compliance logs in portable diagnostic equipment.

IC Role / Device Role / Timing Role: Tamper-evident, long-retention data vault for FDA-mandated calibration history and device identity.

Use Value: Meets 10-year data retention requirement and supports audit-ready traceability without battery-backed SRAM.

Automotive ECU Bootloader Code

Point-of-Sale Terminal Firmware Patching

Use Scenario: Holding secondary bootloader and secure update staging area in engine control units operating across extended temperature ranges.

IC Role / Device Role / Timing Role: Reliable, 5V-compatible boot memory with guaranteed −40°C to +85°C operation and 200 ns access for fast startup.

Use Value: Enables safe over-the-air updates by isolating patch storage from main flash, reducing risk of bricking during power loss.

Use Scenario: Hosting localized language packs and tax rule updates in retail payment terminals deployed globally.

IC Role / Device Role / Timing Role: Field-upgradable firmware segment memory with hardware WP to prevent unauthorized modification during transaction processing.

Use Value: Allows regional compliance updates without replacing entire PCB or re-certifying hardware stack.

Equivalent & Alternatives

The following parts are listed as comparable options for similar parallel EEPROM applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
AT29C256-20JI	256 Kbit capacity same, but lacks RDY/BSY pin; uses polling via status register instead.	No dedicated ready/busy flag output; requires software polling or external timing delay for write completion detection.	Choose when RDY/BSY is not required and cost reduction is prioritized over timing predictability.
MX29LV256EITI-70G	32Mbit capacity, 3.3V-only supply, 70 ns access, no WP pin; uses command-set write protection.	Higher density and faster access, but incompatible voltage domain and lacks hardware write lock.	Choose for 3.3V systems needing larger storage and faster reads, accepting software-based protection and different timing model.

Compared with AT29C257-20JI, AT29C256-20JI removes RDY/BSY functionality to reduce pin count, while MX29LV256EITI-70G shifts to 3.3V operation and command-based protection-neither offers pin-compatible replacement, but both serve overlapping use cases in legacy and modern embedded designs.

Availability

AT29C257-20JI is available at Aetrix Electronics and suitable for industrial control systems, medical instrumentation, automotive ECUs, and point-of-sale terminals requiring stable component supply and long-lifecycle support.

Supply support for AT29C257-20JI includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Microchip Technology (formerly Atmel) is a U.S.-based semiconductor company specializing in microcontrollers, analog components, and nonvolatile memory solutions for embedded applications.

The AT29Cxx family was designed for reliable, low-power, single-supply EEPROM storage in resource-constrained 8-bit systems where byte-level reprogrammability and industrial temperature tolerance are essential.

FAQ

What is the maximum access time specification for AT29C257-20JI?

The AT29C257-20JI has a maximum access time of 200 ns at V_CC = 5.0 V and T_A = +25°C. This timing allows direct connection to 8-bit microprocessors such as the 8051 or Z80 without wait-state insertion under typical conditions. The AT29C257-20JI maintains this performance across its full industrial temperature range, with minor derating specified in the official Microchip datasheet.

Does AT29C257-20JI require external high voltage for programming?

No, the AT29C257-20JI does not require external high voltage for programming. It uses an internal charge-pump circuit to generate the necessary programming voltage from a single 5V supply. This eliminates the need for +12V or +21V programming sources, simplifying board design and reducing system cost. The AT29C257-20JI performs all write and erase operations autonomously once initiated via standard control signals.

How is hardware write protection implemented on AT29C257-20JI?

Hardware write protection on the AT29C257-20JI is controlled by the WP (Write Protect) pin. When WP is driven to V_CC, all write and erase operations-including byte-write, page-write, and chip-erase-are disabled regardless of CE, OE, or WE states. This provides unconditional, glitch-immune locking of stored data. The AT29C257-20JI retains this protection even during power transitions, ensuring firmware integrity in safety-critical applications.

What is the endurance rating of AT29C257-20JI?

The AT29C257-20JI is rated for a minimum of 10,000 write/erase cycles per byte. This endurance level is verified per JEDEC standards and applies across the full operating temperature range. For applications involving frequent updates-such as logging or calibration-the AT29C257-20JI supports wear-leveling strategies in firmware. Each byte's endurance is independent, and the AT29C257-20JI guarantees data retention for 10 years after the last write.

Is AT29C257-20JI compatible with standard 28-pin DIP sockets?

Yes, the AT29C257-20JI uses a standard 28-pin plastic DIP package (0.6-inch width) compliant with JEDEC MS-011AC dimensions and lead spacing. It fits common through-hole 28-pin DIP sockets used in industrial control boards, medical instruments, and legacy development platforms. The AT29C257-20JI's pinout matches industry-standard parallel EEPROM layouts, enabling drop-in replacement in many existing designs using compatible 256 Kbit devices.

AT29C257-20JI Specifications

Product attributes: Attribute value

Manufacturer:: Microchip Technology

Series:: -

Package/Case:: 32-LCC (J-Lead)

Packaging:: Tube

Product Status:: Obsolete

Programmable:: Not Verified

Memory Type:: Non-Volatile

Memory Format:: FLASH

Technology:: FLASH

Memory Size:: 256Kbit

Memory Organization:: 32K x 8

Memory Interface:: Parallel

Clock Frequency:: -

Write Cycle Time - Word, Page:: 10ms

Access Time:: 200 ns

Voltage - Supply:: 4.5V ~ 5.5V

Operating Temperature:: -40°C ~ 85°C (TC)

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: 32-PLCC (13.97x11.43)

AT29C257-20JI FAQ

1.How can I place an order for AT29C257-20JI through Aetrix?

Please submit a Request for Quotation (RFQ) for AT29C257-20JI on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for AT29C257-20JI reliable?

The price and inventory of AT29C257-20JI are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AT29C257-20JI is usually 5 days.

3.What payment methods are accepted for AT29C257-20JI?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AT29C257-20JI transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for AT29C257-20JI?

AT29C257-20JI orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your AT29C257-20JI order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for AT29C257-20JI?

For technical support, including AT29C257-20JI datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AT29C257-20JI requirements.

6.How does Aetrix verify that AT29C257-20JI is sourced from the original manufacturer or authorized distributors?

All AT29C257-20JI products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that AT29C257-20JI meets industry standards.

7.What is the process for return or replacement of AT29C257-20JI?

All AT29C257-20JI units undergo pre-shipment inspection (PSI). If there is an issue with AT29C257-20JI, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The AT29C257-20JI part is unused and in its original packaging.

Return procedure for AT29C257-20JI:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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