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

Microchip Technology AT29C257-70JI-T

Name: AT29C257-70JI-T
Brand: Microchip Technology
SKU: AT29C257-70JI-T
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: AT29C257-70JI-T

Manufacturer:: Microchip Technology

Category:: Memory

Package:: 32-LCC (J-Lead)

Datasheet:: AT29C257-70JI-T.pdf

Description:: IC FLASH 256KBIT PARALLEL 32PLCC

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Product details

Overview

AT29C257-70JI-T from Microchip Technology (formerly Atmel) is a 256 Kbit (32K × 8) 5-V-only in-system Flash PEROM memory IC used for firmware storage and code execution in embedded controllers. It delivers 70 ns read access time, 10 ms page program time, 10 ms chip erase time, and supports hardware/software data protection. It operates across -40°C to +85°C and is commonly deployed in industrial PLCs and legacy microcontroller boot loaders.

For engineers reviewing the AT29C257-70JI-T datasheet, AT29C257-70JI-T pinout, AT29C257-70JI-T application, or AT29C257-70JI-T equivalent, key selection considerations include its PLCC-32 package, 5V-only reprogramming compatibility, DATA polling and toggle-bit programming status detection, and pin-compatibility with AT29C010A and AT29C512 for memory upgrades.

Technical Context

The AT29C257-70JI-T implements a page-based Flash architecture where 64-byte pages are loaded and programmed in a single internal cycle using on-chip timers and latches. Its operation mimics SRAM read timing but adds dedicated software command sequences (e.g., 5555h/2AAAh/80h) for chip erase and data protection enable/disable.

Hardware protection includes V_CC sense (<3.8 V inhibits programming), 5 ms power-on delay, and noise filtering (<15 ns pulses ignored). Programming requires OE high, CE low, WE low, and valid A6–A14 page address during each byte load - all verified via AC waveforms and timing tables in the official datasheet.

Key Specifications

Parameter	Value and Actual Design Meaning
Memory Size	256 Kbit (32,768 × 8), sufficient for full boot code or configuration tables in 8-bit microcontrollers.
Read Access Time	70 ns max - enables direct execution from memory without wait states on 14 MHz bus systems.
Page Program Time	10 ms typical - defines minimum interval between successive 64-byte writes during firmware updates.
Chip Erase Time	10 ms typical - allows full device reset before reprogramming, critical for field firmware recovery.
Endurance	>10,000 write/erase cycles per sector - supports long-term field calibration data logging.
Supply Voltage	5 V ± 10% - compatible with legacy 5V logic rails without level-shifting circuitry.
Standby Current	300 µA CMOS - enables low-power retention in battery-backed industrial modules.

Pinout & Package

AT29C257-70JI-T is housed in a 32-lead Plastic Leaded Chip Carrier (PLCC) package with J-leads, rated for industrial temperature (-40°C to +85°C) and RoHS-compliant.

Pin/Terminal	Circuit Role	Design Meaning
A0–A14	Address Inputs	15-bit address bus supporting full 32K-word addressing; A6–A14 define page address during programming.
I/O0–I/O7	Bidirectional Data Bus	8-bit parallel interface; carries both input data during programming and output data during read operations.
CE	Chip Enable	Active-low chip select; must be low for read, program, or erase; enables hardware write inhibition when high.
OE	Output Enable	Active-low output control; must be high during programming to prevent bus contention.
WE	Write Enable	Active-low write strobe; controls byte loading and initiates internal program/erase cycles when CE is low.
NC	No Connect	Unbonded pin; must remain unconnected per design - no pull-up/down or routing required.

Key Features

Feature	Design Value
5-V-only reprogramming	Eliminates need for 12 V programming voltage, simplifying power supply design and enabling in-system updates via standard logic-level signals.
DATA polling & toggle-bit detection	Allows real-time monitoring of program/erase completion without external timers or interrupts - I/O7 complement or I/O6 toggling indicates active cycle.
Software data protection	User-configurable lock via 3-byte command sequence (5555h/2AAAh/80h); prevents accidental writes during power transitions or noise events.
Hardware data protection	V_CC sensing, 5 ms power-on delay, and noise filtering ensure robustness against brown-out and EMI-induced spurious writes.
Pin-compatible upgrade path	Direct replacement for AT29C010A (1 Mbit) and AT29C512 (64 Kbit) in same PLCC-32 footprint - enables memory scaling without PCB redesign.

Applications

Industrial PLC Firmware Storage	Legacy Microcontroller Boot Loader
Use Scenario: Storing ladder logic firmware and I/O mapping tables in programmable logic controllers operating continuously in factory environments. IC Role / Device Role / Timing Role: Nonvolatile code storage with fast read access and field-upgradable Flash memory; serves as primary boot ROM. Use Value: 70 ns access time enables zero-wait-state execution; 10,000-cycle endurance supports decades of firmware revisions in unattended deployments.	Use Scenario: Hosting boot code for 8051 or Z80-based embedded systems where BIOS initialization and peripheral setup occur before RAM initialization. IC Role / Device Role / Timing Role: Read-only memory mapped at reset vector; provides deterministic startup behavior independent of volatile RAM state. Use Value: CMOS/TTL compatibility ensures seamless integration with legacy bus interfaces; 5V-only operation avoids dual-supply complexity.
Medical Device Configuration Memory	Automotive Diagnostic Module Storage
Use Scenario: Retaining calibration coefficients, safety thresholds, and user preferences in Class II medical instruments requiring traceable, tamper-resistant settings. IC Role / Device Role / Timing Role: Secure parameter storage with software/hardware write protection; accessed only during service mode or power-up. Use Value: Dual-layer protection (V_CC sense + 3-byte unlock) prevents unintended changes during ESD events or voltage dips - critical for regulatory compliance.	Use Scenario: Storing OBD-II protocol stacks and vehicle-specific diagnostic routines in aftermarket scan tools operating across automotive battery voltage ranges. IC Role / Device Role / Timing Role: Field-programmable firmware repository supporting multi-vehicle protocol updates via USB host interface. Use Value: 5V ±10% supply tolerance accommodates 9–16 V automotive transients; PLCC-32 package withstands thermal cycling in under-hood environments.

Industrial PLC Firmware Storage

Legacy Microcontroller Boot Loader

Use Scenario: Storing ladder logic firmware and I/O mapping tables in programmable logic controllers operating continuously in factory environments.

IC Role / Device Role / Timing Role: Nonvolatile code storage with fast read access and field-upgradable Flash memory; serves as primary boot ROM.

Use Value: 70 ns access time enables zero-wait-state execution; 10,000-cycle endurance supports decades of firmware revisions in unattended deployments.

Use Scenario: Hosting boot code for 8051 or Z80-based embedded systems where BIOS initialization and peripheral setup occur before RAM initialization.

IC Role / Device Role / Timing Role: Read-only memory mapped at reset vector; provides deterministic startup behavior independent of volatile RAM state.

Use Value: CMOS/TTL compatibility ensures seamless integration with legacy bus interfaces; 5V-only operation avoids dual-supply complexity.

Medical Device Configuration Memory

Automotive Diagnostic Module Storage

Use Scenario: Retaining calibration coefficients, safety thresholds, and user preferences in Class II medical instruments requiring traceable, tamper-resistant settings.

IC Role / Device Role / Timing Role: Secure parameter storage with software/hardware write protection; accessed only during service mode or power-up.

Use Value: Dual-layer protection (V_CC sense + 3-byte unlock) prevents unintended changes during ESD events or voltage dips - critical for regulatory compliance.

Use Scenario: Storing OBD-II protocol stacks and vehicle-specific diagnostic routines in aftermarket scan tools operating across automotive battery voltage ranges.

IC Role / Device Role / Timing Role: Field-programmable firmware repository supporting multi-vehicle protocol updates via USB host interface.

Use Value: 5V ±10% supply tolerance accommodates 9–16 V automotive transients; PLCC-32 package withstands thermal cycling in under-hood environments.

Equivalent & Alternatives

The following parts are listed as comparable options for similar Flash memory applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
AT29C040A-70JI	512 Kbit (64K × 8), same PLCC-32 package, 70 ns access, but requires 12 V for chip erase (not 5 V only).	Larger capacity suits extended firmware images; lacks full 5V-only reprogrammability - needs HV generator circuitry.	Select when >256 Kbit storage is needed and HV support is acceptable; not drop-in for AT29C257-70JI-T due to erase voltage requirement.
SST39SF040-70-4C-NHE	512 Kbit Flash, 70 ns access, 3.3 V/5 V tolerant, but uses different command set and lacks hardware V_CC sense protection.	Designed for mixed-voltage systems; no native 5V-only programming - requires voltage translation for legacy 5V buses.	Choose for new designs targeting lower power or dual-voltage flexibility; not pin- or command-compatible with AT29C257-70JI-T.

Compared with AT29C040A-70JI and SST39SF040-70-4C-NHE, the AT29C257-70JI-T uniquely combines true 5V-only reprogramming, integrated hardware write protection, and verified pin-compatibility with earlier Atmel Flash devices - making it optimal for maintaining legacy industrial designs without layout or firmware changes.

Availability

AT29C257-70JI-T is available at Aetrix Electronics and suitable for industrial PLCs, legacy microcontroller boot loaders, medical device configuration storage, and automotive diagnostic module firmware requiring stable component supply across extended temperature ranges.

Supply support for AT29C257-70JI-T 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 acquired Atmel in 2016 and maintains full support for legacy Atmel Flash memory products including the AT29C257 family.

The AT29C257-70JI-T belongs to Atmel's early-generation 5V Flash PEROM product line, designed specifically for in-system upgradability of firmware and configuration data in industrial and embedded systems without requiring high-voltage programming infrastructure.

FAQ

What is the operating temperature range for AT29C257-70JI-T?

The AT29C257-70JI-T is rated for industrial temperature operation from -40°C to +85°C. This specification is confirmed by the "I" suffix in the ordering code and validated in the DC and AC operating range table of the official datasheet. The PLCC-32 package and internal CMOS design ensure reliable performance across this full range without derating. AT29C257-70JI-T maintains 70 ns access time and full functionality throughout this interval.

Does AT29C257-70JI-T require a 12 V programming voltage?

No, AT29C257-70JI-T supports 5-V-only reprogramming - no 12 V supply is needed for page programming or chip erase. All operations use standard 5 V logic levels with specific software command sequences (e.g., 5555h/2AAAh/80h). This eliminates external HV circuitry and simplifies system design. The "70JI-T" suffix confirms full 5V-only compliance per Atmel's ordering information table.

How is programming status detected on AT29C257-70JI-T?

AT29C257-70JI-T supports two hardware-verified methods: DATA polling (monitoring complement on I/O7) and toggle-bit detection (observing I/O6 toggling). Both are defined in the datasheet's "Data Polling Characteristics" and "Toggle Bit Characteristics" sections. These mechanisms operate without external clocks or timers and are fully functional during the 10 ms internal program cycle - enabling deterministic firmware update sequencing in real-time systems.

Is AT29C257-70JI-T pin-compatible with AT29C010A?

Yes, AT29C257-70JI-T is explicitly stated as pin-compatible with AT29C010A and AT29C512 in the official datasheet's Features section. All three devices use the same PLCC-32 (32J) package and identical pin functions (A0–A14, I/O0–I/O7, CE, OE, WE, NC). This allows direct PCB replacement for memory upgrades without layout modification - a key design advantage confirmed in the "Pin-Compatible" feature bullet.

What protection mechanisms prevent accidental writes to AT29C257-70JI-T?

AT29C257-70JI-T implements dual-layer write protection: hardware-based (V_CC sense <3.8 V, 5 ms power-on delay, OE-high/CE-high/WE-high inhibit, and 15 ns noise filtering) and software-based (user-enabled 3-byte unlock sequence: 5555h/2AAAh/80h). Both are documented in the Device Operation section. These mechanisms operate independently - for example, software protection remains active across power cycles, while hardware protection responds instantly to voltage droop or noise.

AT29C257-70JI-T Specifications

Product attributes: Attribute value

Manufacturer:: Microchip Technology

Series:: -

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

Packaging:: Tape & Reel (TR)

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:: 70 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)

AT29C257-70JI-T FAQ

1.How can I place an order for AT29C257-70JI-T through Aetrix?

Please submit a Request for Quotation (RFQ) for AT29C257-70JI-T 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 AT29C257-70JI-T reliable?

The price and inventory of AT29C257-70JI-T are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AT29C257-70JI-T is usually 5 days.

3.What payment methods are accepted for AT29C257-70JI-T?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AT29C257-70JI-T transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for AT29C257-70JI-T?

AT29C257-70JI-T orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your AT29C257-70JI-T 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 AT29C257-70JI-T?

For technical support, including AT29C257-70JI-T datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AT29C257-70JI-T requirements.

6.How does Aetrix verify that AT29C257-70JI-T is sourced from the original manufacturer or authorized distributors?

All AT29C257-70JI-T 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 AT29C257-70JI-T meets industry standards.

7.What is the process for return or replacement of AT29C257-70JI-T?

All AT29C257-70JI-T units undergo pre-shipment inspection (PSI). If there is an issue with AT29C257-70JI-T, 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 AT29C257-70JI-T part is unused and in its original packaging.

Return procedure for AT29C257-70JI-T:

1.Submit a request within 90 days.

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

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