Microchip Technology AT29C257-12JI-T

Overview

AT29C257-12JI-T from Microchip Technology (formerly Atmel) is a 5-V-only, 256 Kbit (32K × 8) in-system reprogrammable Flash PEROM with 120 ns read access time, 64-byte page programming, and hardware/software data protection. It operates across –40°C to +85°C, draws 50 mA active current and 300 µA CMOS standby current, and supports pin-compatible upgrades from AT29C010A and AT29C512 in embedded firmware storage applications.

For engineers reviewing the AT29C257-12JI-T datasheet, AT29C257-12JI-T pinout, AT29C257-12JI-T application, or AT29C257-12JI-T equivalent, key selection criteria include its 120 ns tACC timing grade, PLCC-32 package, software-controlled chip erase via 6-byte command, DATA polling/Toggle Bit end-of-program detection, and dual hardware/software write protection for industrial firmware integrity.

Technical Context

The AT29C257-12JI-T implements a nonvolatile Flash architecture with internal address/data latches for 64-byte page loads, autonomous erase-and-program sequencing controlled by an on-chip timer, and dual-mode write enable (WE/CE-controlled byte load). Its operation requires no high-voltage programming supply - all commands execute at 5 V ±10%.

It supports three distinct operational modes: standard read (CE/OE low, WE high), page program (CE low, OE high, WE toggled), and software chip erase (6-byte command sequence to addresses 5555H/2AAAH). Data integrity is enforced via VCC sense (<3.8 V inhibits programming), noise filtering (<15 ns pulses ignored), and toggle-bit or DATA polling for cycle completion verification.

Key Specifications

Pinout & Package

AT29C257-12JI-T is housed in a 32-lead Plastic Leaded Chip Carrier (PLCC) package with J-bend leads, designed for surface-mount reflow assembly and socketed in-circuit programming.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SST39VF200A-70-4C-EKE and MX29LV256EITI-12G, the AT29C257-12JI-T uniquely delivers 5 V-only operation with integrated hardware write protection, PLCC-32 pinout compatibility with legacy Atmel Flash, and deterministic 10 ms page programming - critical for retrofitting industrial systems without board redesign.

Availability

AT29C257-12JI-T is available at Aetrix Electronics and suitable for industrial PLCs, automotive ECUs, medical diagnostic devices, and networking equipment requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for AT29C257-12JI-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 is a global semiconductor company specializing in microcontrollers, analog components, and Flash memory solutions, with a focus on reliability and long-term product availability.

The AT29C257-12JI-T belongs to Microchip's legacy parallel-interface Flash memory product line, engineered for industrial and automotive applications demanding in-system reprogrammability, robust data retention, and seamless migration from earlier Atmel Flash devices.

FAQ

What is the maximum operating temperature range for the AT29C257-12JI-T?

The AT29C257-12JI-T is rated for industrial operation from –40°C to +85°C. This range is confirmed by the "JI" suffix in the ordering code and validated in the DC and AC Operating Range table. The device maintains full specification compliance-including 120 ns read access and 10 ms page program-across this entire temperature span, making it suitable for deployment in harsh environments such as factory automation controllers and under-hood automotive modules.

Does the AT29C257-12JI-T require a high-voltage programming supply?

No, the AT29C257-12JI-T operates with a single 5 V ±10% supply for both read and programming functions. All commands-including page program and software chip erase-are executed using standard 5 V logic levels. High-voltage programming (e.g., 12 V) is only required for the obsolete "High Voltage Chip Erase" mode, which is not used in normal operation and is disabled by default. The primary programming path for AT29C257-12JI-T relies entirely on 5 V-only command sequences.

How does software data protection work on the AT29C257-12JI-T?

Software data protection on the AT29C257-12JI-T is enabled via a precise 3-byte command sequence written to specific addresses: 55H to 5555H, AAH to 2AAAH, then 80H to 5555H. Once activated, every subsequent program or erase operation must begin with this same sequence. The protection remains active across power cycles and is disabled only by issuing the reverse unlock sequence (55H→2AAAH, AAH→5555H, F0H→5555H). This mechanism is fully implemented in the AT29C257-12JI-T silicon and verified in the Software Data Protection Enable/Disable Algorithms section.

What package type is used for the AT29C257-12JI-T?

The AT29C257-12JI-T uses a 32-lead Plastic Leaded Chip Carrier (PLCC) package, designated as "32J" in Microchip's ordering information. This surface-mount package features J-bend leads, a square body, and a center power pad (not electrically connected). Its pinout matches industry-standard PLCC-32 footprints, enabling direct compatibility with sockets and PCB layouts designed for AT29C010A and AT29C512 devices.

Can the AT29C257-12JI-T be used as a direct replacement for the AT29C010A?

Yes, the AT29C257-12JI-T is explicitly stated as pin-compatible with the AT29C010A for easy system upgrades. Both devices share identical PLCC-32 packaging, matching pin functions (A0–A14, I/O0–I/O7, CE, OE, WE), and compatible command sets. However, due to its larger 256 Kbit capacity versus the AT29C010A's 1 Mbit, firmware mapping must account for the reduced address space - the AT29C257-12JI-T addresses only 32K words, so upper address lines beyond A14 are unused.