Microchip Technology AT28C256-15PU

Overview

AT28C256-15PU from Microchip Technology is an industrial-grade 256-Kbit paged parallel EEPROM organized as 32,768 × 8, featuring 150 ns read access time, 3–10 ms page write cycle, and single 5V ±10% supply operation. It supports hardware/software data protection and DATA Polling for write completion detection, deployed in legacy industrial controllers and embedded firmware storage where byte-level nonvolatility and SRAM-like interface are required.

For engineers reviewing the AT28C256-15PU datasheet, AT28C256-15PU pinout, AT28C256-15PU application, or AT28C256-15PU equivalent, key selection considerations include JEDEC-compliant 28-pin PDIP package compatibility, 64-byte page write capability, CMOS/TTL I/O compatibility, industrial temperature range (−40°C to +85°C), and software data protection enable/disable sequences.

Technical Context

The AT28C256-15PU implements a paged write architecture with internal 64-byte latches and autonomous control timer, enabling up to 64 bytes per write cycle without external timing control. Its dual-line chip enable (CE) and output enable (OE) logic allows bus contention avoidance in shared-memory systems.

It integrates VCC sense (write inhibit below 3.8 V), 5 ms power-on delay, noise filtering on WE/CE (<15 ns pulses rejected), and toggle-bit (I/O6) or DATA Polling (I/O7 complement) for real-time write status monitoring - all operating within a single 5V supply and JEDEC-standard byte-wide pinout.

Key Specifications

Pinout & Package

AT28C256-15PU is supplied in a 28-lead plastic dual in-line package (PDIP) with JEDEC-standard byte-wide pinout and 0.6-inch body width. Pin 1 is marked by a notch or dot; pins are arranged in two rows with address/data multiplexing eliminated - all signals are dedicated and electrically isolated per function.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AT28C256-15PU, the PLCC variant offers better thermal dissipation and SMT compatibility but demands PCB redesign, while the SOIC variant preserves full pin-for-pin and timing equivalence - making it the only true mechanical substitute without layout impact.

Availability

AT28C256-15PU is available at Aetrix Electronics and suitable for industrial PLC firmware storage, medical device calibration data retention, and legacy test equipment memory upgrades requiring stable component supply and long-term obsolescence management.

Supply support for AT28C256-15PU 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 devices, and nonvolatile memory solutions, with ISO 9001-certified manufacturing and broad industrial qualification.

The AT28C256 product line delivers cost-effective, pin-compatible EEPROM replacements for legacy EPROM/SRAM sockets in industrial, medical, and automotive systems - emphasizing reliability, long-term supply, and backward compatibility over feature expansion.

FAQ

What is the maximum page write size supported by the AT28C256-15PU?

The AT28C256-15PU supports a maximum page write size of 64 bytes. This is enabled by its internal 64-byte page register, which latches address and data simultaneously. Each byte in the page must be loaded within 150 µs of the prior byte (tBLC), and all addresses must reside on the same page defined by A6–A14. The AT28C256-15PU does not support larger or variable-page configurations - the 64-byte limit is fixed in silicon.

Does the AT28C256-15PU require a 12V supply for any operation?

The AT28C256-15PU operates exclusively from a single 5V ±10% supply for normal read/write operations. A 12V ±0.5V supply is required only for optional chip erase mode (applied to A9) and is not needed for standard page or byte writes, DATA Polling, or software data protection. The AT28C256-15PU includes internal VCC sensing that inhibits writes below 3.8V, eliminating external high-voltage circuitry in most applications.

How does DATA Polling work on the AT28C256-15PU, and which pin is used?

DATA Polling on the AT28C256-15PU uses I/O7: during a write cycle, reading the last written address returns the complement of the written data on I/O7; once the write completes, true data appears. This allows microcontrollers to poll I/O7 without timers or external hardware. The AT28C256-15PU guarantees this behavior across its full industrial temperature range and supports polling at any point during tWC - no setup delay is required before initiating the first poll.

Is the AT28C256-15PU pin-compatible with the 27C256 EPROM?

Yes - the AT28C256-15PU uses a JEDEC-approved byte-wide pinout identical to the 27C256 EPROM, including matching A0–A14, I/O0–I/O7, CE, OE, WE, VCC, and GND assignments. No signal inversion or external logic is needed. However, the AT28C256-15PU requires no UV erasure, supports in-system writes, and features active-low WE instead of the 27C256's programming pulse - making it a functional and mechanical drop-in replacement for firmware upgrades.

What endurance rating applies to the AT28C256-15PU, and how is it marked?

The AT28C256-15PU carries a standard endurance rating of 10,000 write/erase cycles, indicated by absence of an "E" or "F" suffix in its top-side marking (e.g., "AT28C256-" without trailing letter). Extended (100,000-cycle) and Fast Write (3 ms) variants are marked "AT28C256E" and "AT28C256F", respectively. The AT28C256-15PU's 10K rating is validated per JEDEC standards and applies across its full −40°C to +85°C operating range.