Microchip Technology AT29C256-70PI

Overview

AT29C256-70PI from Atmel is a 256 Kbit (32K × 8) 5V-only Flash memory IC designed for in-system reprogrammability in embedded controllers and firmware storage applications. It delivers 70 ns read access time, supports page programming of 64-byte blocks with 10 ms internal erase-and-program cycle, and operates across industrial temperature range (–40°C to +85°C) with CMOS/TTL-compatible I/O.

For engineers reviewing the AT29C256-70PI datasheet, AT29C256-70PI pinout, AT29C256-70PI application, or AT29C256-70PI equivalent, key selection criteria include its 5V-only operation, hardware/software data protection, DATA polling and toggle-bit program status detection, and compatibility with legacy 28-pin PDIP footprints in industrial control and boot code storage designs.

Technical Context

The AT29C256-70PI implements a nonvolatile Flash architecture with internal address/data latches for 64-byte page loading, automatic internal erase-and-program sequencing controlled by an on-chip timer, and dual-line chip enable (CE) and output enable (OE) for bus contention management. Its read interface emulates static RAM timing behavior.

Programming requires no external high-voltage supply: all operations-including page program, chip erase, and software data protection enable/disable-are executed via 5V-only command sequences applied to standard address/data/control pins. Data integrity is enforced through VCC sense (≥3.8 V), noise filtering (<15 ns pulse rejection), and write inhibit logic (OE low, CE high, or WE high).

Key Specifications

Pinout & Package

AT29C256-70PI is supplied in a 28-lead plastic dual inline package (PDIP), 0.600" wide (28P6), with 0.100" lead pitch and through-hole mounting. Pin 1 is marked with a notch or dot; pins 1 and 28 are VCC and GND respectively.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AT29C256-70PI, AT29C256-70JI offers identical functionality in a surface-mount PLCC package ideal for automated assembly, while MX29LV256EITI-70G provides modern 3.3 V efficiency and CFI compliance at the cost of 5 V system compatibility and pinout change - making AT29C256-70PI optimal for drop-in replacement in existing 5 V industrial PDIP layouts.

Availability

AT29C256-70PI is available at Aetrix Electronics and suitable for industrial PLC firmware storage, legacy microcontroller boot memory, and embedded system configuration storage requiring stable component supply across extended product lifecycles.

Supply support for AT29C256-70PI 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

Atmel Corporation (now part of Microchip Technology) is a U.S.-based semiconductor company specializing in microcontrollers, Flash memory, and secure authentication devices.

The AT29C256 product line was engineered for 5V-only in-system programmability in industrial and automotive control systems, emphasizing robustness, ease of integration, and long-term reliability in legacy 8-bit architectures.

FAQ

What is the maximum operating frequency supported by the AT29C256-70PI?

The AT29C256-70PI does not operate at a clock frequency like a microcontroller. Instead, its AC timing is defined by access times: it guarantees a maximum 70 ns address-to-output delay (tACC) and 70 ns CE-to-output delay (tCE) under 5 V ±10% supply and industrial temperature conditions. These values correspond to effective bus speeds up to ~14 MHz in static-memory-mapped systems, assuming proper setup/hold timing margins are maintained for address and control signals.

Does the AT29C256-70PI require external high-voltage programming circuitry?

No, the AT29C256-70PI does not require external high-voltage programming circuitry. It is a 5-volt-only Flash memory: all programming, erasure, and data protection operations are performed using standard 5 V logic levels applied to CE, OE, WE, address, and data pins. Internal circuitry handles voltage boosting and timing, eliminating the need for 12 V supplies or dedicated programmers - enabling true in-system reprogramming.

How is program completion detected on the AT29C256-70PI?

Program completion on the AT29C256-70PI is detected using two hardware-supported methods: DATA polling and the toggle bit. During programming, reading the last loaded byte returns the complement of data on I/O7 (DATA polling), reverting to true data upon completion. Alternatively, I/O6 toggles between 0 and 1 during active programming and stabilizes when complete. Both methods allow polling using standard read cycles without external hardware or interrupts.

What package type is used for the AT29C256-70PI?

The AT29C256-70PI uses a 28-lead plastic dual inline package (PDIP), 0.600" wide (designated 28P6 in Atmel documentation). It features through-hole mounting with 0.100" lead pitch, pin 1 identified by a notch or dot, and mechanical dimensions conforming to JEDEC MS-011, Variation AB. This package is compatible with legacy sockets and wave-solder processes common in industrial electronics manufacturing.

Can the AT29C256-70PI be used as a direct replacement for EPROMs like the 27C256?

Yes, the AT29C256-70PI can functionally replace UV-erasable EPROMs such as the 27C256 in many designs, but with important distinctions: it uses electrical erasure (no UV window or eraser needed), supports in-system programming, and requires specific 5V-only command sequences for write operations. While pinout and read timing are compatible, write control differs - OE must be high during programming, and software data protection may require initialization. The AT29C256-70PI retains the same 28-pin DIP footprint and address/data bus structure.