Microchip Technology AT25256-10PC

Overview

AT25256-10PC from Atmel (now Microchip) is a 256-Kbit SPI serial EEPROM organized as 32,768 × 8-bit words, operating from 2.7V to 5.5V, featuring 3 MHz clock rate, 64-byte page write capability, and hardware/software write protection via WP and HOLD pins. It serves as nonvolatile configuration storage in microcontroller-based industrial control modules requiring robust data retention.

For engineers reviewing the AT25256-10PC datasheet, AT25256-10PC pinout, AT25256-10PC application, or AT25256-10PC equivalent, key selection criteria include its 2.7–5.5V supply range, 5 ms typical write cycle time, block write protection granularity (1/4, 1/2, or full array), and EIAJ SOIC-8 package compatibility with legacy PCB footprints.

Technical Context

The AT25256-10PC implements a synchronous SPI slave interface compliant with Modes 0 (CPOL=0, CPHA=0) and 3 (CPOL=1, CPHA=1), using separate SI (input) and SO (output) lines for full-duplex communication. Its internal architecture includes an 8-bit instruction register, nonvolatile status register (BP0/BP1/WPEN bits), and automatic address incrementing during sequential reads/writes.

Write operations require explicit WREN instruction prior to WRITE or WRSR commands; during active write cycles, only RDSR is accepted. Block protection is enforced by status register bits BP1/BP0, enabling selective lock of top quarter (0x6000–0x7FFF), top half (0x4000–0x7FFF), or entire memory array (0x0000–0x7FFF) on the AT25256-10PC.

Key Specifications

Pinout & Package

AT25256-10PC is housed in an 8-pin EIAJ SOIC (Small Outline Integrated Circuit) package, 0.200" wide, with standard 1.27 mm pitch and gull-wing leads. Pin 1 is marked by a notch or dot; the package is RoHS-compliant and rated for industrial temperature range (−40°C to +85°C).

Key Features

Applications

Equivalent & Alternatives

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

Compared with M95256-WDW6TP and BR25L256FJ-WE2, the AT25256-10PC offers proven industrial temperature stability and Atmel's legacy design-in support, while trading off speed for broader voltage margin and simpler qualification path in legacy systems.

Availability

AT25256-10PC is available at Aetrix Electronics and suitable for industrial control systems, medical instrumentation, automotive body electronics, and smart metering applications requiring stable component supply and long-term obsolescence management.

Supply support for AT25256-10PC 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 semiconductor manufacturer specializing in microcontrollers, nonvolatile memory, and secure authentication ICs.

The AT25xxx family was designed specifically for SPI-based embedded systems needing reliable, low-power, pin-efficient nonvolatile storage-targeting industrial, automotive, and medical applications where data integrity and long-term retention are mandatory.

FAQ

What is the maximum clock frequency supported by the AT25256-10PC?

The AT25256-10PC supports a maximum SCK clock frequency of 3 MHz across its full 2.7V–5.5V supply range and −40°C to +85°C operating temperature. This value is specified in the AC Characteristics table under fSCK and applies to both read and write operations. Exceeding this limit may cause data corruption or command rejection. The AT25256-10PC does not support higher speeds even at elevated VCC or reduced temperature.

Does the AT25256-10PC require a separate erase command before writing?

No, the AT25256-10PC does not require a separate erase command. All write operations-including byte and page writes-are self-timed and internally erase the target memory location before programming. The device automatically handles erase-and-program sequencing upon receipt of a valid WRITE instruction after WREN. This simplifies firmware implementation and eliminates risk of partial-erase failures. The AT25256-10PC completes each write in 5 ms typical time.

How does the WP pin function on the AT25256-10PC?

The WP (Write Protect) pin on the AT25256-10PC provides hardware-level protection for the status register only when the WPEN bit is set to "1". When WP is low and WPEN=1, all WRSR commands are blocked-even if WREN has been issued. If WPEN=0, the WP pin has no effect. The AT25256-10PC allows status register writes only when WP is high or WPEN=0, enabling flexible system-level protection schemes.

Can the AT25256-10PC be used in SPI Mode 1 or Mode 2?

No, the AT25256-10PC is explicitly specified for SPI Modes 0 (CPOL=0, CPHA=0) and 3 (CPOL=1, CPHA=1) only. It does not support Mode 1 (CPOL=0, CPHA=1) or Mode 2 (CPOL=1, CPHA=0). Attempting to use unsupported modes will result in incorrect data sampling or command interpretation. The AT25256-10PC's timing diagrams and functional description confirm compatibility solely with Mode 0 and Mode 3 clocking conventions.

What memory address range is protected when BP1=1 and BP0=0 on the AT25256-10PC?

When BP1=1 and BP0=0 in the status register of the AT25256-10PC, the top half of the memory array is protected-specifically addresses 0x4000 to 0x7FFF (16,384 bytes). This corresponds to the "2(1/2)" protection level defined in Table 4 of the datasheet. Read operations remain unrestricted, but WRITE and WRSR commands targeting this region are ignored. The AT25256-10PC enforces this protection regardless of WP pin state when WPEN=1.