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Microchip Technology AT28HC256-12SI
- Part No.:
- AT28HC256-12SI
- Manufacturer:
- Microchip Technology
- Category:
- Memory
- Package:
- 28-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
AT28HC256-12SI.pdf
- Description:
- IC EEPROM 256KBIT PAR 28SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:4,518
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Product details
Overview
AT28HC256-12SI from Microchip Technology (formerly Atmel) is a 256 Kbit (32K × 8) parallel EEPROM IC used for nonvolatile program/data storage in embedded control and instrumentation systems. It delivers 120 ns read access time, supports 1–64-byte page writes with internal latching, operates from a single 5V ±10% supply, and is rated for industrial temperature range (−40°C to +85°C) in SOIC package.
For engineers reviewing the AT28HC256-12SI datasheet, AT28HC256-12SI pinout, AT28HC256-12SI application, or AT28HC256-12SI equivalent, this page provides verified functional specifications, JEDEC-compliant byte-wide interface details, hardware/software write protection mechanisms, DATA polling and toggle-bit write completion detection, and industrial-grade reliability metrics including 10⁴ write cycles and 10-year data retention.
Technical Context
The AT28HC256-12SI implements a CMOS-based parallel EEPROM architecture with internal address/data latches enabling 64-byte page write operations without external timing logic. Its dual-line chip enable (CE) and output enable (OE) control allows flexible bus contention management during read cycles.
Write operation relies on an internal control timer and supports both byte and page modes, with software data protection (SDP) activated via a three-byte command sequence. End-of-write detection is implemented via I/O7 DATA polling or I/O6 toggle-bit functionality - both accessible without halting system operation.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory Size | 256 Kbit (32,768 × 8), organized as byte-addressable nonvolatile storage |
| Read Access Time | 120 ns maximum - determines minimum CPU wait-state duration for reliable read access |
| Page Write Cycle Time | 10 ms maximum - defines worst-case latency before next memory access can begin |
| Endurance | 10,000 write/erase cycles - specifies guaranteed reprogrammability before wear-out |
| Data Retention | 10 years at +85°C - ensures long-term validity of stored configuration or calibration data |
| Supply Voltage | 5 V ±10% - compatible with standard TTL/CMOS logic rails without regulation overhead |
| Operating Temperature | −40°C to +85°C - validated for industrial environments including factory automation and power metering |
Pinout & Package
AT28HC256-12SI is supplied in a 28-lead, 0.300" wide plastic gull-wing small outline integrated circuit (SOIC) package per JEDEC MS-013, with 28-pin JEDEC-standard byte-wide parallel interface.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| A0–A14 | Address Inputs | 15-bit address bus selecting one of 32,768 memory locations |
| I/O0–I/O7 | Bidirectional Data Bus | 8-bit parallel interface for read/write data transfer; high-impedance when disabled |
| CE | Chip Enable | Active-low signal enabling device selection; required low for all read/write operations |
| OE | Output Enable | Active-low control for output buffer; must be low during read, high during write |
| WE | Write Enable | Active-low strobe initiating byte or page write; falling edge latches address/data |
| VCC | Power Supply | +5 V ±10% main supply; powers core logic and I/O buffers |
| GND | Ground Reference | Common return path for all internal circuits and I/O signals |
Key Features
| Feature | Design Value |
|---|---|
| JEDEC Byte-Wide Pinout | Ensures drop-in compatibility with legacy SRAM and EPROM sockets in existing PCB layouts |
| Internal 64-Byte Page Register | Enables burst programming of up to 64 bytes without repeated address setup, reducing firmware overhead |
| Hardware Write Inhibit | VCC sense and noise filtering prevent spurious writes during power-up/down or EMI events |
| Software Data Protection (SDP) | User-configurable lock requiring 3-byte command sequence before any write - prevents accidental firmware corruption |
| DATA Polling & Toggle Bit | Real-time write status monitoring via I/O7 complement or I/O6 toggling - eliminates need for fixed delay timers |
Applications
| Industrial PLC Configuration Storage | Medical Device Calibration Data |
|---|---|
Use Scenario: Storing I/O mapping tables and runtime parameters in programmable logic controllers deployed in factory-floor environments. IC Role / Device Role / Timing Role: Nonvolatile configuration memory accessed during boot and runtime via parallel bus; requires 120 ns read timing compliance. Use Value: Enables field-upgradable logic configurations without battery-backed SRAM; 10-year retention guarantees parameter integrity across maintenance cycles. | Use Scenario: Holding sensor calibration coefficients and safety-critical operational limits in portable diagnostic equipment. IC Role / Device Role / Timing Role: Secure, tamper-resistant data storage with software write protection to prevent unauthorized modification of medical settings. Use Value: SDP feature blocks unintended writes during hot-plug events or firmware updates, ensuring regulatory compliance with IEC 62304. |
| Automotive Body Control Module | Test Equipment Firmware Patch Storage |
Use Scenario: Retaining user preferences (e.g., mirror position, seat memory) and fault logs in 12V automotive body control units. IC Role / Device Role / Timing Role: Industrial-temperature EEPROM interfaced directly to microcontroller GPIOs; withstands −40°C cold cranking and +85°C under-hood conditions. Use Value: Use Value: 10,000-cycle endurance supports frequent log updates over 15-year vehicle lifetime; green (Pb/halide-free) packaging meets AEC-Q200 material requirements. | Use Scenario: Hosting field-installable firmware patches for automated test equipment where full flash reprogramming is impractical. IC Role / Device Role / Timing Role: Parallel-accessible patch memory mapped into microcontroller address space; leverages page write to minimize update time. Use Value: 10 ms max page write enables sub-100ms patch application; DATA polling allows deterministic synchronization without interrupt latency penalties. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar parallel EEPROM applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AT28C256-12SI | Same pinout and timing, but lacks software data protection (SDP) and internal page register; only supports byte writes | No SDP means no firmware-level write lock; unsuitable where accidental overwrite risk is unacceptable | Select only if cost sensitivity outweighs security and page-write efficiency needs |
| M95256-DW | Serial SPI interface (not parallel); 5V-tolerant I/O; 5 ms typical write cycle; same 256 Kbit density | Requires SPI controller instead of parallel bus; lower pin count but higher software overhead for block transfers | Prefer for space-constrained designs where board real estate or routing complexity favors serial interface |
Compared with AT28C256-12SI, the AT28HC256-12SI adds page write capability and software data protection - critical for robust field updates - while M95256-DW trades parallel speed and simplicity for reduced footprint and SPI compatibility, making it suitable for new designs prioritizing integration over legacy bus reuse.
Availability
AT28HC256-12SI is available at Aetrix Electronics and suitable for industrial control systems, medical instrumentation, automotive body electronics, and test equipment requiring stable component supply with guaranteed long-term availability and traceable sourcing.
Supply support for AT28HC256-12SI 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 product support, documentation, and manufacturing continuity for the AT28HC256 family.
The AT28HC256 series was designed as a drop-in replacement for battery-backed SRAM and UV-erasable EPROM in industrial and automotive applications requiring reliable, low-power, single-supply nonvolatile storage with fast read access and flexible write control.
FAQ
What is the maximum page write size supported by the AT28HC256-12SI?
The AT28HC256-12SI supports page write operations of 1 to 64 bytes per internal programming cycle. The device includes an internal 64-byte page register that latches address and data automatically, allowing burst programming without external address sequencing. This capability reduces firmware execution time and bus arbitration overhead compared to byte-by-byte writes - a key advantage in real-time embedded systems using the AT28HC256-12SI.
Does the AT28HC256-12SI require external high-voltage programming circuitry?
No, the AT28HC256-12SI performs all write and erase operations using only the standard 5V ±10% supply - no external 12V or higher voltage is needed. Unlike older EPROMs, it uses on-chip charge pumps for internal high-voltage generation. The optional 12V on A9 is exclusively for accessing the 64-byte device identification area (7FC0H–7FFFH), not for normal memory programming - standard operation of the AT28HC256-12SI remains fully 5V-compatible.
How does the software data protection (SDP) feature work on the AT28HC256-12SI?
The AT28HC256-12SI implements software data protection (SDP) via a three-byte unlock sequence written to specific addresses (5555H, 2AAAH, then 5555H with data A0H) to enable protection, and a separate five-byte disable sequence to deactivate it. Once enabled, all subsequent writes require repeating the unlock sequence first. SDP persists through power cycles and protects against accidental writes during brownout or reset - a critical safeguard for firmware and calibration data stored in the AT28HC256-12SI.
Can the AT28HC256-12SI be used as a direct replacement for SRAM in existing designs?
Yes - the AT28HC256-12SI is accessed like a static RAM for reads and writes, with identical CE/OE/WE control timing and JEDEC-standard byte-wide pinout. It requires no external components for basic operation. However, write cycles introduce latency (up to 10 ms), so designs must implement DATA polling or toggle-bit checking instead of assuming immediate write completion - unlike true SRAM. This behavior is fully documented in the AT28HC256-12SI datasheet and supported in legacy systems with minor firmware adaptation.
What package type and lead finish does the AT28HC256-12SI use?
The AT28HC256-12SI is packaged in a 28-lead, 0.300" wide plastic gull-wing small outline (SOIC) package designated as 28S per Atmel's ordering guide. It features Pb/halide-free (green) finish compliant with RoHS Directive 2011/65/EU and J-STD-609A Class 1 marking. The package meets JEDEC MS-013 standards and is rated for industrial temperature operation (−40°C to +85°C), making it suitable for deployment in the AT28HC256-12SI's target applications.
AT28HC256-12SI Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Microchip Technology
- Series:
- -
- Package/Case:
- 28-SOIC (0.295", 7.50mm Width)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Programmable:
- Not Verified
- Memory Type:
- Non-Volatile
- Memory Format:
- EEPROM
- Technology:
- EEPROM
- Memory Size:
- 256Kbit
- Memory Organization:
- 32K x 8
- Memory Interface:
- Parallel
- Clock Frequency:
- -
- Write Cycle Time - Word, Page:
- 10ms
- Access Time:
- 120 ns
- Voltage - Supply:
- 4.5V ~ 5.5V
- Operating Temperature:
- -40°C ~ 85°C (TC)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 28-SOIC
AT28HC256-12SI FAQ
1.How can I place an order for AT28HC256-12SI through Aetrix?
Please submit a Request for Quotation (RFQ) for AT28HC256-12SI 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 AT28HC256-12SI reliable?
The price and inventory of AT28HC256-12SI are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AT28HC256-12SI is usually 5 days.
3.What payment methods are accepted for AT28HC256-12SI?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AT28HC256-12SI transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AT28HC256-12SI?
AT28HC256-12SI orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AT28HC256-12SI 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 AT28HC256-12SI?
For technical support, including AT28HC256-12SI datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AT28HC256-12SI requirements.
6.How does Aetrix verify that AT28HC256-12SI is sourced from the original manufacturer or authorized distributors?
All AT28HC256-12SI 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 AT28HC256-12SI meets industry standards.
7.What is the process for return or replacement of AT28HC256-12SI?
All AT28HC256-12SI units undergo pre-shipment inspection (PSI). If there is an issue with AT28HC256-12SI, 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 AT28HC256-12SI part is unused and in its original packaging.
Return procedure for AT28HC256-12SI:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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