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Microchip Technology AT28HC256E-12SI
- Part No.:
- AT28HC256E-12SI
- Manufacturer:
- Microchip Technology
- Category:
- Memory
- Package:
- 28-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
AT28HC256E-12SI.pdf
- Description:
- IC EEPROM 256KBIT PAR 28SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:3,559
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Product details
Overview
AT28HC256E-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 70 ns read access time, supports 64-byte page writes with ≤10 ms internal write cycle time, and operates across industrial temperature range (−40°C to +85°C) on single 5V ±10% supply.
For engineers reviewing the AT28HC256E-12SI datasheet, AT28HC256E-12SI pinout, AT28HC256E-12SI application, or AT28HC256E-12SI equivalent, this page provides verified technical context, JEDEC-compliant pin mapping, endurance and timing specifications, hardware/software data protection mechanisms, and real-world use cases in legacy industrial controllers and firmware update modules.
Technical Context
The AT28HC256E-12SI implements a CMOS-based parallel EEPROM architecture with internal address/data latching for page write operations and dual end-of-write detection via DATA Polling (I/O7 complement) and Toggle Bit (I/O6 toggling). Its JEDEC-standard 28-pin SOIC package supports byte- and page-level writes without external timing components.
It integrates VCC sense, power-on delay, noise filtering, and software data protection (SDP) to prevent inadvertent writes during power transitions. The device includes 64 bytes of dedicated identification EEPROM accessible at 7FC0H–7FFFH using A9 = 12V.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory Size | 256 Kbit (32,768 × 8), organized as byte-addressable parallel array |
| Read Access Time | 120 ns max - defines minimum bus cycle duration for reliable read operations |
| Page Write Cycle Time | ≤10 ms - maximum internal programming time for up to 64 bytes per page |
| Endurance | 100,000 write/erase cycles - validated lifetime for high-reliability firmware storage |
| Data Retention | 10 years at 85°C - guaranteed data integrity under industrial thermal stress |
| Supply Voltage | 5V ±10% - compatible with legacy 5V TTL/CMOS logic families without level shifting |
| Operating Temperature | −40°C to +85°C - qualified for industrial-grade embedded environments |
Pinout & Package
AT28HC256E-12SI is supplied in a 28-lead, 0.300" wide plastic gull-wing small outline (SOIC) package (package code 28S), compliant with JEDEC MS-013 and RoHS/Green (Pb/halide-free) requirements.
| 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 | Bi-directional Data Bus | 8-bit parallel interface for read/write data transfer; TTL/CMOS compatible |
| CE | Chip Enable | Active-low chip select; must be low for any memory access |
| OE | Output Enable | Active-low control for output buffer; enables data read when CE and OE low, WE high |
| WE | Write Enable | Active-low signal initiating byte or page write; latches address/data on falling edge |
| VCC | Power Supply | +5V ±10% main supply; powers core logic and I/O buffers |
| GND | Ground Reference | Signal and power return path; required for stable operation and noise immunity |
Key Features
| Feature | Design Value |
|---|---|
| 64-byte Page Write | Reduces firmware update time by up to 64× vs. byte writes; eliminates external address sequencing logic |
| DATA Polling (I/O7) | Enables real-time write completion detection without polling timers or interrupts |
| Toggle Bit (I/O6) | Provides hardware-based asynchronous write status monitoring independent of data content |
| Software Data Protection (SDP) | Prevents accidental writes via 3-byte unlock sequence; remains active through power cycles |
| 12V Device Identification Area | 64-byte dedicated EEPROM region (7FC0H–7FFFH) for serialization, calibration, or revision tracking |
Applications
| Industrial PLC Firmware Storage | Legacy Medical Instrument Calibration Data |
|---|---|
Use Scenario: Storing boot firmware and configuration parameters in programmable logic controllers deployed in factory automation environments. IC Role / Device Role / Timing Role: Nonvolatile parallel memory providing direct CPU bus access for fast firmware execution and field-upgradable parameter tables. Use Value: 100K endurance and 10-year data retention ensure reliability over extended maintenance intervals without battery backup. | Use Scenario: Holding calibrated sensor offsets and diagnostic thresholds in Class II medical devices requiring traceable, tamper-resistant data storage. IC Role / Device Role / Timing Role: Secure, write-protected EEPROM for critical calibration constants accessed during power-up self-test sequences. Use Value: Hardware VCC-sense and SDP prevent corruption during brown-out conditions or unintended host writes. |
| Avionics Maintenance Log Buffer | Automotive ECU Bootloader Configuration |
Use Scenario: Recording flight-hour counters, fault logs, and maintenance timestamps in certified avionics subsystems operating across −40°C to +85°C. IC Role / Device Role / Timing Role: Industrial-temperature EEPROM interfaced to microcontroller via standard parallel bus for deterministic log writes. Use Value: Page write capability enables efficient batch logging; 120 ns read timing supports real-time log retrieval during diagnostics. | Use Scenario: Storing bootloader version, secure boot keys, and flash partition maps in automotive engine control units with strict ASIL-B compliance requirements. IC Role / Device Role / Timing Role: Trusted nonvolatile memory holding immutable bootloader metadata, protected by hardware write inhibit and SDP. Use Value: Dual write-detection (DATA Polling + Toggle Bit) ensures robust firmware update verification before handoff to application code. |
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 | 10K endurance (vs. 100K), 10 ms write time, same pinout and voltage | Suitable only for infrequent configuration updates; not recommended for high-cycle firmware patching | Select AT28HC256E-12SI when >10K write cycles or long-term field reliability is required. |
| MX28F256J3F-12SI | JEDEC-compatible 28-pin SOIC, 256 Kbit, but requires 12V VPP for programming; no built-in SDP | Lacks integrated software protection and automatic page write; needs external high-voltage generation | Choose AT28HC256E-12SI for simplified 5V-only design and enhanced data integrity features. |
Compared with AT28C256-12SI and MX28F256J3F-12SI, the AT28HC256E-12SI delivers 10× higher endurance, eliminates need for external 12V programming circuitry, and embeds both hardware and software write safeguards-making it optimal for field-upgradable industrial firmware storage where long service life and data security are critical.
Availability
AT28HC256E-12SI is available at Aetrix Electronics and suitable for industrial PLCs, medical instrumentation, avionics loggers, and automotive ECUs requiring stable component supply with full lifecycle support.
Supply support for AT28HC256E-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, qualification, and manufacturing continuity for the AT28HC256 family.
The AT28HC256 series was designed for legacy 5V parallel bus systems requiring high-reliability, field-programmable nonvolatile storage with minimal external components and industrial temperature operation.
FAQ
What is the maximum write cycle time for AT28HC256E-12SI during a 64-byte page write?
The AT28HC256E-12SI has a maximum page write cycle time of 10 ms, as specified in its AC characteristics table. This value applies to the full 64-byte page operation and reflects the internal timer-controlled programming duration. The device automatically completes the write without external timing control once the page load sequence ends, and end-of-write status can be confirmed via DATA Polling on I/O7 or Toggle Bit on I/O6. This timing is consistent across all operating temperatures for the -12 speed grade.
Does AT28HC256E-12SI require a 12V programming voltage?
No, the AT28HC256E-12SI operates with a single 5V ±10% supply for both read and write functions. Unlike older EPROMs or some flash variants, it does not require external 12V VPP. However, 12V is needed only for accessing the optional 64-byte device identification area (7FC0H–7FFFH) via A9, which is separate from normal memory operations. All standard reads, byte writes, and page writes function fully at 5V.
How does Software Data Protection (SDP) work on AT28HC256E-12SI?
SDP on the AT28HC256E-12SI is enabled by writing a precise three-byte sequence (0xAA → 0x55 → 0xA0) to addresses 0x5555, 0x2AAA, and 0x5555 respectively. Once activated, all subsequent writes require repeating this sequence before data. SDP persists through power cycles and remains active until explicitly disabled using a different unlock sequence. The AT28HC256E-12SI ships with SDP disabled, and the feature is fully implemented in silicon without external components.
Is AT28HC256E-12SI pin-compatible with AT28HC256-12SI?
Yes, AT28HC256E-12SI is pin-compatible with AT28HC256-12SI and shares identical 28-pin SOIC (28S) packaging, JEDEC byte-wide pinout, and electrical interface. The "E" suffix denotes the high-endurance variant (100K cycles vs. 10K), while all timing, voltage, and functional behavior-including CE/OE/WE control, page write, and polling-remain identical. No PCB or firmware changes are required for drop-in replacement.
What industrial temperature range does AT28HC256E-12SI support?
The AT28HC256E-12SI is rated for operation from −40°C to +85°C, meeting industrial temperature specifications. This range is confirmed in the Ordering Information section (27.1) and DC/AC Operating Range table (Section 5), where "SI" explicitly denotes the Industrial temperature grade. The device undergoes full characterization and screening across this range for parameters including tACC (120 ns max), ICC (80 mA active), and ISB (3 mA standby).
AT28HC256E-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
AT28HC256E-12SI FAQ
1.How can I place an order for AT28HC256E-12SI through Aetrix?
Please submit a Request for Quotation (RFQ) for AT28HC256E-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 AT28HC256E-12SI reliable?
The price and inventory of AT28HC256E-12SI are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AT28HC256E-12SI is usually 5 days.
3.What payment methods are accepted for AT28HC256E-12SI?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AT28HC256E-12SI transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AT28HC256E-12SI?
AT28HC256E-12SI orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AT28HC256E-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 AT28HC256E-12SI?
For technical support, including AT28HC256E-12SI datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AT28HC256E-12SI requirements.
6.How does Aetrix verify that AT28HC256E-12SI is sourced from the original manufacturer or authorized distributors?
All AT28HC256E-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 AT28HC256E-12SI meets industry standards.
7.What is the process for return or replacement of AT28HC256E-12SI?
All AT28HC256E-12SI units undergo pre-shipment inspection (PSI). If there is an issue with AT28HC256E-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 AT28HC256E-12SI part is unused and in its original packaging.
Return procedure for AT28HC256E-12SI:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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