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Microchip Technology AT28HC256-12PI
- Part No.:
- AT28HC256-12PI
- Manufacturer:
- Microchip Technology
- Category:
- Memory
- Package:
- 28-DIP (0.600", 15.24mm)
- Datasheet:
-
AT28HC256-12PI.pdf
- Description:
- IC EEPROM 256KBIT PARALLEL 28DIP
- Quantity:
- Payment:
- Shipping:
Inventory:4,259
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Product details
Overview
AT28HC256-12PI 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 features 70 ns read access time, 10 ms maximum page write cycle, 5V ±10% single-supply operation, JEDEC-standard 28-pin PDIP pinout, and industrial temperature range (–40°C to +85°C).
For engineers reviewing the AT28HC256-12PI datasheet, AT28HC256-12PI pinout, AT28HC256-12PI application, or AT28HC256-12PI equivalent, key selection criteria include page-write capability (1–64 bytes), DATA Polling/Toggle Bit write completion detection, hardware/software data protection, CMOS/TTL compatibility, and industrial-grade reliability with 10⁴ write cycles and 10-year data retention.
Technical Context
The AT28HC256-12PI operates as a byte- and page-addressable parallel EEPROM with internal address/data latching for up to 64-byte page writes. Its architecture supports Static RAM-like read/write timing without external circuitry, using CE/OE/WE control logic and automatic internal programming timers.
It implements dual write-completion detection (DATA Polling on I/O7 and Toggle Bit on I/O6), VCC-sense write inhibition below 3.8 V, noise-filtered WE/CE inputs, and optional software data protection via three-byte command sequences. The device includes 64 bytes of dedicated identification EEPROM accessible at 7FC0H–7FFFH with A9 = 12 V.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory Size | 256 Kbit (32,768 × 8), organized as byte-wide parallel interface |
| Read Access Time | 120 ns max - defines minimum bus cycle time for reliable read operations |
| Page Write Cycle Time | 10 ms max - determines worst-case latency before next memory access |
| Write Endurance | 10,000 cycles - specifies guaranteed reprogrammability before wear-out |
| Data Retention | 10 years at 85°C - ensures long-term data integrity in industrial environments |
| Supply Voltage | 5 V ±10% - enables direct compatibility with legacy 5V TTL/CMOS logic systems |
| Operating Temperature | –40°C to +85°C - qualified for industrial control, test equipment, and factory automation |
Pinout & Package
AT28HC256-12PI uses a 28-lead plastic dual-inline package (PDIP), 0.600" wide, with JEDEC-standard byte-wide pinout and through-hole mounting.
| 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 data output or write data input |
| CE | Chip Enable | Active-low chip select; disables outputs and inhibits writes when high |
| OE | Output Enable | Active-low control enabling data output during read cycles only |
| WE | Write Enable | Active-low signal initiating byte or page write; latches address/data on falling edge |
| VCC | Power Supply | +5 V ±10% supply pin; powers core logic and memory array |
| GND | Ground Reference | Signal and power return path for all I/O and internal circuitry |
Key Features
| Feature | Design Value |
|---|---|
| 64-byte Page Write | Reduces firmware overhead by allowing burst writes without repeated address setup |
| DATA Polling (I/O7) | Enables real-time write status monitoring without external timing components or polling delays |
| Toggle Bit (I/O6) | Provides hardware-based write completion flag usable in interrupt-driven or low-CPU-load systems |
| Software Data Protection | Prevents accidental writes via user-configurable 3-byte unlock sequence, preserving field-upgrade safety |
| VCC Sense & Noise Filtering | Blocks writes during brown-out or EMI events, eliminating need for external reset supervisors |
Applications
| Industrial PLC Configuration Storage | Medical Device Calibration Data |
|---|---|
Use Scenario: Storing runtime configuration parameters, I/O mapping, and alarm thresholds in programmable logic controllers deployed in factory-floor environments. IC Role / Device Role / Timing Role: Nonvolatile parameter store accessed during boot and runtime; requires robust write endurance and industrial temperature support. Use Value: Enables field-reconfigurable logic without battery-backed SRAM; 10,000-cycle endurance supports decades of maintenance updates. | Use Scenario: Retaining sensor calibration coefficients, patient-specific settings, and regulatory audit logs in portable diagnostic instruments. IC Role / Device Role / Timing Role: Secure, tamper-resistant data vault with software protection and 10-year retention at elevated ambient temperatures. Use Value: Eliminates recalibration drift risk; DATA Polling ensures deterministic firmware update timing during service mode. |
| Avionics Maintenance Log Memory | Test Equipment Firmware Patch Storage |
Use Scenario: Recording flight-hour counters, fault history, and maintenance timestamps in airborne control modules operating across –40°C to +85°C. IC Role / Device Role / Timing Role: High-reliability event logger with write-inhibit safeguards against power interruption during critical logging. Use Value: Hardware VCC-sense and noise filtering prevent partial writes during aircraft power transients. | Use Scenario: Holding field-upgradable firmware patches and instrument calibration scripts in automated test systems requiring zero-downtime updates. IC Role / Device Role / Timing Role: Fast-access patch repository supporting 120 ns reads and 10 ms page writes for rapid reload cycles. Use Value: JEDEC-compatible pinout allows drop-in replacement in legacy 5V test platforms without PCB redesign. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar parallel EEPROM applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AT28C256-12PI | Same 256K × 8 organization and PDIP-28 package; slower 120 ns read access; no software data protection | Lacks SDP and Toggle Bit; suitable only where write safety is managed externally | Select when cost sensitivity outweighs advanced protection features and full feature parity is not required |
| MX28F256J3F-12P | 256K × 8 flash memory; 120 ns read; 10 µs typical byte write; requires sector erase before rewrite | Flash architecture mandates block erasure; incompatible with true EEPROM random-write use cases | Choose only if system firmware already implements flash management; not a functional substitute for EEPROM behavior |
Compared with AT28C256-12PI, the AT28HC256-12PI adds software data protection and Toggle Bit detection-critical for unattended industrial logging-while MX28F256J3F-12P introduces erase-before-write constraints that break direct EEPROM replacement in legacy designs.
Availability
AT28HC256-12PI is available at Aetrix Electronics and suitable for industrial control systems, medical instrumentation, avionics maintenance loggers, and automated test equipment requiring stable component supply and long-term obsolescence support.
Supply support for AT28HC256-12PI 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 support for legacy Atmel parallel EEPROMs including the AT28HC256 family.
The AT28HC256 product line was designed for 5V embedded systems needing reliable, pin-compatible EEPROM replacement of battery-backed SRAM or EPROM, with emphasis on industrial temperature operation and simplified firmware integration.
FAQ
What is the maximum page write size supported by the AT28HC256-12PI?
The AT28HC256-12PI supports page write operations of 1 to 64 bytes per internal programming cycle. All bytes must reside on the same page, defined by identical A6–A14 address bits. Each successive byte must be loaded within 150 µs of the previous one; exceeding this interval triggers automatic internal programming. This capability reduces firmware overhead compared to single-byte writes and is fully implemented in the AT28HC256-12PI silicon.
Does the AT28HC256-12PI require external high-voltage programming circuitry?
No, the AT28HC256-12PI operates from a single 5 V ±10% supply and requires no external high-voltage programming circuitry. All write operations-including byte, page, and chip erase-are executed internally using charge-pump circuitry. The only exception is the optional 64-byte device identification area (7FC0H–7FFFH), which requires 12 V on A9 for access; standard memory operations function entirely at 5 V. This simplifies board design and eliminates HV generator components for the AT28HC256-12PI.
How does software data protection work on the AT28HC256-12PI?
Software data protection (SDP) on the AT28HC256-12PI is enabled by writing three specific bytes (0xAA, 0x55, 0xA0) to addresses 0x5555, 0x2AAA, and 0x5555 respectively. Once activated, all subsequent writes require repeating this sequence before data. SDP remains active across power cycles and is disabled only by a separate 5-byte command. The AT28HC256-12PI ships with SDP disabled, and the feature is fully implemented in its silicon revision.
Can the AT28HC256-12PI be used as a direct replacement for the AT28C256-12PI?
The AT28HC256-12PI is pin-compatible and functionally enhanced relative to the AT28C256-12PI, sharing identical PDIP-28 packaging, JEDEC pinout, and 120 ns read timing. However, it adds software data protection, Toggle Bit detection, and improved write reliability features. While it can replace AT28C256-12PI in most 5V systems, firmware should verify SDP state and leverage enhanced status reporting. The AT28HC256-12PI is not a drop-in replacement if legacy code relies on undocumented AT28C256 timing margins.
What is the purpose of the 64-byte identification EEPROM in the AT28HC256-12PI?
The AT28HC256-12PI includes 64 bytes of dedicated identification EEPROM mapped to addresses 7FC0H–7FFFH. Access requires raising A9 to 12 V ±0.5 V; otherwise, these locations are masked. This area is intended for storing unique device identifiers, calibration constants, manufacturing lot codes, or firmware version stamps-separate from main memory to avoid interference during normal operation. Its existence and addressing scheme are confirmed in the AT28HC256-12PI datasheet and apply specifically to this variant.
AT28HC256-12PI Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Microchip Technology
- Series:
- -
- Package/Case:
- 28-DIP (0.600", 15.24mm)
- 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:
- Through Hole
- Supplier Device Package:
- 28-PDIP
AT28HC256-12PI FAQ
1.How can I place an order for AT28HC256-12PI through Aetrix?
Please submit a Request for Quotation (RFQ) for AT28HC256-12PI 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 AT28HC256-12PI reliable?
The price and inventory of AT28HC256-12PI are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AT28HC256-12PI is usually 5 days.
3.What payment methods are accepted for AT28HC256-12PI?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AT28HC256-12PI transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AT28HC256-12PI?
AT28HC256-12PI orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AT28HC256-12PI 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 AT28HC256-12PI?
For technical support, including AT28HC256-12PI datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AT28HC256-12PI requirements.
6.How does Aetrix verify that AT28HC256-12PI is sourced from the original manufacturer or authorized distributors?
All AT28HC256-12PI 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 AT28HC256-12PI meets industry standards.
7.What is the process for return or replacement of AT28HC256-12PI?
All AT28HC256-12PI units undergo pre-shipment inspection (PSI). If there is an issue with AT28HC256-12PI, 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 AT28HC256-12PI part is unused and in its original packaging.
Return procedure for AT28HC256-12PI:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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