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Microchip Technology AT28HC256-12JU-T
- Part No.:
- AT28HC256-12JU-T
- Manufacturer:
- Microchip Technology
- Category:
- Memory
- Package:
- 32-LCC (J-Lead)
- Datasheet:
-
AT28HC256-12JU-T.pdf
- Description:
- IC EEPROM 256KBIT PAR 32PLCC
- Quantity:
- Payment:
- Shipping:
Inventory:2,642
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Product details
Overview
AT28HC256-12JU-T from Microchip Technology is a 256-Kbit (32,768 × 8) parallel EEPROM with 120 ns read access time, single 5V ±10% supply, and industrial temperature range (–40°C to +85°C). It supports 1–64-byte page writes with up to 10 ms internal write cycle time, hardware/software data protection, and DATA Polling for end-of-write detection. Used in embedded control firmware storage, configuration memory, and boot code retention where nonvolatile byte-level rewrite capability is required.
For engineers reviewing the AT28HC256-12JU-T datasheet, AT28HC256-12JU-T pinout, AT28HC256-12JU-T application, or AT28HC256-12JU-T equivalent, this page delivers verified electrical specs, JEDEC-compliant byte-wide pin mapping, endurance and retention metrics, and real-world use context for industrial system design and BOM continuity planning.
Technical Context
The AT28HC256-12JU-T implements a CMOS-based parallel EEPROM architecture with integrated address/data latching for page write operations. Its internal control timer manages autonomous 64-byte programming without external timing circuitry, and it uses dual-line chip enable (CE) and output enable (OE) logic to prevent bus contention during mixed read/write cycles.
It features both DATA Polling (I/O7 complement toggle) and Toggle Bit (I/O6 state alternation) mechanisms for asynchronous write completion detection. Hardware write inhibition includes VCC sense (<3.8 V), 5 ms power-on delay, and noise filtering on WE/CE inputs - all active without software intervention.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory Size | 256 Kbit (32,768 × 8), enabling full firmware image or multi-parameter configuration storage in compact footprint |
| Read Access Time | 120 ns max - meets timing requirements for 8-bit microcontroller interfaces operating at ≤8 MHz |
| Page Write Cycle Time | 10 ms max - enables efficient bulk parameter updates without CPU polling overhead |
| Endurance | 10,000 write/erase cycles - sufficient for field-updatable calibration tables or infrequent configuration changes |
| Data Retention | 10 years at +85°C - ensures long-term reliability in unattended industrial equipment |
| Supply Voltage | 5V ±10% - compatible with legacy 5V logic systems without level-shifting |
| Operating Temperature | –40°C to +85°C - qualified for industrial control cabinets and outdoor telemetry enclosures |
Pinout & Package
AT28HC256-12JU-T is packaged in a 32-lead PLCC (Plastic Leaded Chip Carrier) with JEDEC-standard byte-wide pinout. Pin 1 and Pin 17 are designated "Don't Connect" per datasheet; all other pins follow industry-standard address/data/control mapping for drop-in compatibility with legacy parallel memory designs.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| A0–A14 | Address Inputs | 15-bit address bus supporting full 32K-word addressing; A6–A14 define page boundaries for 64-byte writes |
| I/O0–I/O7 | Bidirectional Data Bus | CMOS/TTL-compatible 8-bit data path; I/O7 used for DATA Polling, I/O6 for Toggle Bit status reporting |
| CE | Chip Enable | Active-low device selection; must be low with OE low and WE high for read access |
| OE | Output Enable | Active-low output gating; controls high-impedance state to prevent bus contention |
| WE | Write Enable | Active-low write strobe; falling edge latches address/data; initiates byte or page programming |
| VCC | Power Supply | +5V ±10% main supply; powers core logic and I/O buffers |
| GND | Ground Reference | Signal and power return path; requires low-impedance PCB connection for stable read/write margins |
Key Features
| Feature | Design Value |
|---|---|
| Automatic Page Write | Internal 64-byte latch eliminates external address sequencing logic and reduces MCU GPIO overhead during bulk writes |
| DATA Polling & Toggle Bit | Dual asynchronous write completion detection methods allow flexible polling strategy without dedicated interrupt lines |
| Hardware Write Inhibit | VCC sense, 5 ms power-on delay, and 15 ns noise filtering prevent spurious writes during brown-out or EMI events |
| Software Data Protection | User-configurable 3-byte unlock sequence prevents accidental overwrites of critical configuration or calibration data |
| Device Identification Area | 64-byte reserved EEPROM segment (7FC0H–7FFFH) accessible via 12V A9 bias for unique unit serialization or traceability |
Applications
| Industrial PLC Configuration Storage | Medical Device Calibration Memory |
|---|---|
Use Scenario: Storing I/O mapping, PID tuning parameters, and alarm thresholds in programmable logic controllers deployed in factory automation environments. IC Role / Device Role / Timing Role: Nonvolatile configuration register bank accessed via 8-bit parallel bus during startup and runtime reconfiguration. Use Value: Enables field-upgradable settings without requiring flash reprogramming or firmware reload; 10-year retention ensures parameter integrity across maintenance cycles. | Use Scenario: Holding sensor calibration coefficients and safety-critical operational limits in portable diagnostic instruments subject to regulatory audit. IC Role / Device Role / Timing Role: Secure, tamper-resistant parameter vault with software lockout preventing unauthorized modification during device servicing. Use Value: Meets IEC 62304 traceability requirements via 64-byte ID area; hardware write inhibit guarantees data integrity during power interruption. |
| Telecom Base Station Bootloader Storage | Automotive Body Control Module EEPROM |
Use Scenario: Storing bootloader code and secure boot keys in remote radio units operating in wide-temperature outdoor enclosures. IC Role / Device Role / Timing Role: Parallel-boot memory mapped into microcontroller address space for fast initialization prior to FPGA configuration. Use Value: 120 ns access time supports deterministic boot timing; industrial temp rating ensures reliability at –40°C cold start. | Use Scenario: Retaining seat position, mirror angle, and lighting preferences across ignition cycles in automotive interior control modules. IC Role / Device Role / Timing Role: Low-power configuration scratchpad accessed during wake-up sequences using CE/OE-controlled burst reads. Use Value: 3 mA standby current minimizes battery drain during vehicle sleep mode; 5V compatibility avoids need for additional LDOs. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar parallel EEPROM applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AT28C256-12JU | Same 256-Kbit organization and 120 ns speed grade, but lacks software data protection and device ID area | Suitable for cost-sensitive applications where write protection is handled externally | Select when simplified firmware and lower unit cost outweigh need for on-chip security features |
| FM24CL256-G | F-RAM with 10¹⁴ endurance and 150 ns access, but requires I²C interface and 2.7–3.6 V supply | Used where frequent parameter updates demand near-infinite write cycles, not parallel bus compatibility | Choose only if migrating to serial interface and accepting voltage rail change; not a pin-compatible substitute |
Compared with AT28HC256-12JU-T, AT28C256-12JU offers identical timing and packaging but omits software lock and ID memory - reducing cost while sacrificing configurability. FM24CL256-G provides vastly higher endurance but mandates interface and power architecture redesign, making it unsuitable for direct replacement in existing 5V parallel designs.
Availability
AT28HC256-12JU-T is available at Aetrix Electronics and suitable for industrial control systems, medical instrumentation, telecom infrastructure, and automotive body electronics requiring stable component supply and long-term lifecycle support.
Supply support for AT28HC256-12JU-T 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 is a global semiconductor company specializing in microcontrollers, analog devices, and nonvolatile memory solutions, with emphasis on industrial, automotive, and aerospace reliability standards.
The AT28HC256 product line delivers high-speed parallel EEPROMs optimized for legacy 5V system upgrades and applications demanding byte-erasable, long-retention configuration storage without flash programming complexity.
FAQ
What is the maximum write cycle time for AT28HC256-12JU-T during a 64-byte page write operation?
The AT28HC256-12JU-T has a maximum page write cycle time of 10 ms, as specified in the datasheet for standard endurance grade devices. This internal timer operates autonomously after the final byte is latched, freeing the host bus for other tasks. The 10 ms value applies specifically to the AT28HC256-12JU-T variant marked with "12" (120 ns access) and standard endurance (10,000 cycles), not the "F" (3 ms) or "E" (100,000 cycles) variants.
Does AT28HC256-12JU-T support both hardware and software write protection?
Yes, AT28HC256-12JU-T implements dual-layer write protection. Hardware protection includes VCC sensing (<3.8 V), 5 ms power-on delay, and 15 ns noise filtering on WE/CE inputs. Software Data Protection (SDP) is enabled via a documented 3-byte unlock sequence (AAh→55h→A0h to addresses 5555h/2AAAh/5555h), which must precede any protected write. AT28HC256-12JU-T ships with SDP disabled by default.
Can AT28HC256-12JU-T be used in place of older AT28C256 devices without circuit modifications?
AT28HC256-12JU-T is pin-compatible and functionally supersets AT28C256 in 32-lead PLCC packages, sharing identical JEDEC byte-wide pinout, 5V supply, and AC/DC timing specifications. However, AT28HC256-12JU-T adds software data protection and a 64-byte device ID area - features that remain inactive unless explicitly enabled, ensuring backward compatibility in existing AT28C256 designs.
What is the purpose of the 64-byte device identification area in AT28HC256-12JU-T?
The 64-byte device identification area (addresses 7FC0H–7FFFH) in AT28HC256-12JU-T is reserved for user-defined serialization, calibration traceability, or manufacturing lot tracking. Access requires raising A9 to 12V ±0.5V during read/write operations. This feature enables unit-level data logging without consuming main memory space, supporting ISO 13485 and IEC 62304 compliance in regulated medical and industrial systems.
How does DATA Polling work on AT28HC256-12JU-T to detect write completion?
During a write cycle, AT28HC256-12JU-T outputs the complement of the last written data byte on I/O7. When the internal programming completes, I/O7 transitions to true data - signaling readiness for the next access. This polling mechanism requires no additional control lines and works concurrently with other bus activity, allowing the host MCU to verify completion without fixed delays or interrupts. It is fully supported in both byte and page write modes.
AT28HC256-12JU-T Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Microchip Technology
- Series:
- -
- Package/Case:
- 32-LCC (J-Lead)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- 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:
- 32-PLCC (11.43x13.97)
AT28HC256-12JU-T FAQ
1.How can I place an order for AT28HC256-12JU-T through Aetrix?
Please submit a Request for Quotation (RFQ) for AT28HC256-12JU-T 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 AT28HC256-12JU-T reliable?
The price and inventory of AT28HC256-12JU-T are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AT28HC256-12JU-T is usually 5 days.
3.What payment methods are accepted for AT28HC256-12JU-T?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AT28HC256-12JU-T transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AT28HC256-12JU-T?
AT28HC256-12JU-T orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AT28HC256-12JU-T 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 AT28HC256-12JU-T?
For technical support, including AT28HC256-12JU-T datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AT28HC256-12JU-T requirements.
6.How does Aetrix verify that AT28HC256-12JU-T is sourced from the original manufacturer or authorized distributors?
All AT28HC256-12JU-T 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 AT28HC256-12JU-T meets industry standards.
7.What is the process for return or replacement of AT28HC256-12JU-T?
All AT28HC256-12JU-T units undergo pre-shipment inspection (PSI). If there is an issue with AT28HC256-12JU-T, 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 AT28HC256-12JU-T part is unused and in its original packaging.
Return procedure for AT28HC256-12JU-T:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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