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Microchip Technology AT28HC256-12SU
- Part No.:
- AT28HC256-12SU
- Manufacturer:
- Microchip Technology
- Category:
- Memory
- Package:
- 28-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
AT28HC256-12SU.pdf
- Description:
- IC EEPROM 256KBIT PAR 28SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:4,822
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Product details
Overview
AT28HC256-12SU from Microchip Technology is a 256-Kbit (32,768 × 8) parallel EEPROM with 120 ns read access time, single 5V ±10% supply operation, and industrial temperature range (–40°C to +85°C). It supports page write (1–64 bytes), hardware/software data protection, and DATA Polling for write completion detection - deployed in embedded control firmware storage, industrial PLC configuration memory, and legacy ISA-bus peripheral nonvolatile storage.
For engineers reviewing the AT28HC256-12SU datasheet, AT28HC256-12SU pinout, AT28HC256-12SU application, or AT28HC256-12SU equivalent, key selection considerations include JEDEC byte-wide pin compatibility, 3 mA standby current, 10,000/100,000 write endurance options, and support for 12V chip erase via A9.
Technical Context
The AT28HC256-12SU implements a static RAM-compatible parallel interface with dual-line chip enable (CE) and output enable (OE) control, enabling bus contention avoidance in multi-device systems. Its internal 64-byte page register latches address and data during page writes, decoupling the host bus after initiation.
Write completion is confirmed via I/O7 DATA Polling (complement-to-data toggle) or I/O6 Toggle Bit behavior, both usable at any point during tWC (≤10 ms). Hardware protection includes VCC sense (<3.8 V inhibits write), 5 ms power-on delay, and noise filtering on CE/WE inputs (rejects <15 ns pulses).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory Size | 256 Kbit (32,768 × 8) - supports full firmware image or parameter table storage without external address multiplexing |
| Read Access Time | 120 ns - meets timing requirements for 8 MHz ISA bus and legacy microcontroller interfaces |
| Page Write Cycle | ≤10 ms - enables efficient bulk configuration updates with minimal host CPU blocking |
| Supply Voltage | 5V ±10% - compatible with standard TTL/CMOS logic rails; no auxiliary voltage required |
| Endurance | 10,000 or 100,000 cycles - selectable variant; supports field-updatable calibration data with long service life |
| Data Retention | 10 years - ensures reliable storage of device identity, calibration, or security keys over product lifetime |
| Standby Current | 3 mA - reduces system-level power budget in always-on industrial controllers |
Pinout & Package
AT28HC256-12SU is supplied in a 28-lead SOIC package (suffix 'U'), with JEDEC-standard byte-wide pinout and RoHS-compliant green molding compound.
| 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 chip select; must be low with OE low and WE high for read; initiates write when pulsed low with OE high |
| OE | Output Enable | Active-low output gate; controls tri-state buffer; high during write to prevent bus conflict |
| WE | Write Enable | Active-low write strobe; falling edge latches address/data; high-to-low transition triggers byte or page write |
| VCC | Power Supply | +5V ±10% main supply; powers core logic and I/O buffers; internal VCC sense prevents writes below 3.8 V |
| GND | Ground Reference | Signal and power return; requires low-impedance connection to minimize noise-induced write errors |
Key Features
| Feature | Design Value |
|---|---|
| JEDEC Byte-Wide Pinout | Direct drop-in replacement for industry-standard 27C256/27C512 EPROM sockets without PCB redesign |
| Hardware Data Protection | VCC sense + 5 ms power-on delay + noise filtering eliminates spurious writes during brown-out or EMI events |
| Software Data Protection (SDP) | User-configurable 3-byte unlock sequence (AAh/55h/A0h) prevents accidental writes while allowing field updates |
| 64-Byte Page Register | Reduces host overhead by accepting up to 64 bytes per write command; eliminates 63 separate byte-write cycles |
| 12V Chip Erase | Full-array erase enabled by raising A9 to 12V ±0.5V - useful for factory reprogramming or secure data wipe |
Applications
| Industrial PLC Configuration Storage | Legacy ISA-Bus Peripheral Firmware |
|---|---|
Use Scenario: Storing ladder logic parameters, I/O mapping, and calibration coefficients in programmable logic controllers operating in harsh factory environments. IC Role / Device Role / Timing Role: Nonvolatile configuration memory accessed via parallel bus during boot and runtime; 120 ns read time aligns with 8 MHz ISA timing budgets. Use Value: 10-year data retention and 100,000-cycle endurance ensure reliability across decades of maintenance cycles without backup battery. | Use Scenario: Holding BIOS extension code or device driver microcode in vintage PC add-in cards (e.g., data acquisition boards, motion controllers). IC Role / Device Role / Timing Role: Parallel EEPROM mapped into ISA memory space; JEDEC pinout allows direct socket replacement of obsolete EPROMs. Use Value: No external UV eraser or programming hardware needed; in-system reprogramming via standard ISA bus simplifies field upgrades. |
| Embedded Controller Bootloader Storage | Medical Device Calibration Memory |
Use Scenario: Storing primary bootloader firmware that initializes flash controller and loads application code from external SPI NOR. IC Role / Device Role / Timing Role: First-read memory at reset vector; 120 ns access ensures fast boot sequence with minimal wait states. Use Value: Single 5V supply eliminates need for level shifters or auxiliary regulators; CMOS/TTL compatibility guarantees interoperability with diverse MCU families. | Use Scenario: Retaining sensor offset/gain coefficients and patient-specific settings in portable diagnostic equipment requiring regulatory traceability. IC Role / Device Role / Timing Role: Secure, tamper-resistant parameter store; software data protection prevents unintended overwrite during power transitions. Use Value: Optional 64-byte identification area (7FC0h–7FFFh) supports unique device serialization and audit trail logging. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar parallel EEPROM applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AT28C256-12SU | Same pinout, identical AC/DC specs, but lacks 12V chip erase and optional 64-byte ID area | Suitable for cost-sensitive designs where full-chip erase and device tracking are unnecessary | Select when only basic byte/page write functionality is required and lifecycle management is not mandated |
| MX28F256J3F-12G | 32-pin PLCC package (vs. 28-pin SOIC); 120 ns access; 100,000-cycle endurance; requires 12V for chip erase | Used in legacy telecom line cards with PLCC footprints; not pin-compatible with SOIC-based AT28HC256-12SU | Choose only if existing PCB layout uses 32-lead PLCC; otherwise, SOIC footprint mismatch prevents substitution |
Compared with AT28HC256-12SU, AT28C256-12SU offers identical interface timing but omits critical security and traceability features, while MX28F256J3F-12G provides equivalent endurance and erase capability but demands mechanical redesign due to PLCC packaging.
Availability
AT28HC256-12SU is available at Aetrix Electronics and suitable for industrial PLC configuration storage, legacy ISA-bus peripheral firmware, and embedded controller bootloader storage requiring stable component supply across extended production lifecycles.
Supply support for AT28HC256-12SU 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 a focus on industrial, automotive, and aerospace reliability standards.
The AT28HC256 product line delivers high-speed, pin-compatible EEPROMs designed for legacy system upgrades and industrial control applications where robustness, long-term data retention, and in-system programmability are essential.
FAQ
What is the maximum write cycle time for AT28HC256-12SU during page write operations?
The AT28HC256-12SU has a maximum page write cycle time of 10 ms for standard endurance variants. This value reflects the internal timer duration required to complete programming of up to 64 bytes. The actual time may vary slightly with temperature and supply voltage, but remains bounded by the 10 ms specification under all industrial operating conditions. AT28HC256-12SU supports faster 3 ms writes only in the 'F' variant (e.g., AT28HC256F), which is not applicable to this specific part number.
Does AT28HC256-12SU support both hardware and software data protection mechanisms?
Yes, AT28HC256-12SU integrates dual-layer data protection: hardware protection includes VCC sensing (write inhibition below 3.8 V), 5 ms power-on delay, and CE/WE noise filtering; software protection uses a three-byte unlock sequence (AAh → 55h → A0h) to enable/disable write access. Both mechanisms operate independently and concurrently. AT28HC256-12SU ships with software data protection disabled by default, allowing immediate programming upon power-up.
Can AT28HC256-12SU be used as a direct replacement for older EPROMs like 27C256 in existing designs?
Yes, AT28HC256-12SU features JEDEC-approved byte-wide pinout and operates with identical 5V supply and TTL/CMOS logic levels, making it a functional and pin-compatible replacement for 27C256 EPROMs. Unlike EPROMs, it requires no UV erasure and supports in-system reprogramming. AT28HC256-12SU maintains the same address/data bus timing constraints, eliminating need for wait-state insertion in legacy 8-bit microprocessor systems.
What is the purpose of the 64-byte identification area in AT28HC256-12SU?
The 64-byte identification area (addresses 7FC0h–7FFFh) in AT28HC256-12SU is reserved for user-defined device tracking, serial numbers, calibration history, or firmware version stamps. Access requires raising A9 to 12V ±0.5V, ensuring isolation from normal operation. This area is electrically identical to main array but logically segmented to prevent accidental overwrite during routine parameter updates. AT28HC256-12SU supports full read/write access to this region using standard page write protocols once the 12V condition is met.
How does DATA Polling work on AT28HC256-12SU to indicate write completion?
During a write cycle, AT28HC256-12SU drives I/O7 to the complement of the last written data byte. When the internal programming completes, I/O7 transitions to the true data value - signaling readiness for the next operation. This polling can begin immediately after write initiation and requires no additional control signals. AT28HC256-12SU guarantees valid polling response within the specified tWC (≤10 ms), and the method is fully compatible with interrupt-driven or polled host firmware architectures.
AT28HC256-12SU Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Microchip Technology
- Series:
- -
- Package/Case:
- 28-SOIC (0.295", 7.50mm Width)
- Packaging:
- Tube
- 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:
- 28-SOIC
AT28HC256-12SU FAQ
1.How can I place an order for AT28HC256-12SU through Aetrix?
Please submit a Request for Quotation (RFQ) for AT28HC256-12SU 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 AT28HC256-12SU reliable?
The price and inventory of AT28HC256-12SU are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AT28HC256-12SU is usually 5 days.
3.What payment methods are accepted for AT28HC256-12SU?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AT28HC256-12SU transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AT28HC256-12SU?
AT28HC256-12SU orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AT28HC256-12SU 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 AT28HC256-12SU?
For technical support, including AT28HC256-12SU datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AT28HC256-12SU requirements.
6.How does Aetrix verify that AT28HC256-12SU is sourced from the original manufacturer or authorized distributors?
All AT28HC256-12SU 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 AT28HC256-12SU meets industry standards.
7.What is the process for return or replacement of AT28HC256-12SU?
All AT28HC256-12SU units undergo pre-shipment inspection (PSI). If there is an issue with AT28HC256-12SU, 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 AT28HC256-12SU part is unused and in its original packaging.
Return procedure for AT28HC256-12SU:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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