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Microchip Technology AT28HC256-12SC
- Part No.:
- AT28HC256-12SC
- Manufacturer:
- Microchip Technology
- Category:
- Memory
- Package:
- 28-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
AT28HC256-12SC.pdf
- Description:
- IC EEPROM 256KBIT PAR 28SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:3,900
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Product details
Overview
AT28HC256-12SC from Microchip Technology (formerly Atmel) is a 256 Kbit (32K × 8) parallel EEPROM with JEDEC-standard byte-wide pinout, 120 ns maximum access time, single 5V ±10% supply, and industrial temperature range (–40°C to +85°C). It supports automatic page write (1–64 bytes), DATA polling, and hardware/software data protection for embedded firmware storage and configuration retention in legacy microcontroller systems.
For engineers reviewing the AT28HC256-12SC datasheet, AT28HC256-12SC pinout, AT28HC256-12SC application, or AT28HC256-12SC equivalent, key selection criteria include its 120 ns read timing, 3–10 ms page write cycle, CMOS/TTL compatibility, 28-pin SOIC package, and support for software-controlled write protection and device identification EEPROM.
Technical Context
The AT28HC256-12SC operates as a drop-in parallel memory replacement for SRAM or EPROM in legacy 8-bit bus architectures, requiring no external timing logic. Its internal 64-byte page register latches address and data during write cycles, freeing the bus for concurrent operations while an internal control timer manages programming.
Write completion detection is implemented via dual methods: DATA polling on I/O7 (complement-to-data toggle) and I/O6 toggle bit monitoring. Hardware write inhibition includes VCC sense (<3.8 V), 5 ms power-on delay, noise filtering (<15 ns pulses rejected), and CE/OE/WE state locking.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory Size | 256 Kbit (32,768 × 8), organized as byte-addressable nonvolatile storage |
| Access Time | 120 ns max - defines minimum bus cycle duration for reliable read access in 8-bit systems |
| Page Write Cycle | 3 ms or 10 ms max - determines firmware update latency; F-version = 3 ms, standard = 10 ms |
| Endurance | 10,000 write/erase cycles - sets field-replaceable configuration lifetime under frequent updates |
| Data Retention | 10 years at 85°C - guarantees long-term validity of stored calibration or serial data without refresh |
| Supply Voltage | 5 V ±10% - compatible with legacy TTL/CMOS logic rails without regulation overhead |
| Operating Temp | –40°C to +85°C - qualified for industrial control, instrumentation, and automotive under-hood modules |
Pinout & Package
AT28HC256-12SC is supplied in a 28-lead, 0.300" wide plastic gull-wing small outline (SOIC) package (package code "S"), 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 supporting full 32K-word addressing; A6–A14 define page boundaries for 64-byte writes |
| I/O0–I/O7 | Bi-directional Data Bus | 8-bit parallel interface; supports true read/write data transfer without direction control pins |
| CE | Chip Enable | Active-low chip select; must be low with OE low and WE high for valid read access |
| OE | Output Enable | Active-low output gate; controls data bus drive to prevent contention when multiple devices share bus |
| WE | Write Enable | Active-low write strobe; falling edge latches address; rising edge latches data for byte/page write |
| VCC, GND | Power Supply | Single 5V supply with <5 mA standby current; decoupling required within 1 cm of pins per JEDEC guidelines |
Key Features
| Feature | Design Value |
|---|---|
| Automatic Page Write | Enables burst programming of up to 64 bytes in one internal cycle, reducing host CPU overhead vs. byte-by-byte writes |
| DATA Polling & Toggle Bit | Dual asynchronous write-complete detection methods eliminate need for fixed delays or external timers in host firmware |
| Hardware Write Inhibit | VCC sensing, power-on delay, and noise filtering prevent spurious writes during brown-out or EMI events |
| Software Data Protection | User-configurable 3-byte unlock sequence prevents accidental writes without modifying hardware design or layout |
| Device Identification Area | 64-byte dedicated EEPROM region (7FC0H–7FFFH) accessible at 12 V for serialization or calibration data storage |
Applications
| Industrial PLC Configuration Storage | Legacy Embedded System Bootloader Memory |
|---|---|
Use Scenario: Storing user-defined I/O mapping, PID tuning parameters, and alarm thresholds in programmable logic controllers operating in harsh factory environments. IC Role / Device Role / Timing Role: Nonvolatile configuration memory accessed via 8-bit parallel bus during system initialization and runtime parameter updates. Use Value: 10-year data retention at 85°C ensures parameter integrity across maintenance cycles without battery backup. | Use Scenario: Holding boot firmware images and recovery code for 8051- or Z80-based medical instruments where flash upgrade paths are unavailable. IC Role / Device Role / Timing Role: Parallel boot memory mapped into CPU address space; 120 ns access enables direct execution from bus without wait states. Use Value: JEDEC-standard pinout allows direct replacement of obsolete EPROMs without PCB redesign. |
| Automotive Body Control Module Calibration | Test Equipment Self-Test Data Log |
Use Scenario: Recording sensor offset corrections and actuator learning values in automotive BCMs subjected to thermal cycling and vibration. IC Role / Device Role / Timing Role: EEPROM storage for field-updatable calibration tables accessed by microcontroller over parallel bus during power-up. Use Value: Industrial temperature rating (–40°C to +85°C) and 10K endurance meet AEC-Q100 stress requirements for under-dash modules. | Use Scenario: Capturing pass/fail results and measurement timestamps during automated functional testing of PCB assemblies. IC Role / Device Role / Timing Role: Local nonvolatile log buffer enabling test sequencer to record outcomes without host PC dependency. Use Value: Page write capability (1–64 bytes) minimizes write time per test step, increasing throughput vs. byte-write-only alternatives. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar parallel EEPROM applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AT28C256-12PC | Same 256 Kbit capacity and 120 ns speed, but in 28-pin PDIP package; no Green option; 10K endurance only | Through-hole mounting for prototyping or legacy board rework; lacks SOIC footprint compatibility | Select for hand-soldered development boards or socket-based systems where SOIC reflow is impractical |
| MN5Q2568B-12 | 256 Kbit parallel EEPROM, 120 ns access, 28-pin SOIC, but rated only for commercial temp (0°C to 70°C); no software data protection | Limited to benign environments like lab equipment; lacks SDP and toggle-bit detection features | Choose only if industrial temp rating and write safety features are not required and cost is primary driver |
Compared with AT28HC256-12PC and MN5Q2568B-12, the AT28HC256-12SC uniquely combines industrial temperature operation, Green packaging, software data protection, and dual write-completion detection-making it the only option qualified for ruggedized, field-upgradable embedded systems requiring long-term reliability.
Availability
AT28HC256-12SC is available at Aetrix Electronics and suitable for industrial PLCs, legacy bootloader systems, automotive body control modules, and automated test equipment requiring stable component supply across extended product lifecycles.
Supply support for AT28HC256-12SC 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 the AT28HC256 family, including datasheets, errata, and long-term manufacturing commitments.
The AT28HC256 product line was designed for pin-compatible replacement of UV-erasable EPROMs and battery-backed SRAM in 8-bit microcontroller systems, emphasizing reliability, ease of integration, and backward compatibility.
FAQ
What is the maximum access time specified for the AT28HC256-12SC?
The AT28HC256-12SC has a maximum address-to-output access time (tACC) of 120 ns, as indicated by the "12" suffix in its part number. This value is guaranteed across the full industrial temperature range (–40°C to +85°C) and defines the minimum clock period required for reliable read operations in synchronous bus designs.
Does the AT28HC256-12SC support page write operations, and what is the maximum page size?
Yes, the AT28HC256-12SC supports page write operations with a maximum size of 64 bytes. The device uses an internal 64-byte page register to latch address and data; all bytes in a page write must reside on the same page defined by A6–A14, and successive bytes must be loaded within 150 µs to avoid premature write initiation.
How does hardware write protection function on the AT28HC256-12SC?
Hardware write protection on the AT28HC256-12SC includes four mechanisms: (1) VCC sense disabling writes below ~3.8 V, (2) 5 ms power-on delay before write enable, (3) requirement that CE low, OE high, and WE low simultaneously for write initiation, and (4) rejection of input pulses shorter than 15 ns on CE or WE pins to suppress noise-induced writes.
Can the AT28HC256-12SC be used as a direct replacement for older EPROMs like the 27C256?
Yes, the AT28HC256-12SC is pin-compatible with the 27C256 EPROM in 28-pin SOIC packages and shares identical address/data bus connections and JEDEC-standard pinout. However, unlike UV-erasable EPROMs, the AT28HC256-12SC supports in-system electrical erasure and does not require a UV eraser or programming voltage beyond 5 V.
What is the purpose of the additional 64-byte EEPROM area in the AT28HC256-12SC?
The additional 64-byte EEPROM area (addresses 7FC0H–7FFFH) in the AT28HC256-12SC is reserved for device-specific data such as serial numbers, calibration coefficients, or manufacturing lot codes. Access requires raising A9 to 12 V ±0.5 V, and reads/writes follow the same timing as main array operations.
AT28HC256-12SC 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:
- 0°C ~ 70°C (TC)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 28-SOIC
AT28HC256-12SC FAQ
1.How can I place an order for AT28HC256-12SC through Aetrix?
Please submit a Request for Quotation (RFQ) for AT28HC256-12SC 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 AT28HC256-12SC reliable?
The price and inventory of AT28HC256-12SC are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AT28HC256-12SC is usually 5 days.
3.What payment methods are accepted for AT28HC256-12SC?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AT28HC256-12SC transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AT28HC256-12SC?
AT28HC256-12SC orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AT28HC256-12SC 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 AT28HC256-12SC?
For technical support, including AT28HC256-12SC datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AT28HC256-12SC requirements.
6.How does Aetrix verify that AT28HC256-12SC is sourced from the original manufacturer or authorized distributors?
All AT28HC256-12SC 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 AT28HC256-12SC meets industry standards.
7.What is the process for return or replacement of AT28HC256-12SC?
All AT28HC256-12SC units undergo pre-shipment inspection (PSI). If there is an issue with AT28HC256-12SC, 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 AT28HC256-12SC part is unused and in its original packaging.
Return procedure for AT28HC256-12SC:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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