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Microchip Technology AT28HC256-12PC
- Part No.:
- AT28HC256-12PC
- Manufacturer:
- Microchip Technology
- Category:
- Memory
- Package:
- 28-DIP (0.600", 15.24mm)
- Datasheet:
-
AT28HC256-12PC.pdf
- Description:
- IC EEPROM 256KBIT PARALLEL 28DIP
- Quantity:
- Payment:
- Shipping:
Inventory:2,776
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Product details
Overview
AT28HC256-12PC from Atmel is a 256 Kbit (32K × 8) parallel EEPROM IC with JEDEC-standard byte-wide pinout, 120 ns maximum read access time, 3–10 ms page write cycle, and single 5V ±10% supply. It supports hardware/software data protection, DATA polling, and toggle-bit write completion detection for embedded control and firmware storage in industrial instrumentation.
For engineers reviewing the AT28HC256-12PC datasheet, AT28HC256-12PC pinout, AT28HC256-12PC application, or AT28HC256-12PC equivalent, key selection considerations include its 120 ns read timing, 64-byte page write capability, CMOS/TTL compatibility, industrial temperature range (−40°C to +85°C), and PDIP-28 packaging with JEDEC-compliant pin assignment.
Technical Context
The AT28HC256-12PC operates as a drop-in parallel memory replacement for SRAM in legacy systems, requiring no external timing components. 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 is verified via I/O7 DATA polling (complement-to-data signaling) or I/O6 toggle-bit behavior-both usable at any point during tWC. Hardware write inhibition includes VCC sense (<3.8 V), 5 ms power-on delay, and noise filtering on WE/CE inputs.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory Size | 256 Kbit (32,768 × 8), organized as byte-addressable nonvolatile storage |
| Read Access Time | 120 ns max - defines minimum bus cycle time for reliable read operation |
| Page Write Cycle | 3–10 ms max - determines firmware update latency per 64-byte block |
| Supply Voltage | 5 V ±10% - compatible with legacy 5V logic rails without level shifting |
| Operating Temp | −40°C to +85°C - qualified for industrial environments with thermal cycling |
| Endurance | 10,000 write cycles - specifies maximum reprogramming count before wear-out |
| Data Retention | 10 years at 85°C - guarantees stored firmware integrity over product lifetime |
Pinout & Package
AT28HC256-12PC uses a 28-lead plastic dual in-line package (PDIP-28), 0.600" wide, with JEDEC-standard byte-wide pinout and through-hole mounting. Pin 1 is marked by notch or dot; pins 1 and 17 are NC in PLCC variants but not applicable here.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| A0–A14 | Address Inputs | 15-bit address bus selecting one of 32,768 bytes; A6–A14 define page boundaries for 64-byte writes |
| I/O0–I/O7 | Bidirectional Data Bus | 8-bit parallel interface for read/write; supports true bidirectional data flow without direction control pin |
| CE | Chip Enable | Active-low chip select; must be low with OE low and WE high for read access |
| OE | Output Enable | Active-low output gate; controls data bus tristate to prevent contention during shared-bus operation |
| WE | Write Enable | Active-low write strobe; falling edge latches address/data; initiates byte or page write sequence |
| VCC, GND | Power Supply | Single 5V supply with decoupling required near VCC pin; ground reference for all signals |
Key Features
| Feature | Design Value |
|---|---|
| 64-byte Page Write | Reduces firmware update time by up to 64× vs. byte-write mode; requires ≤150 µs between successive bytes |
| DATA Polling (I/O7) | Enables real-time write status monitoring without dedicated status registers or interrupts |
| Software Data Protection | Three-byte unlock sequence prevents accidental writes; remains active across power cycles until explicitly disabled |
| Hardware Write Inhibit | VCC sense, 5 ms power-on delay, and 15 ns noise filtering eliminate spurious writes during brownout or EMI events |
| Extra 64-byte ID EEPROM | Dedicated memory region (7FC0H–7FFFH) accessible at 12V on A9 for device serialization or calibration data storage |
Applications
| Industrial PLC Firmware Storage | Medical Device Configuration Memory |
|---|---|
Use Scenario: Storing ladder logic programs and I/O mapping tables in programmable logic controllers subject to frequent field updates. IC Role / Device Role / Timing Role: Nonvolatile parallel memory providing direct CPU bus access with deterministic 120 ns read timing and page-write efficiency. Use Value: Enables in-system firmware upgrades without removing the module; 10,000-cycle endurance supports multi-year maintenance cycles. | Use Scenario: Holding calibrated sensor offsets, user preferences, and safety-critical configuration parameters in portable diagnostic equipment. IC Role / Device Role / Timing Role: Trusted configuration store with software/hardware write protection ensuring parameter integrity during power transitions. Use Value: Prevents corruption of life-support settings via SDP lock; 10-year data retention meets FDA Class II device lifecycle requirements. |
| Avionics Control Panel Memory | Test Equipment Calibration Storage |
Use Scenario: Retaining flight control mode presets and pilot-configurable thresholds in certified cockpit displays operating across −40°C to +85°C. IC Role / Device Role / Timing Role: Industrial-temperature-rated EEPROM interfacing directly to microcontroller address/data buses with no glue logic. Use Value: Eliminates need for external voltage translators or regulators; JEDEC pinout ensures drop-in compatibility with legacy designs. | Use Scenario: Storing factory-calibrated ADC/DAC coefficients and linearity correction tables in benchtop multimeters and signal generators. IC Role / Device Role / Timing Role: High-reliability nonvolatile memory supporting infrequent but critical write operations with DATA polling confirmation. Use Value: Guarantees calibration accuracy over 10 years; 120 ns read speed enables fast coefficient lookup during measurement processing. |
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 pinout and timing, but lacks software data protection and extra 64-byte ID area; 10K endurance only | Suitable for cost-sensitive, non-critical firmware storage where write protection is handled externally | Select when SDP and device ID features are unnecessary and BOM cost reduction is prioritized |
| MX28F256J3F-12PC | 32-pin PLCC, 120 ns access, 100K endurance, but requires 12V VPP for programming; no DATA polling | Used in military/aerospace systems requiring extended endurance and MIL-STD-883 screening | Choose for high-reliability programs needing >10K cycles and formal qualification, accepting larger footprint and higher programming voltage |
Compared with AT28HC256-12PC, AT28C256-12PC offers identical timing and packaging but omits software protection and ID memory, while MX28F256J3F-12PC trades ease of use for higher endurance and formal screening-making AT28HC256-12PC optimal for industrial firmware with integrated security and compact PDIP layout.
Availability
AT28HC256-12PC is available at Aetrix Electronics and suitable for industrial PLC firmware storage, medical device configuration memory, avionics control panel memory, and test equipment calibration storage requiring stable component supply and long-term obsolescence management.
Supply support for AT28HC256-12PC 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
Atmel Corporation (now part of Microchip Technology) is a semiconductor manufacturer specializing in microcontrollers, nonvolatile memory, and secure authentication devices.
The AT28HC256 product line was designed for legacy system upgrades and industrial control applications requiring pin-compatible, 5V-only parallel EEPROM with robust write protection and JEDEC-standard interfaces.
FAQ
What is the maximum read access time specified for the AT28HC256-12PC?
The AT28HC256-12PC has a maximum read access time of 120 ns, measured from address valid or CE/OE assertion to valid data on I/O0–I/O7. This value is guaranteed across the full industrial temperature range (−40°C to +85°C) and 5V ±10% supply, enabling integration into systems with tight memory timing budgets without wait-state insertion.
Does the AT28HC256-12PC support page write operations, and what is the maximum page size?
Yes, the AT28HC256-12PC supports page write operations with a fixed page size of 64 bytes. The device latches up to 64 bytes internally using its page register, allowing sequential writes within 150 µs intervals. This reduces total programming time significantly compared to byte-by-byte writes and is controlled entirely by the host's WE/CE timing without external logic.
How does hardware write protection work on the AT28HC256-12PC?
Hardware write protection on the AT28HC256-12PC includes four mechanisms: (1) VCC sense disabling writes below ~3.8 V, (2) automatic 5 ms power-on delay before write enable, (3) write inhibition if OE is low or CE/WE are in invalid states, and (4) 15 ns noise filtering on WE/CE inputs. These features prevent corruption during power-up, brownout, or EMI events without software intervention.
Can the AT28HC256-12PC be used in place of standard SRAM in existing designs?
Yes, the AT28HC256-12PC is accessed like Static RAM for reads and writes-no external timing components or address latches are needed. Its JEDEC-standard pinout, CMOS/TTL compatibility, and identical control signal behavior (CE/OE/WE) allow direct substitution in many SRAM-based systems, provided write timing and data retention requirements align with EEPROM characteristics.
What package type is used for the AT28HC256-12PC, and is it RoHS compliant?
The AT28HC256-12PC uses a 28-lead plastic dual in-line package (PDIP-28), 0.600" wide, with through-hole mounting. Per Atmel documentation, this variant is offered in both standard and green (Pb/halide-free) versions; the "-12PC" suffix denotes the standard PDIP package, and RoHS compliance depends on date code and ordering option-confirm with Aetrix Electronics' lot-specific certification.
AT28HC256-12PC 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:
- 0°C ~ 70°C (TC)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 28-PDIP
AT28HC256-12PC FAQ
1.How can I place an order for AT28HC256-12PC through Aetrix?
Please submit a Request for Quotation (RFQ) for AT28HC256-12PC 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 AT28HC256-12PC reliable?
The price and inventory of AT28HC256-12PC are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AT28HC256-12PC is usually 5 days.
3.What payment methods are accepted for AT28HC256-12PC?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AT28HC256-12PC transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AT28HC256-12PC?
AT28HC256-12PC orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AT28HC256-12PC 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 AT28HC256-12PC?
For technical support, including AT28HC256-12PC datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AT28HC256-12PC requirements.
6.How does Aetrix verify that AT28HC256-12PC is sourced from the original manufacturer or authorized distributors?
All AT28HC256-12PC 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 AT28HC256-12PC meets industry standards.
7.What is the process for return or replacement of AT28HC256-12PC?
All AT28HC256-12PC units undergo pre-shipment inspection (PSI). If there is an issue with AT28HC256-12PC, 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 AT28HC256-12PC part is unused and in its original packaging.
Return procedure for AT28HC256-12PC:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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