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Microchip Technology AT28HC256-90PI
- Part No.:
- AT28HC256-90PI
- Manufacturer:
- Microchip Technology
- Category:
- Memory
- Package:
- 28-DIP (0.600", 15.24mm)
- Datasheet:
-
AT28HC256-90PI.pdf
- Description:
- IC EEPROM 256KBIT PARALLEL 28DIP
- Quantity:
- Payment:
- Shipping:
Inventory:1,456
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Product details
Overview
AT28HC256-90PI from Atmel is a 256 Kbit (32K × 8) parallel EEPROM IC designed for nonvolatile data storage in embedded systems requiring byte- and page-level reprogrammability. It delivers 90 ns read access time, supports 1–64-byte page writes with ≤3 ms or ≤10 ms cycle time, operates on single 5V ±10% supply, and features hardware/software write protection. It is commonly used in industrial control firmware storage and configuration memory where field-upgradable persistent data retention is critical.
For engineers reviewing the AT28HC256-90PI datasheet, AT28HC256-90PI pinout, AT28HC256-90PI application, or AT28HC256-90PI equivalent, key selection considerations include JEDEC-standard 28-pin PDIP package compatibility, industrial temperature range (−40°C to +85°C), 10⁴/10⁵ endurance cycles, DATA polling/toggle-bit write completion detection, and software data protection enable/disable sequences.
Technical Context
The AT28HC256-90PI implements a CMOS-based parallel EEPROM architecture with internal 64-byte page latches and autonomous internal control timer for self-timed write operations. Its dual-line chip enable (CE) and output enable (OE) logic enables bus contention avoidance in shared-memory systems, while address/data bus release during page write allows concurrent host operations.
It integrates VCC sense circuitry (write inhibit below 3.8 V), noise filtering on WE/CE inputs (<15 ns pulse rejection), and optional 12 V A9-based device identification EEPROM. The software data protection mechanism requires a precise three-byte command sequence to enable/disable, and remains active across power cycles without external intervention.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory Size | 256 Kbit (32,768 × 8 bits); sufficient for boot code, calibration tables, or parameter sets in resource-constrained controllers. |
| Read Access Time | 90 ns max; compatible with 10 MHz Z80, 8051, and 68K-based systems without wait states. |
| Page Write Cycle Time | 3 ms or 10 ms max; determines minimum latency between successive 64-byte firmware updates. |
| Endurance | 10⁴ or 10⁵ write/erase cycles; defines usable lifetime in logging or configuration update applications. |
| Data Retention | 10 years at 85°C; ensures long-term validity of stored settings in unpowered industrial equipment. |
| Supply Voltage | 5 V ±10%; eliminates need for dedicated voltage regulators in legacy 5 V logic systems. |
| Operating Temperature | −40°C to +85°C; certified for deployment in industrial automation, motor drives, and outdoor instrumentation. |
Pinout & Package
AT28HC256-90PI uses a 28-lead plastic dual in-line package (PDIP), 0.600" wide (28P6), with JEDEC-standard byte-wide pinout and through-hole mounting. Pin 1 is index-marked; 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 supporting full 32K-word addressing; A0–A5 select bytes within 64-byte page during page write. |
| I/O0–I/O7 | Bidirectional Data Bus | CMOS/TTL-compatible 8-bit data path; supports true read/write without external transceivers. |
| CE | Chip Enable | Active-low global device select; combined with OE/WE controls read/write mode and prevents bus contention. |
| OE | Output Enable | Active-low output gate; high-Z state when deasserted isolates data bus during CPU fetch or write cycles. |
| WE | Write Enable | Active-low write strobe; falling edge latches address/data; rising edge initiates internal programming timer. |
| VCC, GND | Power Supply | Single 5 V supply with <3 mA standby current; low-power operation extends battery life in backup memory applications. |
Key Features
| Feature | Design Value |
|---|---|
| Automatic Page Write | Internal 64-byte latch and timer eliminate host timing overhead-enables burst writes without CPU polling between bytes. |
| DATA Polling & Toggle Bit | I/O7 complement and I/O6 toggling provide real-time, hardware-verified write completion signals-replaces fixed-delay waits with deterministic status checks. |
| Hardware Write Protection | VCC sense, 5 ms power-on delay, and noise filtering prevent spurious writes during brown-out or EMI events-critical for system reliability in noisy factory environments. |
| Software Data Protection | User-configurable 3-byte command sequence (AAh/55h/A0h) enables/disables write lock-prevents accidental overwrites during firmware updates or debug sessions. |
| Device Identification Area | 64-byte auxiliary EEPROM accessible via 12 V on A9 and addresses 7FC0h–7FFFh-supports unique serialization, calibration data, or revision tracking without consuming main array space. |
Applications
| Industrial PLC Configuration Storage | Medical Device Calibration Memory |
|---|---|
Use Scenario: Storing user-modifiable I/O mapping, PID tuning parameters, and alarm thresholds in programmable logic controllers deployed in factory automation lines. IC Role / Device Role / Timing Role: Nonvolatile configuration register accessed via parallel bus during startup and runtime; 90 ns read speed ensures minimal boot delay. Use Value: Enables field reconfiguration without firmware reflashing; 10-year data retention guarantees parameter integrity across maintenance cycles. | Use Scenario: Holding sensor calibration coefficients, patient history flags, and safety-critical operational limits in portable diagnostic equipment. IC Role / Device Role / Timing Role: Secure, tamper-resistant parameter store with software/hardware write lock; accessed during power-up and before measurement cycles. Use Value: Prevents unauthorized or accidental modification of calibration data; 10⁴-cycle endurance supports repeated recalibration over device lifetime. |
| Automotive Body Control Module NVM | Test Equipment Firmware Patch Storage |
Use Scenario: Saving seat/mirror position presets, lighting profiles, and error logs in automotive BCMs operating across −40°C to +85°C ambient. IC Role / Device Role / Timing Role: Industrial-grade EEPROM interfaced directly to 8-bit microcontroller bus; withstands thermal cycling and vibration. Use Value: Eliminates need for external voltage supervisors or write-protect jumpers; green (Pb/Halide-free) packaging meets automotive RoHS requirements. | Use Scenario: Hosting field-upgradable test algorithms, fixture-specific compensation tables, and pass/fail criteria in automated bench testers. IC Role / Device Role / Timing Role: High-reliability patch memory supporting in-system page writes via JTAG or UART bootloader. Use Value: Reduces downtime by enabling firmware patches without hardware replacement; 3 ms fast-write option accelerates update throughput. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar parallel EEPROM applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AT28C256-90PI | Same pinout and timing, but lacks software data protection and 12 V device ID area; endurance rated at 10⁴ cycles only. | Suitable for cost-sensitive designs where write protection is handled externally or unnecessary. | Select AT28C256-90PI only if software lock and auxiliary EEPROM are unused; verify VCC sense behavior matches system power ramp profile. |
| MX28F256J3F-90PC | 32-pin PLCC package; 90 ns access; 10⁵ endurance; includes hardware write protect pin (WP#) instead of software-only lock. | Requires PCB layout change; better suited for new designs needing dedicated hardware write inhibit and higher endurance. | Choose MX28F256J3F-90PC for new industrial boards prioritizing hardware-level write security and extended lifecycle; not drop-in compatible. |
Compared with AT28HC256-90PI, AT28C256-90PI reduces feature set and reliability margin but lowers BOM cost, while MX28F256J3F-90PC trades package compatibility for enhanced hardware protection and endurance-making AT28HC256-90PI optimal for legacy 28-pin PDIP upgrades requiring full feature retention.
Availability
AT28HC256-90PI is available at Aetrix Electronics and suitable for industrial control systems, medical instrumentation, automotive body electronics, and test equipment requiring stable component supply across extended temperature ranges and long product lifecycles.
Supply support for AT28HC256-90PI 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 engineered for robust, field-upgradable nonvolatile storage in industrial and automotive systems where reliability, long data retention, and compatibility with legacy 5 V parallel buses are essential.
FAQ
What is the maximum page write size supported by the AT28HC256-90PI?
The AT28HC256-90PI supports up to 64 bytes per page write operation. This is enabled by its internal 64-byte page register, which latches address and data during the first byte write and allows up to 63 additional bytes to be loaded within 150 µs of each prior byte. All bytes must reside on the same page, defined by identical A6–A14 values. The AT28HC256-90PI does not support larger block writes or sector erases.
How does the AT28HC256-90PI indicate write completion without using a fixed delay?
The AT28HC256-90PI provides two hardware methods: DATA Polling (I/O7 returns complement of last written data until completion, then true data) and Toggle Bit (I/O6 toggles between 0 and 1 during write, then stabilizes). Both can be polled at any time during the write cycle. These mechanisms eliminate reliance on worst-case timing delays and improve system responsiveness in the AT28HC256-90PI.
Does the AT28HC256-90PI require a 12 V supply for normal operation?
No, the AT28HC256-90PI operates solely from a 5 V ±10% supply. The 12 V requirement applies only to accessing the optional 64-byte device identification EEPROM, which is activated by raising A9 to 12.0 V ± 0.5 V. All standard read, write, and page operations use only the 5 V rail-no external high-voltage generator is needed for core AT28HC256-90PI functionality.
What is the purpose of the software data protection (SDP) feature in the AT28HC256-90PI?
The SDP feature in the AT28HC256-90PI prevents inadvertent writes via a user-enabled lock requiring a specific three-byte command sequence (AAh → 55h → A0h). Once enabled, all subsequent writes must be preceded by this sequence-even protected writes. SDP persists across power cycles and is disabled only by another verified sequence (AAh → 55h → 80h → AAh → 20h). This adds a layer of firmware-controlled security absent in basic AT28HC256-90PI variants.
Can the AT28HC256-90PI be used as a direct replacement for the AT28C256-90PI on an existing PCB?
Yes, the AT28HC256-90PI is pin- and function-compatible with the AT28C256-90PI in the same 28-pin PDIP package and operates with identical timing and voltage specifications. However, the AT28HC256-90PI adds software data protection and device ID EEPROM-features that remain inert unless explicitly invoked. No PCB changes are required, but firmware may need updates to leverage new AT28HC256-90PI capabilities or avoid unintended SDP activation.
AT28HC256-90PI 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:
- 90 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
AT28HC256-90PI FAQ
1.How can I place an order for AT28HC256-90PI through Aetrix?
Please submit a Request for Quotation (RFQ) for AT28HC256-90PI 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 AT28HC256-90PI reliable?
The price and inventory of AT28HC256-90PI are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AT28HC256-90PI is usually 5 days.
3.What payment methods are accepted for AT28HC256-90PI?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AT28HC256-90PI transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AT28HC256-90PI?
AT28HC256-90PI orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AT28HC256-90PI 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 AT28HC256-90PI?
For technical support, including AT28HC256-90PI datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AT28HC256-90PI requirements.
6.How does Aetrix verify that AT28HC256-90PI is sourced from the original manufacturer or authorized distributors?
All AT28HC256-90PI 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 AT28HC256-90PI meets industry standards.
7.What is the process for return or replacement of AT28HC256-90PI?
All AT28HC256-90PI units undergo pre-shipment inspection (PSI). If there is an issue with AT28HC256-90PI, 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 AT28HC256-90PI part is unused and in its original packaging.
Return procedure for AT28HC256-90PI:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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