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Microchip Technology AT28HC256-70JI
- Part No.:
- AT28HC256-70JI
- Manufacturer:
- Microchip Technology
- Category:
- Memory
- Package:
- 32-LCC (J-Lead)
- Datasheet:
-
AT28HC256-70JI.pdf
- Description:
- IC EEPROM 256KBIT PAR 32PLCC
- Quantity:
- Payment:
- Shipping:
Inventory:4,085
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Product details
Overview
AT28HC256-70JI from Atmel is a 256 Kbit (32K × 8) parallel EEPROM with 70 ns read access time, JEDEC-standard byte-wide pinout, and industrial temperature range (–40°C to +85°C). It supports automatic 1–64-byte page writes with internal latching and timer, operates on single 5V ±10% supply, and delivers 80 mA active current and ≤60 mA standby current. It is used in embedded control firmware storage, industrial PLC configuration memory, and legacy system BIOS backup.
For engineers reviewing the AT28HC256-70JI datasheet, AT28HC256-70JI pinout, AT28HC256-70JI application, or AT28HC256-70JI equivalent, key selection considerations include its 70 ns read timing, page-write endurance (10⁴ cycles), hardware/software write protection, DATA polling and toggle-bit write completion detection, and compatibility with TTL/CMOS bus interfaces in space-constrained industrial designs.
Technical Context
The AT28HC256-70JI implements a CMOS-based parallel EEPROM architecture with integrated address/data latches for 64-byte page buffering and an internal control timer that autonomously executes write cycles after data loading. Its dual-line chip enable (CE) and output enable (OE) logic enables flexible bus contention management in multi-device systems.
Write operation relies on either WE- or CE-controlled strobes with strict timing windows (tBLC ≤150 µs between bytes in page mode), while end-of-write detection is supported via I/O7 DATA polling or I/O6 toggle-bit monitoring - both usable at any point during the write cycle without halting host operations.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory Size | 256 Kbit (32,768 × 8), organized as byte-addressable parallel array |
| Read Access Time | 70 ns - enables direct replacement of SRAM in legacy 5 MHz bus systems |
| Page Write Cycle Time | Max 10 ms - supports burst programming of up to 64 bytes per internal cycle |
| Endurance | 10,000 write/erase cycles - validated for firmware update logging in industrial controllers |
| Data Retention | 10 years at 85°C - ensures long-term reliability in unattended equipment |
| Supply Voltage | 5 V ±10% - compatible with standard TTL/CMOS logic rails without regulation |
| Operating Temperature | –40°C to +85°C - qualified for industrial-grade PCB deployment |
| Interface Standard | JEDEC-approved byte-wide parallel - drop-in compatible with existing 28-pin socket layouts |
Pinout & Package
AT28HC256-70JI is supplied in a 28-lead plastic dual-inline package (PDIP), 0.600" wide (28P6), with JEDEC MS-011 AB-compliant footprint and through-hole mounting.
| 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; supports true read/write and high-impedance tri-state during deselect |
| CE | Chip Enable | Active-low device select; when high, forces standby mode and disables outputs regardless of OE/WE state |
| OE | Output Enable | Active-low output gate; allows shared bus operation by disabling outputs while CE remains low |
| WE | Write Enable | Active-low write strobe; initiates byte or page write on falling edge, latching address and data |
| VCC, GND | Power Supply | Single 5V supply with decoupling required; ground reference for all I/O and internal logic |
| NC | No Connect | Unbonded pins (e.g., PDIP pins 12, 26); must remain floating per datasheet |
Key Features
| Feature | Design Value |
|---|---|
| Automatic Page Write | Reduces firmware update latency by enabling 64-byte bursts with single initiation, freeing address/data bus mid-cycle |
| DATA Polling & Toggle Bit | Enables non-blocking write status checking via I/O7 complement or I/O6 toggling - no dedicated status register needed |
| Hardware Write Protection | VCC sense (<3.8 V inhibits write), 5 ms power-on delay, and noise filtering (<15 ns pulses ignored) prevent spurious writes during brown-out |
| Software Data Protection (SDP) | User-configurable lock via 3-byte command sequence (5555h/2AAAh/5555h + A0h); persists across power cycles and requires re-entry for each protected write |
| Extended Identification Area | 64-byte EEPROM segment (7FC0h–7FFFh) accessible at 12 V on A9 for device serialization or calibration data storage |
Applications
| Industrial PLC Configuration Storage | Legacy System BIOS Backup |
|---|---|
Use Scenario: Storing runtime-modifiable ladder logic parameters and I/O mapping tables in programmable logic controllers deployed in factory automation lines. IC Role / Device Role / Timing Role: Nonvolatile configuration memory accessed via parallel bus during boot and runtime; 70 ns read speed ensures real-time parameter fetch without CPU stall. Use Value: Eliminates need for battery-backed SRAM; 10⁴ endurance supports daily firmware updates over 27 years; industrial temp rating ensures operation inside sealed enclosures. | Use Scenario: Preserving BIOS settings and boot loader code in aging x86-based industrial PCs where flash memory is unavailable or unsupported. IC Role / Device Role / Timing Role: Parallel EEPROM replacing obsolete EPROMs; JEDEC pinout allows direct socket replacement without PCB redesign. Use Value: 5V-only operation avoids level-shifting; page write reduces POST time vs. byte-by-byte programming; SDP prevents accidental corruption during field service. |
| Embedded Controller Firmware Log | Medical Device Calibration Memory |
Use Scenario: Recording fault codes, sensor calibration deltas, and operational hours in standalone medical infusion pumps requiring traceable event history. IC Role / Device Role / Timing Role: High-reliability data logger using page writes to minimize write wear; DATA polling confirms write completion before next log entry. Use Value: 10-year data retention meets FDA audit requirements; hardware VCC-sense protection prevents log corruption during AC power interruption. | Use Scenario: Storing factory-calibrated ADC offset/gain coefficients and user-adjusted therapy parameters in portable diagnostic ultrasound units. IC Role / Device Role / Timing Role: Secure configuration store with software data protection enabled; 12 V A9 access enables one-time calibration write during manufacturing. Use Value: SDP prevents field tampering; extended ID area stores unique serial numbers and calibration timestamps; industrial temp range covers clinical environment fluctuations. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar parallel EEPROM applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AT28C256-70JI | Same pinout and timing, but lacks software data protection and extended ID area; endurance rated at 10⁴ cycles same as AT28HC256 | No SDP or 12 V calibration area - unsuitable where firmware integrity or device serialization is required | Select only if cost sensitivity outweighs security and traceability needs |
| MX28F256J3F-70I | 32-pin PLCC, 70 ns access, 10⁵ endurance, 3 ms fast write option; requires different footprint and layout | Higher endurance and faster write, but incompatible pinout and package - demands PCB revision | Choose for new designs needing extended lifecycle; not a drop-in replacement |
Compared with AT28HC256-70JI, AT28C256-70JI offers identical timing and industrial temperature support but omits critical security features, while MX28F256J3F-70I provides superior endurance and speed at the cost of mechanical and electrical incompatibility - making AT28HC256-70JI the optimal balance of legacy compatibility, protection, and qualification for retrofit and long-lifecycle industrial use.
Availability
AT28HC256-70JI is available at Aetrix Electronics and suitable for industrial PLC configuration storage, legacy system BIOS backup, and embedded controller firmware logging requiring stable component supply across extended production lifecycles.
Supply support for AT28HC256-70JI 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 ICs.
The AT28HC256 belongs to Atmel's parallel EEPROM product line, designed specifically for industrial and automotive applications demanding high reliability, robust write protection, and seamless integration into legacy 5 V bus architectures.
FAQ
What is the maximum page write size supported by the AT28HC256-70JI?
The AT28HC256-70JI supports page writes of 1 to 64 bytes per internal programming cycle. All bytes written within a single page operation must reside on the same 64-byte page boundary defined by address bits A6–A14. The device internally latches the address and data, then executes the write autonomously using its internal control timer - no external timing control is required beyond meeting the 150 µs byte-load cycle (tBLC) limit.
Does the AT28HC256-70JI require a 12 V supply for normal operation?
No, the AT28HC256-70JI operates exclusively from a single 5 V ±10% supply under all standard read, write, and standby conditions. A 12 V ±0.5 V voltage applied to pin A9 is required only for accessing the optional 64-byte extended identification area (7FC0h–7FFFh) during factory calibration - this is a one-time or infrequent operation and does not affect routine functionality of the AT28HC256-70JI.
How does software data protection (SDP) function on the AT28HC256-70JI?
Software data protection on the AT28HC256-70JI is enabled by writing a specific three-byte sequence (AAh to 5555h, 55h to 2AAAh, A0h to 5555h) to activate lock mode. Once set, all subsequent writes to the AT28HC256-70JI require repeating this sequence before data - ensuring accidental overwrites are blocked. SDP persists across power cycles and is disabled only by issuing a separate five-byte unlock sequence. The AT28HC256-70JI ships with SDP disabled.
Can the AT28HC256-70JI be used as a direct replacement for older EPROMs like the 27C256?
No - the AT28HC256-70JI is not a functional or pinout-compatible replacement for UV-erasable EPROMs such as the 27C256. While both are 28-pin, 256 Kbit parallel memories, the AT28HC256-70JI uses different control signal timing (CE/OE/WE vs. CE/OE/G), lacks UV window, and requires no programming voltage. It replaces EPROMs only in systems redesigned to support EEPROM write cycles and DATA polling - not as a socket-level drop-in.
What packaging options are available for the AT28HC256-70JI?
The AT28HC256-70JI is packaged in a 28-lead plastic dual-inline package (PDIP), 0.600" wide (ordering code suffix "PI"), compliant with JEDEC MS-011 AB. This through-hole package is distinct from other variants like the TSOP (suffix "TI") or PLCC (suffix "JI") - the "JI" in AT28HC256-70JI refers to industrial temperature grade, not package type; the actual package for this part number is PDIP. Datasheet section 27.1 confirms AT28HC256-70JI maps to 28P6.
AT28HC256-70JI Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Microchip Technology
- Series:
- -
- Package/Case:
- 32-LCC (J-Lead)
- 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:
- 70 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 (13.97x11.43)
AT28HC256-70JI FAQ
1.How can I place an order for AT28HC256-70JI through Aetrix?
Please submit a Request for Quotation (RFQ) for AT28HC256-70JI 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 AT28HC256-70JI reliable?
The price and inventory of AT28HC256-70JI are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AT28HC256-70JI is usually 5 days.
3.What payment methods are accepted for AT28HC256-70JI?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AT28HC256-70JI transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AT28HC256-70JI?
AT28HC256-70JI orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AT28HC256-70JI 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 AT28HC256-70JI?
For technical support, including AT28HC256-70JI datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AT28HC256-70JI requirements.
6.How does Aetrix verify that AT28HC256-70JI is sourced from the original manufacturer or authorized distributors?
All AT28HC256-70JI 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 AT28HC256-70JI meets industry standards.
7.What is the process for return or replacement of AT28HC256-70JI?
All AT28HC256-70JI units undergo pre-shipment inspection (PSI). If there is an issue with AT28HC256-70JI, 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 AT28HC256-70JI part is unused and in its original packaging.
Return procedure for AT28HC256-70JI:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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