My Inquiry
My Account
Microchip Technology AT28HC256-12JI
- Part No.:
- AT28HC256-12JI
- Manufacturer:
- Microchip Technology
- Category:
- Memory
- Package:
- 32-LCC (J-Lead)
- Datasheet:
-
AT28HC256-12JI.pdf
- Description:
- IC EEPROM 256KBIT PAR 32PLCC
- Quantity:
- Payment:
- Shipping:
Inventory:1,285
Please send an inquiry. Send us your inquiry, and we will respond immediately.
Product details
Overview
AT28HC256-12JI from Microchip Technology (formerly Atmel) is a 256 Kbit (32K × 8) parallel EEPROM IC used for nonvolatile program/data storage in embedded control and instrumentation systems. It delivers 120 ns read access time, supports 1–64-byte page writes with ≤10 ms internal write cycle, operates on single 5V ±10% supply, and is rated for industrial temperature range (−40°C to +85°C) in 28-pin SOIC package.
For engineers reviewing the AT28HC256-12JI datasheet, AT28HC256-12JI pinout, AT28HC256-12JI application, or AT28HC256-12JI equivalent, key selection considerations include JEDEC-standard byte-wide parallel interface timing, hardware/software data protection mechanisms, DATA polling and toggle-bit write completion detection, and compatibility with legacy SRAM-based memory bus designs.
Technical Context
The AT28HC256-12JI implements a CMOS-based parallel EEPROM architecture with internal address/data latching for page write operations. Its 64-byte page register enables burst programming without external address management, while VCC sense and noise-filtered WE/CE inputs provide robust hardware write inhibition during power transitions.
It features dual write detection methods-DATA polling on I/O7 and toggle-bit monitoring on I/O6-and includes optional software data protection (SDP) activated via a 3-byte command sequence. The device also integrates 64 bytes of dedicated identification EEPROM accessible at 7FC0H–7FFFH using A9 = 12V.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory Density | 256 Kbit (32,768 × 8), directly replaceable in SRAM-style 8-bit data bus systems |
| Read Access Time | 120 ns maximum - defines minimum clock period for synchronous read cycles |
| Page Write Cycle Time | ≤10 ms - determines worst-case firmware delay before next memory access |
| Supply Voltage | 5V ±10% - compatible with standard TTL/CMOS logic rails without regulation |
| Operating Temperature | −40°C to +85°C - qualified for industrial-grade embedded controller environments |
| Endurance | 10,000 write/erase cycles - supports field-updatable firmware or configuration storage |
| Data Retention | 10 years at +85°C - ensures long-term reliability in unattended equipment |
Pinout & Package
AT28HC256-12JI is supplied in a 28-lead, 0.300" wide plastic gull-wing small outline (SOIC) package per JEDEC MS-013, with 300 mil body width and 1.27 mm lead pitch.
| 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 page writes |
| I/O0–I/O7 | Bi-directional Data Bus | 8-bit parallel interface compatible with microcontroller data buses; supports true read/write without direction control |
| 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 control; used with CE to prevent bus contention during multi-device sharing |
| WE | Write Enable | Active-low write strobe; falling edge latches address and data; initiates byte or page write |
| VCC | Power Supply | +5V ±10% supply input; internal VCC sense disables writes below ~3.8V |
| GND | Ground Reference | Signal and power return; decoupling capacitor required within 1 cm of VCC pin |
Key Features
| Feature | Design Value |
|---|---|
| JEDEC Byte-wide Pinout | Direct drop-in replacement for 27C256/62256 SRAMs without PCB redesign |
| 64-byte Page Write | Reduces firmware overhead by enabling up to 64 bytes per write command instead of 64 individual byte writes |
| DATA Polling & Toggle Bit | Enables real-time write status monitoring without timer delays or external hardware |
| Hardware Write Protection | VCC sense, 5 ms power-on delay, and noise filtering eliminate spurious writes during brown-out or EMI events |
| Software Data Protection (SDP) | User-configurable lock/unlock via 3-byte command sequence; persists across power cycles |
Applications
| Industrial PLC Configuration Storage | Medical Device Calibration Data |
|---|---|
Use Scenario: Storing user-modifiable I/O mapping and alarm thresholds in programmable logic controllers. IC Role / Device Role / Timing Role: Nonvolatile configuration memory accessed via 8-bit parallel bus during boot and runtime reconfiguration. Use Value: 10,000-cycle endurance and 10-year retention ensure reliable operation over 15+ year equipment lifecycles without battery backup. | Use Scenario: Holding factory-calibrated sensor offsets and gain coefficients in portable diagnostic instruments. IC Role / Device Role / Timing Role: Secure, write-protected data storage accessed only during calibration mode using SDP unlock sequence. Use Value: Hardware VCC-sense and software protection prevent accidental corruption during clinical use or battery swaps. |
| Avionics System Bootloader Code | Test Equipment Firmware Patch Storage |
Use Scenario: Hosting immutable bootloader code executed on power-up in airborne flight control modules. IC Role / Device Role / Timing Role: Read-only execution memory with 120 ns access time meeting deterministic timing budgets for safety-critical startup sequences. Use Value: Industrial temperature rating and 5V-only operation simplify power design and eliminate level-shifting requirements. | Use Scenario: Storing field-deployable firmware patches loaded during maintenance windows on automated test systems. IC Role / Device Role / Timing Role: Field-upgradable program memory supporting 64-byte page writes to minimize downtime during patch application. Use Value: ≤10 ms page write time enables sub-second patch updates without halting production test sequences. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar parallel EEPROM applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AT28C256-12JI | Same pinout and timing, but lacks software data protection and 64-byte page register; 10 ms write cycle only | Suitable where simplified firmware and lower cost outweigh SDP and page-write benefits | Select when write protection is handled externally and page write is unnecessary |
| MN5Q2568B-12L | 120 ns access, 32K × 8, but requires 12V VPP for programming; no built-in page latch or SDP | Used in legacy systems requiring high-voltage programming; incompatible with 5V-only designs | Choose only if existing board provides 12V VPP and firmware supports high-voltage protocol |
Compared with AT28C256-12JI, the AT28HC256-12JI adds page write and SDP at identical speed and package, while MN5Q2568B-12L demands external high-voltage support and offers no firmware-level write safeguards.
Availability
AT28HC256-12JI is available at Aetrix Electronics and suitable for industrial control, medical instrumentation, avionics subsystems, and automated test equipment requiring stable component supply across extended product lifecycles.
Supply support for AT28HC256-12JI 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 legacy Atmel parallel EEPROM products including the AT28HC256 family.
The AT28HC256 product line was designed for direct replacement of EPROM and SRAM in legacy 8-bit microcontroller systems, emphasizing pin compatibility, JEDEC-standard timing, and robust data integrity under industrial operating conditions.
FAQ
What is the maximum page write size supported by the AT28HC256-12JI?
The AT28HC256-12JI supports page write operations of 1 to 64 bytes per internal programming cycle. All bytes must reside on the same page, defined by address bits A6–A14. The device internally latches the address and data, freeing the bus for other operations after initiation. This capability is confirmed in Section 4.3 of the official datasheet and applies specifically to the AT28HC256-12JI variant.
Does the AT28HC256-12JI require a 12V programming voltage?
No, the AT28HC256-12JI operates with a single 5V ±10% supply for both read and write functions. A 12V signal on A9 is required only for accessing the optional 64-byte device identification EEPROM (7FC0H–7FFFH), not for main array programming. Standard byte and page writes use only 5V, making the AT28HC256-12JI compatible with 5V-only system designs.
How does hardware write protection work on the AT28HC256-12JI?
The AT28HC256-12JI implements four hardware write protection mechanisms: (1) VCC sense circuitry inhibits writes below ~3.8V, (2) automatic 5 ms power-on delay before write enable, (3) write inhibition when OE is low or CE is high or WE is high, and (4) 15 ns noise filter on WE/CE inputs. These features are active by default and require no firmware configuration, ensuring robustness against power glitches and EMI - a core behavior of the AT28HC256-12JI.
Can the AT28HC256-12JI be used as a direct replacement for a 62256 SRAM?
Yes, the AT28HC256-12JI uses JEDEC-approved byte-wide pinout and operates like an SRAM for reads and writes, allowing drop-in replacement in many 62256-based designs. However, write cycles require explicit timing management (e.g., DATA polling), and standby current is higher than typical SRAM. The AT28HC256-12JI retains data without power, eliminating battery backup needs - a functional advantage over 62256.
What is the purpose of the extra 64 bytes of EEPROM in the AT28HC256-12JI?
The AT28HC256-12JI includes 64 bytes of dedicated identification EEPROM mapped to addresses 7FC0H–7FFFH. Access requires raising A9 to 12V ±0.5V; otherwise, those locations read as FFH. This area is intended for storing unique device identifiers, calibration data, or manufacturing traceability codes - separate from the main 32K × 8 array. This feature is documented in Section 4.7 and applies to the AT28HC256-12JI.
AT28HC256-12JI 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:
- 120 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)
AT28HC256-12JI FAQ
1.How can I place an order for AT28HC256-12JI through Aetrix?
Please submit a Request for Quotation (RFQ) for AT28HC256-12JI 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 AT28HC256-12JI reliable?
The price and inventory of AT28HC256-12JI are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AT28HC256-12JI is usually 5 days.
3.What payment methods are accepted for AT28HC256-12JI?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AT28HC256-12JI transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AT28HC256-12JI?
AT28HC256-12JI orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AT28HC256-12JI 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 AT28HC256-12JI?
For technical support, including AT28HC256-12JI datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AT28HC256-12JI requirements.
6.How does Aetrix verify that AT28HC256-12JI is sourced from the original manufacturer or authorized distributors?
All AT28HC256-12JI 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 AT28HC256-12JI meets industry standards.
7.What is the process for return or replacement of AT28HC256-12JI?
All AT28HC256-12JI units undergo pre-shipment inspection (PSI). If there is an issue with AT28HC256-12JI, 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 AT28HC256-12JI part is unused and in its original packaging.
Return procedure for AT28HC256-12JI:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
AT28HC256-12JI Tags
-
M24C02-WMN6TP
STMicroelectronics
-
AT24C02C-XHM-T
Microchip Technology
-
AT21CS01-STUM10-T
Microchip Technology
-
AT24C02C-SSHM-T
Microchip Technology
-
24LC01BT-I/OT
Microchip Technology
-
M24C02-FMC6TG
STMicroelectronics
-
AT24CS02-SSHM-T
Microchip Technology
-
93LC46BT-I/OT
Microchip Technology
-
AT24C04C-SSHM-T
Microchip Technology
-
24LC01BT-I/SN
Microchip Technology
-
24AA02UIDT-I/OT
Microchip Technology
-
AT24C08C-STUM-T
Microchip Technology
Tech Hub
TTL and CMOS logic families differ in thresholds, loading, output drive, power and timing. This engineering guide compares 74HC and 74HCT, calculates noise margins and checks 3.3 V/5 V compatibility.
A practical engineering guide to 3.3V and 5V logic compatibility, input thresholds, resistor dividers, translator ICs, MOSFET level shifting, I2C pull-ups, timing limits and power-sequencing risks.
The 74HC595 uses push-pull logic outputs, while the TPIC6B595 uses 50 V open-drain DMOS sinks for higher-power loads. This guide compares timing, current limits, 3.3 V interfacing, load wiring, thermal…
The 74HC595 converts serial data into eight stable parallel outputs. This guide covers pin functions, shift and storage timing, OE and MR behavior, drive-current limits, cascading, voltage compatibilit…
A technical comparison of level-sensitive latches and edge-triggered flip-flops, covering timing windows, setup and hold limits, master–slave operation, time borrowing, race-through, HDL inference and…
A D latch stores one bit while Enable controls when data can pass. This reference covers gate-level operation, truth tables, transparency, setup and hold timing, LE versus OE, common ICs and practical …
An SR latch stores one bit through cross-coupled feedback. This engineering reference covers NOR and NAND implementations, truth tables, forbidden-state recovery, gated operation, switch debouncing, fa…
Latch circuits retain one bit through feedback. This technical reference covers SR and D latches, truth tables, transparency, timing limits, latch-versus-flip-flop behavior, applications and common log…
An engineering guide to LED driver operation, constant-current and constant-voltage outputs, linear and switching topologies, dimming, IC selection, calculations, replacement compatibility, and fault c…
Operational amplifier guide covering op amp basics, feedback, ideal vs real op amps, common configurations, buffer circuits, offset, bias current, gain-bandwidth, slew rate, rail-to-rail limits and sel…
