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Microchip Technology AT29C256-90PI
- Part No.:
- AT29C256-90PI
- Manufacturer:
- Microchip Technology
- Category:
- Memory
- Package:
- 28-DIP (0.600", 15.24mm)
- Datasheet:
-
AT29C256-90PI.pdf
- Description:
- IC FLASH 256KBIT PARALLEL 28DIP
- Quantity:
- Payment:
- Shipping:
Inventory:1,842
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Product details
Overview
AT29C256-90PI from Atmel is a 256 Kbit (32K × 8) 5V-only Flash memory IC used for nonvolatile program/data storage in embedded microcontroller systems, industrial controllers, and legacy BIOS firmware. It delivers 90 ns read access time, supports page programming of 64-byte blocks, and operates across -40°C to +85°C industrial temperature range with CMOS/TTL-compatible I/O.
For engineers reviewing the AT29C256-90PI datasheet, AT29C256-90PI pinout, AT29C256-90PI application, or AT29C256-90PI equivalent, key selection criteria include its 5V-only reprogramming architecture, hardware/software data protection, DATA polling and toggle-bit program status detection, and compatibility with PLCC, PDIP, and TSOP packages.
Technical Context
The AT29C256-90PI implements a page-based Flash architecture where 64-byte pages are erased and programmed in a single internal cycle using on-chip timing control. Its dual-line chip enable (CE) and output enable (OE) logic enables flexible bus interfacing without contention during mixed read/write operations.
It integrates both hardware-level VCC sensing (program inhibit below 3.8 V), noise filtering (<15 ns pulse rejection), and software-controlled data protection via three-byte command sequences at fixed addresses (5555H/2AAAH). The device uses standard parallel address/data bus signaling with no external high-voltage programming supply required.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory Density | 256 Kbit (32,768 × 8 bits) - sufficient for boot code, configuration tables, or firmware patches in resource-constrained systems |
| Read Access Time | 90 ns - ensures compatibility with 10 MHz system buses without wait states |
| Page Program Time | 10 ms per 64-byte page - enables rapid field updates without full-chip erase overhead |
| VCC Supply Range | 5 V ± 10% - supports operation across wide input tolerance without external regulation |
| Endurance | >10,000 write/erase cycles per sector - suitable for applications requiring infrequent but reliable firmware updates |
| Standby Current | 300 µA (CMOS) - minimizes power draw in sleep or idle modes of battery-backed systems |
| Operating Temperature | -40°C to +85°C - validated for industrial environments including factory automation and motor drives |
Pinout & Package
AT29C256-90PI is available in 28-pin PDIP (28P6) package with 0.600" width. Pin 1 is index corner; pins 1–14 and 15–28 form two opposing rows. Pins 1 and 17 are NC (no connect) in PLCC variant but not present in PDIP; this PDIP variant has no NC pins.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| A0–A14 | Address Inputs | 15-bit address bus supporting full 32K-word addressing; A0–A5 select byte within 64-byte page during programming |
| I/O0–I/O7 | Bidirectional Data Bus | 8-bit parallel interface for read/write; latched during byte load; supports DATA polling on I/O7 and toggle-bit detection on I/O6 |
| CE | Chip Enable | Active-low global enable; must be low for read, program, or erase; high-Z outputs when high |
| OE | Output Enable | Active-low output gate; controls data assertion on I/O lines during read; must be high during programming |
| WE | Write Enable | Active-low control for byte loading and program initiation; timing-critical for 150 µs inter-byte window in page load |
| VCC | Power Supply | +5 V ± 10% main supply; powers core logic and I/O drivers; enables internal voltage sensing for program safety |
| GND | Ground Reference | Signal and power return path; referenced for all input thresholds and output levels |
Key Features
| Feature | Design Value |
|---|---|
| 5V-only reprogramming | Eliminates need for +12 V programming supply - simplifies PCB layout and reduces BOM count |
| Internal page latching | 64-byte data and address held internally during program cycle - frees external bus for concurrent operations |
| Hardware data protection | VCC sense, 5 ms power-on delay, and noise filtering prevent accidental writes during brown-out or EMI events |
| Software data protection | Three-byte unlock sequence (5555H/2AAAH/A0H) required before each program - prevents unintended firmware corruption |
| DATA polling & toggle-bit | Real-time program status feedback via I/O7 complement or I/O6 toggling - avoids fixed-delay polling loops |
Applications
| Industrial PLC Firmware Storage | Legacy PC BIOS Memory |
|---|---|
Use Scenario: Storing ladder logic programs and I/O configuration data in programmable logic controllers deployed in factory environments. IC Role / Device Role / Timing Role: Nonvolatile storage for executable firmware and runtime parameters; accessed via parallel bus during boot and runtime updates. Use Value: 90 ns read speed enables deterministic scan-cycle timing; industrial temp rating (-40°C to +85°C) ensures reliability in uncontrolled cabinet environments. |
Use Scenario: Holding BIOS initialization code and hardware configuration tables in desktop motherboards prior to transition to SPI Flash. IC Role / Device Role / Timing Role: Boot ROM providing early-stage x86 CPU instruction fetch and hardware enumeration; mapped to upper memory space (e.g., F0000H–FFFFFH). Use Value: Pin-compatible replacement for older EPROMs; 5V-only operation eliminates UV-eraser dependency and high-voltage programming circuitry. |
| Embedded Controller Code Storage | Telecom Line Card Configuration |
Use Scenario: Hosting application firmware and calibration constants in HVAC controllers, medical infusion pumps, and test equipment. IC Role / Device Role / Timing Role: Executable code storage with in-system update capability; accessed by microcontroller's external memory interface. Use Value: Page-programming allows partial firmware patching without erasing entire image; >10,000 endurance supports field service life over 10+ years. |
Use Scenario: Storing line protocol settings, DSP coefficients, and vendor-specific parameters in DSLAM and PBX line cards. IC Role / Device Role / Timing Role: Configuration memory read during card power-up and updated during remote provisioning or diagnostics. Use Value: Hardware/software protection prevents misconfiguration during hot-swap or network-induced transients; 300 µA standby current minimizes backplane loading. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar Flash memory applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AT29C256-90JI | Same die and timing specs; packaged in 32-lead PLCC (32J) instead of 28-pin PDIP | Requires different PCB footprint and socket; better thermal dissipation and higher pin-count flexibility | Select for surface-mount designs or when additional NC pins aid routing |
| MX29LV256EITI-90G | 3.3 V core with 5 V tolerant I/O; 90 ns access; 256 Mbit density; supports CFI command set | Not 5V-only; requires level-shifting or dual-supply design; larger capacity may exceed legacy address decoding | Choose only if migrating to lower-power 3.3 V systems with updated controller support |
Compared with AT29C256-90PI, AT29C256-90JI offers identical functionality in a surface-mount PLCC package ideal for automated assembly, while MX29LV256EITI-90G provides modern 3.3 V operation and CFI compliance but demands hardware and firmware redesign - making AT29C256-90PI the optimal drop-in replacement for existing 5V parallel Flash designs.
Availability
AT29C256-90PI is available at Aetrix Electronics and suitable for industrial PLC firmware storage, legacy PC BIOS memory, and embedded controller code storage requiring stable component supply across extended product lifecycles.
Supply support for AT29C256-90PI 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, Flash memory, and secure authentication devices.
The AT29C256 product line was designed for cost-sensitive, 5V-based embedded systems needing field-upgradable nonvolatile storage without high-voltage programming infrastructure.
FAQ
What is the maximum operating frequency supported by AT29C256-90PI?
The AT29C256-90PI does not operate at a clock frequency like a synchronous device. Its 90 ns read access time corresponds to a maximum effective bus toggle rate of approximately 11 MHz under ideal conditions. System timing must comply with AC specifications including tCE (90 ns CE-to-output), tOE (40 ns OE-to-output), and tDF (25 ns float time), with actual throughput limited by microcontroller interface capabilities and board-level signal integrity.
Does AT29C256-90PI require external high-voltage programming circuitry?
No, AT29C256-90PI does not require external high-voltage programming circuitry. It is a 5V-only Flash memory: all programming and erasure operations use standard 5 V ± 10% VCC with no auxiliary voltages. Programming is initiated via specific WE/CE/OE control sequences and address/data patterns - eliminating the need for +12 V generators or UV erasers required by older EPROMs.
How is program completion detected on AT29C256-90PI?
Program completion on AT29C256-90PI is detected using either DATA polling on I/O7 or the toggle-bit method on I/O6. During programming, reading the last loaded byte returns the complement of the data on I/O7; when complete, true data appears. Alternatively, I/O6 toggles between 0 and 1 during active programming and stabilizes once complete - both methods allow real-time status monitoring without fixed delays.
What package type is used for AT29C256-90PI?
AT29C256-90PI uses the 28-lead, 0.600" wide plastic dual inline package (PDIP), designated as 28P6 in Atmel's ordering nomenclature. This through-hole package features standard 0.1" pin spacing, is RoHS-compliant, and is compatible with legacy sockets and wave-solder processes used in industrial control and telecom hardware.
Is software data protection enabled by default on AT29C256-90PI?
No, software data protection is disabled by default on AT29C256-90PI when shipped from the factory. It must be explicitly enabled using the three-byte unlock sequence (write AAH to 5555H, 55H to 2AAAH, then A0H to 5555H). Once enabled, all subsequent programming requires repeating this sequence - providing controlled write access while preventing accidental firmware corruption during power transitions or noise events.
AT29C256-90PI 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:
- FLASH
- Technology:
- FLASH
- 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
AT29C256-90PI FAQ
1.How can I place an order for AT29C256-90PI through Aetrix?
Please submit a Request for Quotation (RFQ) for AT29C256-90PI 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 AT29C256-90PI reliable?
The price and inventory of AT29C256-90PI are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AT29C256-90PI is usually 5 days.
3.What payment methods are accepted for AT29C256-90PI?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AT29C256-90PI transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AT29C256-90PI?
AT29C256-90PI orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AT29C256-90PI 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 AT29C256-90PI?
For technical support, including AT29C256-90PI datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AT29C256-90PI requirements.
6.How does Aetrix verify that AT29C256-90PI is sourced from the original manufacturer or authorized distributors?
All AT29C256-90PI 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 AT29C256-90PI meets industry standards.
7.What is the process for return or replacement of AT29C256-90PI?
All AT29C256-90PI units undergo pre-shipment inspection (PSI). If there is an issue with AT29C256-90PI, 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 AT29C256-90PI part is unused and in its original packaging.
Return procedure for AT29C256-90PI:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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