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Microchip Technology AT29C256-12PI
- Part No.:
- AT29C256-12PI
- Manufacturer:
- Microchip Technology
- Category:
- Memory
- Package:
- 28-DIP (0.600", 15.24mm)
- Datasheet:
-
AT29C256-12PI.pdf
- Description:
- IC FLASH 256KBIT PARALLEL 28DIP
- Quantity:
- Payment:
- Shipping:
Inventory:4,307
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Product details
Overview
AT29C256-12PI from Atmel is a 256 Kbit (32K × 8) 5V-only Flash memory IC used for nonvolatile program/data storage in embedded systems, supporting in-system reprogramming without high-voltage supplies. It delivers 120 ns read access time, 10 ms page (64-byte) program time, and operates across -40°C to +85°C industrial temperature range with CMOS/TTL-compatible I/O.
For engineers reviewing the AT29C256-12PI datasheet, AT29C256-12PI pinout, AT29C256-12PI application, or AT29C256-12PI equivalent, key selection criteria include its 5V-only operation, software/hardware data protection, DATA polling and toggle-bit programming status detection, and support for PLCC, PDIP, and TSOP packages - all critical for legacy industrial controller and firmware update designs.
Technical Context
The AT29C256-12PI implements a page-programmable Flash architecture where 64-byte pages are loaded via byte-load cycles before internal erase-and-program execution. Its control logic uses CE/OE/WE three-line protocol identical to SRAM for reads, while writes require specific address/data sequences and timing constraints including 150 µs inter-byte load window and tWC = 10 ms write cycle time.
Hardware protection includes VCC sense (<3.8 V inhibits programming), 5 ms power-on delay, noise filtering (<15 ns pulses ignored), and active-level inhibition (OE low, CE high, or WE high blocks writes). Software protection uses a 3-byte unlock sequence (AAh/55h/A0h) to enable or disable write operations, persisting across power cycles.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory Size | 256 Kbit (32,768 × 8 bits) - supports full firmware images or configuration tables in space-constrained industrial controllers. |
| Read Access Time | 120 ns - enables direct replacement of slower EPROMs or SRAM in legacy bus interfaces without timing redesign. |
| Page Program Time | 10 ms per 64-byte page - allows efficient field updates with minimal system downtime during firmware patches. |
| Endurance | >10,000 write/erase cycles - suitable for applications requiring infrequent but reliable field reprogramming over product lifetime. |
| Supply Voltage | 5 V ± 10% - eliminates need for dedicated programming voltage rails; compatible with standard 5V logic systems. |
| Operating Temperature | -40°C to +85°C - certified for industrial environments including factory automation and outdoor telemetry units. |
| Standby Current | 300 µA (CMOS) - reduces power consumption during idle states in battery-backed or energy-sensitive systems. |
Pinout & Package
AT29C256-12PI is available in 28-pin PDIP (28P6) package. Pin 1 is index corner; pins 1–14 and 15–28 occupy opposite sides. Pins 1 and 17 are no-connect (NC) in PLCC variant but not applicable here - this PDIP variant has full 28-pin functional mapping.
| 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; latched on WE/CE falling edge for byte loads; outputs high-Z when CE or OE high. |
| CE | Chip Enable | Active-low chip select; must be low with OE low and WE high for valid read; inhibits writes if held high. |
| OE | Output Enable | Active-low output control; disables outputs (high-Z) when high; required high during programming cycles. |
| WE | Write Enable | Active-low write strobe; initiates byte loads and triggers internal program/erase timers when CE also low. |
| VCC | Power Supply | +5 V ± 10% main supply; powers core logic and I/O buffers; VCC sense circuitry prevents writes below ~3.8 V. |
| GND | Ground Reference | Signal and power return path; decoupling capacitor required near VCC pin for stable operation. |
Key Features
| Feature | Design Value |
|---|---|
| 5V-only reprogramming | Eliminates need for external 12V programming supply - simplifies PCB layout and reduces BOM cost in industrial control modules. |
| Internal page latching | 64-byte data and address latched internally during load phase - frees system bus for concurrent operations during programming latency. |
| DATA polling (I/O7) | Complement-to-data response on I/O7 signals end-of-program - enables deterministic polling without timer overhead or external status lines. |
| Toggle-bit detection (I/O6) | I/O6 toggles during active program/erase - provides alternate, address-agnostic method to monitor completion in interrupt-driven firmware. |
| Software data protection | Three-byte unlock sequence (5555h/2AAAh/5555h + A0h or 80h) prevents accidental writes - critical for field-upgradable devices with unattended operation. |
Applications
| Industrial PLC Firmware Storage | Legacy Embedded Controller Boot Memory |
|---|---|
Use Scenario: Storing ladder logic programs and I/O configuration tables in programmable logic controllers deployed in manufacturing lines. IC Role / Device Role / Timing Role: Nonvolatile boot and runtime code storage; accessed as memory-mapped device on 8-bit parallel bus with 120 ns timing compliance. Use Value: Enables field firmware updates without hardware rework; 10,000-cycle endurance ensures multi-year service life under periodic revision schedules. | Use Scenario: Holding boot loader and calibration data in older medical diagnostic instruments using Z80 or 8051-based architectures. IC Role / Device Role / Timing Role: Drop-in replacement for obsolete 27C256 EPROMs; retains same pinout and 5V interface while adding in-system reprogrammability. Use Value: Eliminates UV eraser dependency and socket programming; software protection prevents corruption during power cycling in clinical environments. |
| Automated Test Equipment (ATE) Configuration | Point-of-Sale Terminal Parameter Storage |
Use Scenario: Storing test pattern sets and fixture-specific calibration offsets in semiconductor ATE handlers operating in factory cleanrooms. IC Role / Device Role / Timing Role: Static memory-mapped configuration store; accessed during initialization and test setup phases with guaranteed 120 ns read latency. Use Value: Supports rapid reconfiguration between product families; hardware VCC-sense protection prevents spurious writes during brown-out conditions. | Use Scenario: Retaining tax rate tables, language packs, and transaction log history in retail POS terminals installed in remote locations. IC Role / Device Role / Timing Role: Persistent parameter storage accessed via microcontroller's external memory interface; programmed via serial bootloader using page-write commands. Use Value: Enables remote firmware and regulatory updates over dial-up or cellular links; 300 µA standby current extends backup battery life during power outages. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar Flash memory applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AT29C256-12JI | Same die and timing, but in 32-lead PLCC (32J) package instead of 28-pin PDIP; includes NC pins at positions 1 and 17. | Requires different PCB footprint and socket; better thermal dissipation and higher vibration resistance than PDIP. | Select AT29C256-12JI for new board designs needing surface-mount reliability or improved thermal performance. |
| AT29C256-12TI | Identical electrical specs and timing, packaged in 28-lead TSOP (28T); thinner profile and smaller footprint than PDIP. | Suitable for space-constrained applications like handheld testers or compact I/O modules; no through-hole mounting. | Choose AT29C256-12TI when board real estate is limited and reflow assembly is preferred over through-hole. |
Compared with AT29C256-12PI, the AT29C256-12JI offers enhanced mechanical robustness in PLCC form, while AT29C256-12TI provides superior density and thermal profile in TSOP - both retain identical 120 ns access, 10 ms page programming, and software/hardware protection features for seamless functional substitution.
Availability
AT29C256-12PI is available at Aetrix Electronics and suitable for industrial control systems, legacy embedded instrumentation, and automated test equipment requiring stable component supply and long-term obsolescence management.
Supply support for AT29C256-12PI 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, designed high-reliability nonvolatile memory and microcontroller solutions for industrial, automotive, and communications markets.
The AT29C256 product line delivers 5V-only Flash memory optimized for in-system reprogrammability in legacy 8-bit and 16-bit embedded platforms where simplicity, robustness, and long-lifecycle support are essential.
FAQ
What is the maximum operating temperature range for the AT29C256-12PI?
The AT29C256-12PI is rated for industrial temperature operation from -40°C to +85°C. This specification is confirmed in the DC and AC Operating Range table of the official Atmel datasheet (Rev. 0046O–FLASH–06/02), where the "-12" speed grade and "-PI" suffix explicitly denote the industrial temperature range. The device maintains full functionality-including 120 ns read access and 10 ms page programming-across this entire range.
Does the AT29C256-12PI require high-voltage programming signals?
No, the AT29C256-12PI does not require high-voltage programming signals. As stated in the Features section, it supports "5-volt Only Reprogramming" with internal voltage generation. Programming is initiated using standard 5V logic levels on CE, WE, and OE, combined with specific address/data sequences (e.g., AAh/55h/A0h unlock). The hardware protection circuitry actively inhibits programming if VCC falls below ~3.8 V, ensuring safe operation within a single 5V supply rail.
How is programming status detected on the AT29C256-12PI?
Programming status on the AT29C256-12PI is detected using two hardware methods: DATA polling on I/O7 and the Toggle Bit on I/O6. During programming, reading the last loaded byte returns the complement of the data on I/O7; when complete, true data appears. Simultaneously, I/O6 toggles between 0 and 1 until completion, then stabilizes. Both mechanisms are documented in the "DATA Polling" and "TOGGLE BIT" sections of the datasheet and require no external components or timers.
What package type is used by the AT29C256-12PI?
The AT29C256-12PI uses a 28-lead plastic dual inline package (PDIP), designated as package code "28P6" in the Ordering Information table. This is a 0.600" wide through-hole package with standard DIP pin spacing (2.54 mm). The "-PI" suffix specifically denotes the industrial temperature grade in PDIP packaging, distinguishing it from PLCC ("JC") and TSOP ("TC") variants listed alongside it in the same datasheet revision.
Can the AT29C256-12PI be used as a direct replacement for the AT27C256 EPROM?
Yes, the AT29C256-12PI is functionally and pin-compatible with the AT27C256 EPROM in read mode and shares identical 28-pin PDIP pinout, address/data bus structure, and CE/OE/WE control signaling. However, unlike the EPROM, the AT29C256-12PI supports in-system reprogramming via software command sequences and requires no UV erasure. Its 120 ns access time matches common AT27C256-12 variants, making it a drop-in upgrade path for field-serviceable legacy systems.
AT29C256-12PI 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:
- 120 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
AT29C256-12PI FAQ
1.How can I place an order for AT29C256-12PI through Aetrix?
Please submit a Request for Quotation (RFQ) for AT29C256-12PI 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 AT29C256-12PI reliable?
The price and inventory of AT29C256-12PI are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AT29C256-12PI is usually 5 days.
3.What payment methods are accepted for AT29C256-12PI?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AT29C256-12PI transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AT29C256-12PI?
AT29C256-12PI orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AT29C256-12PI 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 AT29C256-12PI?
For technical support, including AT29C256-12PI datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AT29C256-12PI requirements.
6.How does Aetrix verify that AT29C256-12PI is sourced from the original manufacturer or authorized distributors?
All AT29C256-12PI 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 AT29C256-12PI meets industry standards.
7.What is the process for return or replacement of AT29C256-12PI?
All AT29C256-12PI units undergo pre-shipment inspection (PSI). If there is an issue with AT29C256-12PI, 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 AT29C256-12PI part is unused and in its original packaging.
Return procedure for AT29C256-12PI:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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