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Microchip Technology AT29C256-12PC
- Part No.:
- AT29C256-12PC
- Manufacturer:
- Microchip Technology
- Category:
- Memory
- Package:
- 28-DIP (0.600", 15.24mm)
- Datasheet:
-
AT29C256-12PC.pdf
- Description:
- IC FLASH 256KBIT PARALLEL 28DIP
- Quantity:
- Payment:
- Shipping:
Inventory:3,029
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Product details
Overview
AT29C256-12PC 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, 64-byte page programming in 10 ms, and operates across commercial temperature range (0°C to 70°C) in a 28-pin PDIP package.
For engineers reviewing the AT29C256-12PC datasheet, AT29C256-12PC pinout, AT29C256-12PC application, or AT29C256-12PC equivalent, key selection considerations include its 5V-only operation, hardware/software data protection, DATA polling and toggle-bit programming status detection, and compatibility with standard SRAM-like bus interfaces.
Technical Context
The AT29C256-12PC 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 responds to CE/OE/WE timing sequences identical to SRAM, enabling drop-in replacement in legacy designs requiring nonvolatile storage.
It integrates dual data protection: hardware-level VCC sensing (<3.8V inhibit), noise filtering (<15 ns pulse rejection), and software-controlled lock via three-byte command sequence (AAh/55h/A0h). Programming status is verified using I/O7 DATA polling or I/O6 toggle-bit behavior-both accessible during active cycles without halting system operation.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory Density | 256 Kbit (32,768 × 8), sufficient for firmware boot code or configuration tables in microcontroller-based systems |
| Read Access Time | 120 ns max - meets timing requirements for 8 MHz Z80, 68K, or early ARM7 bus interfaces |
| Page Program Time | 10 ms per 64-byte page - enables efficient field updates without full-chip erasure |
| VCC Supply | 5V ±10% - eliminates need for dedicated programming voltage regulators |
| Active Current | 50 mA max at 5 MHz - compatible with standard 5V power rails in industrial controllers |
| Standby Current | 300 µA CMOS - supports low-power sleep modes in battery-backed applications |
| Endurance | >10,000 write/erase cycles per sector - suitable for infrequently updated calibration or logging data |
Pinout & Package
AT29C256-12PC is supplied in a 28-pin Plastic Dual Inline Package (PDIP), 0.600" wide, with through-hole mounting and industry-standard pin layout. Pin 1 is index-marked; pins 1–14 and 15–28 occupy opposite sides of the body.
| 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 |
| I/O0–I/O7 | Bidirectional Data Bus | 8-bit parallel interface compatible with 8051, Z80, and 68000 data buses; supports byte load and read operations |
| CE | Chip Enable | Active-low chip select; must be low for read or program cycles; high-Z output when asserted high |
| OE | Output Enable | Active-low output control; used with CE to prevent bus contention during reads |
| WE | Write Enable | Active-low signal initiating byte loads and page programming; timing-critical for 150 µs inter-byte window |
| VCC | Power Supply | +5V ±10% supply input; powers core logic and I/O drivers |
| GND | Ground Reference | Signal and power return path; decoupling capacitor required near VCC pin |
Key Features
| Feature | Design Value |
|---|---|
| 5V-only reprogramming | Eliminates need for +12V programming supply, simplifying power design and enabling direct MCU GPIO control |
| 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 | User-configurable lock via AAh/55h/A0h command sequence; persists across power cycles until explicitly disabled |
| DATA polling on I/O7 | Enables real-time program completion detection without external timers or interrupts |
| Toggle-bit status on I/O6 | Provides alternative asynchronous method to monitor programming/erase progress using any address location |
Applications
| Industrial PLC Firmware Storage | Legacy Embedded System Boot Memory |
|---|---|
Use Scenario: Storing ladder logic firmware and I/O mapping tables in programmable logic controllers with no external programming hardware. IC Role / Device Role / Timing Role: Nonvolatile boot ROM providing immediate code execution after power-up; accessed as SRAM-mapped memory during reset vector fetch. Use Value: 120 ns access time ensures zero-wait-state operation with 8 MHz 80C188EX CPUs; 10,000-cycle endurance accommodates quarterly firmware updates over 10+ year product life. | Use Scenario: Replacing obsolete EPROMs (e.g., 27C256) in medical diagnostic equipment where field upgrades are required but socket space is fixed. IC Role / Device Role / Timing Role: Pin-compatible Flash replacement for UV-erasable EPROMs; uses identical DIP-28 footprint and SRAM-like read protocol. Use Value: Eliminates UV eraser dependency and allows in-circuit reprogramming via existing JTAG or serial port; software protection prevents corruption during power loss during update. |
| Automotive Body Control Module Configuration | Point-of-Sale Terminal Parameter Storage |
Use Scenario: Holding vehicle-specific calibration data (e.g., door lock timing, mirror position offsets) in body control units subject to temperature cycling (-40°C to +85°C). IC Role / Device Role / Timing Role: Nonvolatile parameter store accessed during startup and runtime by 8-bit MCU; retains data across ignition cycles. Use Value: 300 µA standby current minimizes battery drain in parked vehicles; hardware VCC-sense protection prevents writes during engine cranking voltage sag. | Use Scenario: Storing tax rate tables, language packs, and receipt format templates in retail terminals deployed globally with regional compliance requirements. IC Role / Device Role / Timing Role: Field-upgradable configuration memory mapped into MCU address space; updated via RS-232 or USB-to-serial adapter. Use Value: Page programming enables partial updates without erasing pricing rules; software data protection prevents unauthorized modification of fiscal parameters. |
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, industrial temperature range (-40°C to +85°C); otherwise identical AC/DC specs and pinout | Required for automotive or outdoor deployment where ambient exceeds 70°C | Select AT29C256-12JI when operating environment exceeds commercial temperature limits |
| SST39SF200A-70-4C-NHE | 5V Flash with 70 ns access, 256 Kbit density, but uses different command set and lacks hardware VCC-sense protection | Requires firmware adaptation for write enable sequence; no built-in brown-out write inhibition | Choose SST39SF200A only if faster access is critical and system-level voltage monitoring is already implemented |
Compared with AT29C256-12PC, AT29C256-12JI extends thermal reliability without changing layout or firmware, while SST39SF200A-70-4C-NHE trades robustness for speed and demands additional software validation for safe reprogramming.
Availability
AT29C256-12PC is available at Aetrix Electronics and suitable for industrial control systems, legacy equipment repair, and point-of-sale terminal manufacturing requiring stable component supply and long-term obsolescence management.
Supply support for AT29C256-12PC 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, in-system programmable nonvolatile storage in 8-bit and 16-bit embedded systems where pin compatibility with EPROMs and simple 5V-only operation were critical.
FAQ
What is the maximum operating frequency supported by the AT29C256-12PC?
The AT29C256-12PC does not operate at a clock frequency like a microcontroller. Instead, it supports bus interface speeds up to 5 MHz (per ICC test condition), with read access time guaranteed at ≤120 ns. This enables reliable use with 8 MHz Z80 or 68000 systems running with one wait state, and zero-wait-state operation at lower frequencies such as 4 MHz or below. The device's timing is governed by CE/OE/WE setup/hold windows-not an internal clock.
Does the AT29C256-12PC require external high-voltage circuitry for programming?
No, the AT29C256-12PC requires only a single 5V ±10% supply for both read and programming operations. All reprogramming-including page writes and chip erase-is executed using standard 5V logic levels and specific software command sequences (e.g., AAh/55h/A0h). No external +12V or +21V programming voltage is needed, making AT29C256-12PC suitable for in-system updates via microcontroller GPIOs without auxiliary power rails.
How is programming completion detected on the AT29C256-12PC?
Programming completion on the AT29C256-12PC can be detected using two hardware-supported methods: DATA polling on I/O7 (complement of last written byte appears until completion) or toggle-bit monitoring on I/O6 (toggles between 0 and 1 during programming, then stabilizes). Both methods allow real-time status checking without halting the host processor or relying on fixed timeout delays. These features are intrinsic to the AT29C256-12PC design and require no external components.
Can the AT29C256-12PC be used as a direct replacement for the 27C256 EPROM?
Yes, the AT29C256-12PC is functionally and pinout-compatible with the 27C256 EPROM in DIP-28 packages, sharing identical address/data bus connections and CE/OE/WE control signals. However, unlike UV-erasable EPROMs, the AT29C256-12PC supports electrical in-system reprogramming and includes hardware/software write protection. No PCB changes are required, but firmware must implement the AT29C256-12PC's page-program command sequence instead of EPROM programming algorithms.
What is the purpose of the NC (No Connect) pins on the AT29C256-12PC PLCC variant, and do they apply to the PDIP version?
The NC (No Connect) pins referenced in the PLCC top view (pins 1 and 17) are specific to the 32-lead PLCC package (e.g., AT29C256-12JC) and do not exist on the AT29C256-12PC PDIP variant. The AT29C256-12PC uses a 28-pin PDIP with no NC pins - all 28 pins have defined functions (A0–A14, I/O0–I/O7, CE, OE, WE, VCC, GND). Therefore, pin 1 on AT29C256-12PC is A0 (not NC), and pin 28 is VCC, per the DIP top-view diagram in the datasheet.
AT29C256-12PC 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:
- 0°C ~ 70°C (TC)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 28-PDIP
AT29C256-12PC FAQ
1.How can I place an order for AT29C256-12PC through Aetrix?
Please submit a Request for Quotation (RFQ) for AT29C256-12PC 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 AT29C256-12PC reliable?
The price and inventory of AT29C256-12PC are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AT29C256-12PC is usually 5 days.
3.What payment methods are accepted for AT29C256-12PC?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AT29C256-12PC transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AT29C256-12PC?
AT29C256-12PC orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AT29C256-12PC 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 AT29C256-12PC?
For technical support, including AT29C256-12PC datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AT29C256-12PC requirements.
6.How does Aetrix verify that AT29C256-12PC is sourced from the original manufacturer or authorized distributors?
All AT29C256-12PC 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 AT29C256-12PC meets industry standards.
7.What is the process for return or replacement of AT29C256-12PC?
All AT29C256-12PC units undergo pre-shipment inspection (PSI). If there is an issue with AT29C256-12PC, 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 AT29C256-12PC part is unused and in its original packaging.
Return procedure for AT29C256-12PC:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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