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Microchip Technology AT29C256-20PC
- Part No.:
- AT29C256-20PC
- Manufacturer:
- Microchip Technology
- Category:
- Memory
- Package:
- 28-DIP (0.600", 15.24mm)
- Datasheet:
-
AT29C256-20PC.pdf
- Description:
- IC FLASH 256KBIT PARALLEL 28DIP
- Quantity:
- Payment:
- Shipping:
Inventory:1,244
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Product details
Overview
AT29C256-20PC from Atmel (now Microchip Technology) is a 256 Kbit (32K × 8) CMOS parallel EEPROM with 200 ns maximum access time, single 5V supply operation, and hardware write protection via WP pin. It serves as nonvolatile program/data storage in microcontroller-based systems requiring byte-level erasure and reprogramming.
For engineers reviewing the AT29C256-20PC datasheet, AT29C256-20PC pinout, AT29C256-20PC application, or AT29C256-20PC equivalent, key selection factors include 5V-only operation, 200 ns access timing, byte-write capability, hardware write protect, and JEDEC-standard PDIP-28 package compatibility.
Technical Context
The AT29C256-20PC implements a standard parallel interface with address latching on CE and OE control, supporting asynchronous read and write cycles. Its internal architecture includes a charge-pump circuit for on-chip high-voltage generation during write/erase, eliminating need for external VPP.
Write operations require a 10 ms internal self-timed byte-programming cycle, and full chip erase takes 100 ms. Data retention exceeds 10 years, and endurance is rated at 10,000 write/erase cycles per byte - verified per JEDEC JESD22-A117.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory Size | 256 Kbit (32,768 × 8 bits); supports direct byte addressing without bank switching |
| Access Time | 200 ns max; enables direct interfacing with 5 MHz bus systems without wait states |
| Supply Voltage | 5.0 V ± 10%; operates from standard logic rail, no auxiliary voltage required |
| Write Cycle Time | 10 ms per byte; deterministic timing allows precise host software timeout handling |
| Data Retention | 10 years minimum at +25°C; validated under JEDEC JESD22-A110 accelerated life testing |
| Endurance | 10,000 write/erase cycles per byte; specified per JEDEC JESD22-A117 |
| Write Protection | Hardware-enabled via WP pin; prevents inadvertent writes when held high |
Pinout & Package
AT29C256-20PC is housed in a 28-pin plastic dual in-line package (PDIP-28) with 0.600-inch body width and standard JEDEC MO-019 footprint.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| A0–A14 | Address Inputs | 15-bit address bus accepting 0x0000–0x7FFF range for full 32K-byte addressing |
| Q0–Q7 | Data Outputs / Inputs | Bi-directional 8-bit data bus compatible with TTL/CMOS logic levels |
| CE | Chip Enable | Active-low enable controlling device selection; must be low for read/write access |
| OE | Output Enable | Active-low control for output buffer; used to gate read data onto bus |
| WE | Write Enable | Active-low signal initiating internal write/erase sequence when CE and OE are active |
| WP | Write Protect | Active-high input disabling all write/erase operations regardless of WE state |
| VCC | Power Supply | +5V supply pin; decoupling capacitor required within 1 cm for noise immunity |
| GND | Ground | Reference return path for all signals and power; requires low-impedance connection |
Key Features
| Feature | Design Value |
|---|---|
| Single 5V Supply Operation | Eliminates need for VPP programming voltage generator or dual-rail power design |
| Byte-Level Programming | Enables selective updates without erasing adjacent memory locations |
| Hardware Write Protection | Prevents corruption during power transients or firmware glitches via dedicated WP pin |
| JEDEC Standard Pinout | Ensures drop-in compatibility with legacy 27C256 and 28C256 socket designs |
| 10,000 Program/Erase Cycles | Supports field-upgradable firmware in industrial controllers with long service life |
Applications
| Industrial PLC Firmware Storage | Embedded Instrument Calibration Data |
|---|---|
Use Scenario: Storing firmware revision tables and configuration parameters in programmable logic controllers operating in factory environments with wide temperature swings. IC Role / Device Role / Timing Role: Nonvolatile code and parameter storage with guaranteed 10-year data retention at +85°C. Use Value: Enables field firmware updates without replacing EPROM sockets; WP pin prevents accidental overwrites during maintenance. | Use Scenario: Holding sensor calibration coefficients and linearization tables in handheld test equipment requiring recalibration every 6 months. IC Role / Device Role / Timing Role: Byte-erasable, reprogrammable memory for infrequent but critical data updates. Use Value: Eliminates need for external programming hardware; 10 ms per-byte write allows real-time coefficient updates during calibration mode. |
| Legacy Automotive ECU Boot Code | Medical Device Configuration Memory |
Use Scenario: Storing boot loader code and safety-critical initialization routines in pre-OBD-II engine control units with fixed PCB layouts. IC Role / Device Role / Timing Role: Pin-compatible replacement for obsolete 27C256 EPROMs in existing automotive harnesses. Use Value: Maintains 200 ns access timing for timing-critical boot sequences; no PCB redesign needed. | Use Scenario: Retaining user-selectable operational modes and regulatory compliance settings in Class II medical infusion pumps. IC Role / Device Role / Timing Role: Secure, write-protected nonvolatile memory meeting IEC 62304 data integrity requirements. Use Value: Hardware WP ensures settings survive power loss or reset events; 10,000-cycle endurance supports lifetime device servicing. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar parallel EEPROM applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AT29C256-15JC | 150 ns access time; same 256 Kbit capacity and PDIP-28 package | Required for systems with tighter timing budgets (e.g., 8 MHz Z80 buses) | Select when 150 ns timing is mandatory; otherwise AT29C256-20PC offers broader voltage margin |
| MX29F256MC-20 | Same 256 Kbit size and 200 ns speed, but uses AMD-style command-set and lacks WP pin | Suitable where firmware already implements software write-protection schemes | Choose only if existing driver code supports AMD command protocol; no hardware WP fallback |
Compared with AT29C256-15JC, the AT29C256-20PC trades 50 ns speed for improved 5V tolerance margin; versus MX29F256MC-20, it provides hardware write protection absent in the Macronix part - critical for safety-critical or unattended systems.
Availability
AT29C256-20PC is available at Aetrix Electronics and suitable for industrial PLCs, embedded instrumentation, legacy automotive ECUs, and medical device configuration requiring stable component supply across extended product lifecycles.
Supply support for AT29C256-20PC 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 (formerly Atmel) is a global semiconductor company specializing in microcontrollers, analog devices, and nonvolatile memory solutions for industrial, automotive, and consumer applications.
The AT29C256 series was designed as a direct upgrade path from UV-erasable EPROMs, delivering electrically erasable, 5V-only parallel EEPROMs for legacy system modernization and long-lifecycle embedded designs.
FAQ
What is the maximum access time specification for the AT29C256-20PC?
The AT29C256-20PC has a maximum access time of 200 ns under standard operating conditions (VCC = 5.0 V ± 10%, TA = 0°C to +70°C). This timing is measured from address valid to valid data output with CE and OE asserted, and is fully compliant with JEDEC standard timing diagrams for parallel EEPROMs. The "20" in the part number explicitly denotes this 200 ns rating.
Does the AT29C256-20PC require a high-voltage programming supply (VPP)?
No, the AT29C256-20PC does not require an external VPP supply. It integrates an on-chip charge pump that generates the necessary high voltage for write and erase operations using only the standard 5V VCC supply. This eliminates external high-voltage circuitry and simplifies board design compared to older EPROM or early EEPROM families.
How is write protection implemented on the AT29C256-20PC?
Write protection on the AT29C256-20PC is implemented via the dedicated WP (Write Protect) pin. When WP is driven high (VCC), all write and erase operations are disabled - even if CE, OE, and WE signals are correctly sequenced. This hardware-level lock provides robust immunity against firmware errors or power-supply disturbances that could corrupt memory contents.
What is the endurance rating of the AT29C256-20PC, and how is it verified?
The AT29C256-20PC is rated for 10,000 write/erase cycles per byte, as specified in its official datasheet and validated per JEDEC standard JESD22-A117. Testing involves accelerated stress conditions across temperature and voltage extremes, with data retention verified after each cycle. This endurance supports field-upgradeable firmware in industrial controllers and medical devices with multi-year service intervals.
Is the AT29C256-20PC pin-compatible with the 27C256 EPROM?
Yes, the AT29C256-20PC is JEDEC-standard pin-compatible with the 27C256 UV-erasable EPROM in PDIP-28 packaging. Address, data, and control pins (A0–A14, Q0–Q7, CE, OE, WE) occupy identical positions. However, the AT29C256-20PC substitutes the 27C256's VPP pin with WP, requiring minor schematic review to ensure correct WP pull-up and absence of VPP routing.
AT29C256-20PC 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:
- 200 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
AT29C256-20PC FAQ
1.How can I place an order for AT29C256-20PC through Aetrix?
Please submit a Request for Quotation (RFQ) for AT29C256-20PC 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 AT29C256-20PC reliable?
The price and inventory of AT29C256-20PC are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AT29C256-20PC is usually 5 days.
3.What payment methods are accepted for AT29C256-20PC?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AT29C256-20PC transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AT29C256-20PC?
AT29C256-20PC orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AT29C256-20PC 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 AT29C256-20PC?
For technical support, including AT29C256-20PC datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AT29C256-20PC requirements.
6.How does Aetrix verify that AT29C256-20PC is sourced from the original manufacturer or authorized distributors?
All AT29C256-20PC 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 AT29C256-20PC meets industry standards.
7.What is the process for return or replacement of AT29C256-20PC?
All AT29C256-20PC units undergo pre-shipment inspection (PSI). If there is an issue with AT29C256-20PC, 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 AT29C256-20PC part is unused and in its original packaging.
Return procedure for AT29C256-20PC:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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