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Microchip Technology AT29C256-90PC
- Part No.:
- AT29C256-90PC
- Manufacturer:
- Microchip Technology
- Category:
- Memory
- Package:
- 28-DIP (0.600", 15.24mm)
- Datasheet:
-
AT29C256-90PC.pdf
- Description:
- IC FLASH 256KBIT PARALLEL 28DIP
- Quantity:
- Payment:
- Shipping:
Inventory:4,820
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Product details
Overview
AT29C256-90PC from Atmel is a 5V-only, 256 Kbit (32K × 8) Flash memory IC designed for in-system reprogrammability in embedded control and firmware storage applications. It delivers 90 ns read access time, supports page programming of 64-byte blocks in 10 ms, and features hardware and software data protection. Its CMOS/TTL-compatible I/O and 300 µA standby current make it suitable for low-power industrial instrumentation and legacy microcontroller boot memory.
For engineers reviewing the AT29C256-90PC datasheet, AT29C256-90PC pinout, AT29C256-90PC application, or AT29C256-90PC equivalent, key selection criteria include verified 90 ns read timing, 5V ±10% supply tolerance, PLCC-32 package compatibility, DATA polling and toggle-bit program status detection, and software-controlled sector protection with 10,000-cycle endurance.
Technical Context
The AT29C256-90PC implements a nonvolatile Flash PEROM architecture with internal address/data latching for 64-byte page loads and autonomous erase-program sequencing controlled by an on-chip timer. It uses standard 5V-only command protocols-no high-voltage programming required-and supports both hardware-based VCC-sense inhibition and software-defined protection via three-byte unlock sequences.
Its operation relies on dual-line chip enable (CE) and output enable (OE) control for bus contention avoidance during reads, while write cycles are initiated by WE-controlled byte loads. Program completion is signaled either by DATA polling on I/O7 (complement-to-data transition) or toggling of I/O6, enabling deterministic host-side timing without fixed delays.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory Size | 256 Kbit (32,768 × 8), directly addressable as 15-bit address space (A0–A14) |
| Read Access Time | 90 ns max - defines minimum clock cycle for reliable read operations in 5 MHz+ systems |
| Page Program Time | 10 ms typical - enables burst loading of 64-byte firmware segments without external timing logic |
| VCC Supply Range | 5V ±10% - supports operation across wide input tolerances without regulation overhead |
| Standby Current | 300 µA CMOS - allows battery-backed retention in power-sensitive monitoring nodes |
| Endurance | >10,000 write/erase cycles per sector - sufficient for field-upgradable firmware with infrequent updates |
| Operating Temperature | 0°C to +70°C (Commercial) - validated for stable performance in office and lab environments |
Pinout & Package
AT29C256-90PC is packaged in a 32-lead Plastic J-Leaded Chip Carrier (PLCC-32), compliant with JEDEC MS-016 Variation AE. Pin 1 is marked by a corner chamfer; pins 1 and 17 are No Connect (NC). The package measures 12.4 mm × 14.9 mm × 3.5 mm (max height) with 1.27 mm lead pitch.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| A0–A14 | Address Inputs | 15-bit address bus; A6–A14 define page address during programming, A0–A5 select byte within 64-byte page |
| CE | Chip Enable | Active-low global enable; must be low for read, program, or erase; inhibits writes when high |
| OE | Output Enable | Active-low output control; high-Z state when high; required high during programming |
| WE | Write Enable | Active-low write strobe; controls byte load timing and initiates internal program sequence |
| I/O0–I/O7 | Bidirectional Data Bus | 8-bit data path; I/O7 used for DATA polling, I/O6 for toggle-bit status indication |
| VCC | Power Supply | +5V ±10% main supply; powers core logic and I/O buffers |
| GND | Ground | Reference return for all signals and power; pin 16 in PLCC-32 layout |
| NC / DC | No Connect / Don't Connect | Pins 1 and 17 - must remain unconnected; no internal bonding or function |
Key Features
| Feature | Design Value |
|---|---|
| 5V-only reprogramming | Eliminates need for +12V programming voltage rails, simplifying PCB power design and reducing BOM count |
| Internal page latching | 64-byte data and address held internally during program cycle, freeing system bus for concurrent tasks |
| Hardware data protection | VCC sense (disable below 3.8V), 5 ms power-on delay, and noise filtering (<15 ns pulses rejected) prevent spurious writes |
| Software data protection | Three-byte unlock sequence (AAh/55h/A0h) required before each program cycle; persists through power cycles |
| DATA polling & toggle bit | Dual asynchronous status methods (I/O7 complement, I/O6 toggle) allow flexible host polling without fixed timeouts |
Applications
| Industrial PLC Firmware Storage | Legacy Microcontroller Boot Memory |
|---|---|
|
Use Scenario: Storing firmware images and configuration parameters in programmable logic controllers deployed in factory automation environments. IC Role / Device Role / Timing Role: Nonvolatile boot ROM providing fast 90 ns instruction fetch capability and field-upgradable code storage. Use Value: Enables in-system firmware updates without removing the module; 10,000-cycle endurance supports decades of maintenance cycles under industrial temperature range. |
Use Scenario: Serving as primary boot memory for 8-bit microcontrollers (e.g., Intel 8051, Zilog Z8) in medical diagnostic equipment and test instruments. IC Role / Device Role / Timing Role: Static RAM-compatible read interface ensures drop-in replacement for older EPROMs without timing redesign. Use Value: 5V-only operation eliminates high-voltage programming circuitry; software protection prevents accidental corruption during power transitions. |
| Embedded Communication Module Code Storage | Automated Test Equipment (ATE) Pattern Memory |
|
Use Scenario: Holding protocol stack binaries and calibration tables in RS-485/Modbus gateways and IoT edge nodes. IC Role / Device Role / Timing Role: Page-programmable Flash memory supporting over-the-air (OTA) updates via serial interface with minimal host resource usage. Use Value: 64-byte page load reduces update latency versus byte-by-byte programming; DATA polling allows precise synchronization with host UART flow control. |
Use Scenario: Storing digital stimulus/response patterns in benchtop ATE systems requiring repeatable, deterministic vector playback. IC Role / Device Role / Timing Role: High-reliability nonvolatile memory delivering consistent 90 ns read timing for synchronized pattern generation clocks. Use Value: Low 300 µA standby current minimizes thermal drift in precision analog test fixtures; CMOS/TTL compatibility ensures direct interfacing with FPGA-based sequencers. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar Flash memory applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AM29LV256M-90EC | 3.3V core with 5V I/O tolerant; 90 ns read; 128K × 16 organization; requires VPP = 12V for sector erase | Designed for mixed-voltage systems; not 5V-only; lacks software data protection | Select if migrating to lower-power 3.3V designs and external high-voltage generation is acceptable |
| SST39VF256A-90-4C-NHE | 3.3V supply only; 90 ns read; 256K × 8; supports byte-write and block-erase; no hardware VCC sense | Requires level-shifting for 5V buses; lacks built-in power-fail write inhibition | Choose for new 3.3V designs where simplified power architecture outweighs loss of 5V-native robustness |
Compared with AM29LV256M-90EC and SST39VF256A-90-4C-NHE, the AT29C256-90PC offers unique 5V-only simplicity, integrated hardware write protection, and proven reliability in legacy 5V industrial systems-making it the preferred choice where backward compatibility and power-supply minimization are critical.
Availability
AT29C256-90PC is available at Aetrix Electronics and suitable for industrial PLC firmware storage, legacy microcontroller boot memory, and embedded communication module code storage requiring stable component supply and long-term obsolescence management.
Supply support for AT29C256-90PC 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 fabless semiconductor company specializing in microcontrollers, Flash memory, and secure authentication ICs, with a legacy of robust industrial-grade nonvolatile memory solutions.
The AT29C256 product line was engineered for cost-sensitive, 5V-based embedded systems needing field-upgradable firmware storage without high-voltage programming infrastructure-targeting industrial control, instrumentation, and legacy computing platforms.
FAQ
What is the maximum read access time specification for the AT29C256-90PC?
The AT29C256-90PC has a guaranteed maximum read access time of 90 ns under commercial temperature conditions (0°C to +70°C) and 5V ±10% supply. This parameter is fully characterized and tested per AC Read Characteristics in the official Atmel datasheet (Rev. 0046O–FLASH–06/02), ensuring deterministic timing for synchronous microcontroller interfaces.
Does the AT29C256-90PC require high-voltage programming signals?
No, the AT29C256-90PC operates with 5V-only programming-no external +12V or VPP signal is needed. All reprogramming commands (page program, chip erase, software protection enable/disable) are executed using standard 5V logic levels, making it compatible with simple 5V microcontroller GPIOs and eliminating dedicated high-voltage generator circuitry.
How does software data protection work on the AT29C256-90PC?
Software data protection on the AT29C256-90PC is enabled via a three-byte unlock sequence (0xAA to address 0x5555, 0x55 to 0x2AAA, then 0xA0 to 0x5555). Once activated, every subsequent program cycle must begin with this same sequence. The feature remains active across power cycles and prevents accidental writes unless the full command is issued-ensuring firmware integrity in noisy or unstable power environments.
What package type is used for the AT29C256-90PC?
The AT29C256-90PC uses a 32-lead Plastic J-Leaded Chip Carrier (PLCC-32) package, identified as "32J" in Atmel's ordering information. Pins 1 and 17 are designated No Connect (NC); the package conforms to JEDEC MS-016 Variation AE and measures 12.4 mm × 14.9 mm with 1.27 mm lead pitch-ideal for socketed industrial control modules.
Can the AT29C256-90PC be used in place of older EPROMs like the 27C256?
Yes, the AT29C256-90PC is pin-compatible with the 27C256 EPROM in PLCC-32 and PDIP-28 packages and shares identical address/data bus timing for read operations. However, unlike UV-erasable EPROMs, the AT29C256-90PC supports in-system electrical erasure and programming-enabling field updates without device removal or EPROM programmers.
AT29C256-90PC 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:
- 0°C ~ 70°C (TC)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 28-PDIP
AT29C256-90PC FAQ
1.How can I place an order for AT29C256-90PC through Aetrix?
Please submit a Request for Quotation (RFQ) for AT29C256-90PC 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 AT29C256-90PC reliable?
The price and inventory of AT29C256-90PC are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AT29C256-90PC is usually 5 days.
3.What payment methods are accepted for AT29C256-90PC?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AT29C256-90PC transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AT29C256-90PC?
AT29C256-90PC orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AT29C256-90PC 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 AT29C256-90PC?
For technical support, including AT29C256-90PC datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AT29C256-90PC requirements.
6.How does Aetrix verify that AT29C256-90PC is sourced from the original manufacturer or authorized distributors?
All AT29C256-90PC 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 AT29C256-90PC meets industry standards.
7.What is the process for return or replacement of AT29C256-90PC?
All AT29C256-90PC units undergo pre-shipment inspection (PSI). If there is an issue with AT29C256-90PC, 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 AT29C256-90PC part is unused and in its original packaging.
Return procedure for AT29C256-90PC:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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