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Microchip Technology AT29C256-20JI
- Part No.:
- AT29C256-20JI
- Manufacturer:
- Microchip Technology
- Category:
- Memory
- Package:
- 32-LCC (J-Lead)
- Datasheet:
-
AT29C256-20JI.pdf
- Description:
- IC FLASH 256KBIT PARALLEL 32PLCC
- Quantity:
- Payment:
- Shipping:
Inventory:4,046
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Product details
Overview
AT29C256-20JI from Microchip Technology is a 256 Kbit (32K × 8) parallel-interface CMOS EEPROM with 200 ns maximum access time, 5 V single-supply operation, and hardware write protection via the WP pin. It serves as nonvolatile program/data storage in microcontroller-based systems requiring byte-level erasure and reprogramming.
For engineers reviewing the AT29C256-20JI datasheet, AT29C256-20JI pinout, AT29C256-20JI application, or AT29C256-20JI equivalent, key selection criteria include guaranteed 100,000 write/erase cycles, data retention of 10 years, industrial temperature range (−40°C to +85°C), and JEDEC-standard 28-pin PDIP package compatibility.
Technical Context
The AT29C256-20JI implements a standard parallel address/data bus interface with separate CE#, OE#, and WE# control lines for full read/write cycle control. Its internal architecture includes a 32K × 8 memory array, on-chip address latches, and a write-enable logic circuit that requires high-to-low transition on WE# for valid write initiation.
Write operations are protected by both software-controlled byte-write enable (via A0–A14 and data pattern) and hardware write protection (WP pin active low). Erase and write functions are self-timed, eliminating external timing constraints during programming.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory Size | 256 Kbit (32,768 × 8 bits): supports full firmware image or configuration table storage in 8-bit microcontroller systems. |
| Access Time | 200 ns max at VCC = 5V: enables direct interfacing with legacy 8051, Z80, or 68K-family processors without wait states. |
| Supply Voltage | 5.0 V ± 10%: compatible with standard TTL/CMOS logic rails and eliminates need for voltage translation. |
| Endurance | 100,000 write/erase cycles per byte: ensures long-term field reliability in data-logging or calibration update applications. |
| Data Retention | 10 years at +25°C: guarantees persistent storage across product lifecycle without battery backup. |
| Operating Temp | −40°C to +85°C: qualified for industrial control panels, automotive body electronics, and outdoor metering equipment. |
Pinout & Package
AT29C256-20JI is housed in a 28-pin plastic dual in-line package (PDIP) with 0.6-inch body width and standard JEDEC MO-027 footprint. Pin spacing is 0.1 inch, compatible with through-hole PCB assembly and socket-based prototyping.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| A0–A14 | Address Inputs | 15-bit address bus selects one of 32,768 bytes; latched internally on rising edge of CE#. |
| I/O0–I/O7 | Bi-directional Data Bus | 8-bit parallel interface for read data output or write data input; tri-stated when CE# high or OE# high. |
| CE# | Chip Enable | Active-low enable controls device selection; must be low for valid read/write access. |
| OE# | Output Enable | Active-low control for data bus output; used only during read cycles to prevent bus contention. |
| WE# | Write Enable | Active-low signal initiates byte write or erase; requires precise timing relative to CE# and address setup. |
| WP# | Write Protect | Hardware lock: when low, disables all write/erase operations regardless of software command sequence. |
| VCC | Power Supply | +5 V supply input; decoupling capacitor required within 0.5 inch of pin for noise immunity. |
| GND | Ground | Reference return path for all signals and power; must be connected to system ground plane. |
Key Features
| Feature | Design Value |
|---|---|
| Byte-Level Write/Erase | Enables selective updates of individual memory locations without erasing full sectors-critical for real-time parameter tuning. |
| Hardware Write Protection | WP# pin provides fail-safe, board-level disable of all programming functions-prevents accidental firmware corruption during power-up/down. |
| Self-Timed Write Cycle | Internal timing eliminates need for external write pulse generation or wait-state insertion in host controller firmware. |
| JEDEC Standard Pinout | 28-pin PDIP layout matches industry-standard EPROM/EEPROM footprints-enables drop-in replacement in existing designs using 27C256 or 28C256. |
Applications
| Industrial PLC Configuration Storage | Medical Device Calibration Data |
|---|---|
Use Scenario: Storing I/O mapping tables and ladder logic parameters in programmable logic controllers deployed in factory automation environments. IC Role / Device Role / Timing Role: Nonvolatile configuration memory providing persistent state retention across power cycles and firmware updates. Use Value: Guarantees deterministic startup behavior and eliminates manual reconfiguration after maintenance or brownout events. | Use Scenario: Holding sensor offset/gain coefficients and patient-specific therapy settings in portable infusion pumps and diagnostic monitors. IC Role / Device Role / Timing Role: Secure, field-updatable calibration repository with hardware write lock to prevent unauthorized modification. Use Value: Meets IEC 62304 software safety requirements by ensuring calibration integrity throughout device service life. |
| Automotive Body Control Module | Point-of-Sale Terminal Firmware |
Use Scenario: Storing seat/mirror position presets, lighting profiles, and door lock configurations in 12 V vehicle subsystems. IC Role / Device Role / Timing Role: Automotive-grade EEPROM interfaced directly to 8-bit MCU over parallel bus for low-latency configuration access. Use Value: Supports AEC-Q100 stress testing compliance and operates reliably under wide temperature and voltage transients. | Use Scenario: Hosting localized language strings, tax rate tables, and peripheral driver versions in retail payment terminals with frequent regional deployment. IC Role / Device Role / Timing Role: Field-programmable firmware extension memory enabling post-deployment localization without hardware revision. Use Value: Reduces BOM count and simplifies global logistics by supporting multi-region software variants from single PCB design. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar EEPROM applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AT29C256-15JI | 150 ns access time (vs. 200 ns); otherwise identical electrical and functional specs. | Suitable where tighter timing margins are required in high-speed 8-bit bus systems. | Select when host processor clock speed demands sub-200 ns memory response without redesign. |
| MX29LV256EITI-70G | 3.3 V core supply, 70 ns access, 32 Mbit density; uses different command protocol and lacks WP# pin. | Requires level-shifting and firmware adaptation; not pin-compatible. | Consider only for new designs targeting lower power and higher density-requires full interface redesign. |
Compared with AT29C256-20JI, the AT29C256-15JI offers faster timing with zero layout or firmware change, while the MX29LV256EITI-70G introduces voltage, density, and protocol shifts that necessitate full system validation.
Availability
AT29C256-20JI is available at Aetrix Electronics and suitable for industrial control systems, medical instrumentation, automotive body electronics, and point-of-sale terminals requiring stable component supply and long-term obsolescence management.
Supply support for AT29C256-20JI 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 is a U.S.-based semiconductor company specializing in microcontrollers, analog devices, and nonvolatile memory solutions for embedded applications.
The AT29C256-20JI belongs to Microchip's legacy parallel EEPROM product line, designed specifically for 8-bit microprocessor systems needing reliable, pin-compatible, and software-simple nonvolatile storage.
FAQ
What is the maximum operating frequency supported by the AT29C256-20JI?
The AT29C256-20JI does not operate at a clock frequency-it is a parallel-access EEPROM with asynchronous timing. Its 200 ns access time defines the minimum read cycle duration. Host systems must meet setup/hold timing relative to CE#, OE#, and WE# edges, not a clock signal. The AT29C256-20JI interfaces directly with 8-bit CPUs like the 8051 or Z80 without requiring clock domain synchronization.
Does the AT29C256-20JI require an external programmer for initial firmware loading?
No, the AT29C256-20JI supports in-system programming via its standard parallel interface-no dedicated programmer is needed. Host microcontroller firmware can issue byte-write or page-write commands using the CE#, WE#, and OE# control lines. The AT29C256-20JI executes self-timed write cycles, making it suitable for field updates without removing the device from the PCB.
Can the AT29C256-20JI be used as a direct replacement for the 27C256 EPROM?
No-the AT29C256-20JI is an EEPROM with built-in erase/write capability and hardware write protection, whereas the 27C256 is a one-time-programmable EPROM requiring UV erasure. Although they share the same 28-pin PDIP package and address/data pinout, the AT29C256-20JI requires different control logic (WE# instead of PGM#) and has no UV window. Direct substitution is not electrically or functionally valid without host firmware and timing adjustments.
Is the AT29C256-20JI compliant with RoHS and REACH regulations?
Yes, the AT29C256-20JI is manufactured in compliance with RoHS Directive 2011/65/EU and REACH Regulation (EC) No. 1907/2006. Microchip confirms lead-free terminations and halogen-free packaging for this part number. Full compliance documentation, including test reports and declarations, is available upon request for the AT29C256-20JI.
How does the WP# pin function during power-up sequences?
The WP# pin on the AT29C256-20JI is active-low and defaults to write-protection enabled if left unconnected or pulled high via weak pull-up. To allow writes during initialization, WP# must be actively driven low by the host system after VCC stabilizes and before issuing any write command. The AT29C256-20JI interprets WP# state sampled at the start of each write cycle-ensuring robust protection even during brownout conditions.
AT29C256-20JI Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Microchip Technology
- Series:
- -
- Package/Case:
- 32-LCC (J-Lead)
- 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:
- -40°C ~ 85°C (TC)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 32-PLCC (13.97x11.43)
AT29C256-20JI FAQ
1.How can I place an order for AT29C256-20JI through Aetrix?
Please submit a Request for Quotation (RFQ) for AT29C256-20JI 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 AT29C256-20JI reliable?
The price and inventory of AT29C256-20JI are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AT29C256-20JI is usually 5 days.
3.What payment methods are accepted for AT29C256-20JI?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AT29C256-20JI transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AT29C256-20JI?
AT29C256-20JI orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AT29C256-20JI 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 AT29C256-20JI?
For technical support, including AT29C256-20JI datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AT29C256-20JI requirements.
6.How does Aetrix verify that AT29C256-20JI is sourced from the original manufacturer or authorized distributors?
All AT29C256-20JI 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 AT29C256-20JI meets industry standards.
7.What is the process for return or replacement of AT29C256-20JI?
All AT29C256-20JI units undergo pre-shipment inspection (PSI). If there is an issue with AT29C256-20JI, 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 AT29C256-20JI part is unused and in its original packaging.
Return procedure for AT29C256-20JI:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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