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Microchip Technology AT29C256-70PC
- Part No.:
- AT29C256-70PC
- Manufacturer:
- Microchip Technology
- Category:
- Memory
- Package:
- 28-DIP (0.600", 15.24mm)
- Datasheet:
-
AT29C256-70PC.pdf
- Description:
- IC FLASH 256KBIT PARALLEL 28DIP
- Quantity:
- Payment:
- Shipping:
Inventory:3,635
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Product details
Overview
AT29C256-70PC from Atmel is a 256 Kbit (32K × 8) 5V-only Flash memory IC used for nonvolatile program/data storage in embedded microcontroller systems, boot code storage, and firmware update modules. It delivers 70 ns read access time, supports page programming of 64 bytes per cycle, and operates across commercial temperature range (0°C to 70°C) in a 28-pin PDIP package.
For engineers reviewing the AT29C256-70PC datasheet, AT29C256-70PC pinout, AT29C256-70PC application, or AT29C256-70PC equivalent, key selection criteria include 5V-only reprogramming compatibility, DATA polling and TOGGLE bit end-of-write detection, hardware/software data protection, and PLCC/PDIP/TSOP package interchangeability within the AT29C256 family.
Technical Context
The AT29C256-70PC implements a page-based Flash architecture with internal address and data latches for 64-byte writes, eliminating external buffering. Its dual-line chip enable (CE) and output enable (OE) control enables bus contention avoidance during mixed read/write operations in shared-memory systems.
Programming uses a six-byte software command sequence for chip erase and data protection activation; hardware safeguards include VCC sense (<3.8 V inhibit), 5 ms power-on delay, and noise filtering on WE/CE inputs. Data integrity is confirmed via I/O7 DATA polling or I/O6 toggle-bit monitoring during write cycles.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory Size | 256 Kbit (32,768 × 8), sufficient for full boot loader + configuration tables in 8-bit MCU systems |
| Read Access Time | 70 ns - enables direct execution from Flash in timing-critical 5 MHz Z80/8051-based designs |
| Page Program Time | 10 ms per 64-byte page - allows background firmware updates without system halt |
| VCC Supply | 5 V ± 10% - eliminates need for dedicated programming voltage regulators |
| Endurance | >10,000 write/erase cycles - supports field-upgradable firmware with multi-year service life |
| Standby Current | 300 µA CMOS - suitable for battery-backed applications requiring low quiescent power |
| Operating Temp | 0°C to 70°C - validated for commercial-grade industrial control panels and instrumentation |
Pinout & Package
AT29C256-70PC is packaged in a 28-pin Plastic Dual Inline Package (PDIP), 0.600" wide, with through-hole mounting and JEDEC MS-011 AB compliance. Pin 1 is index-marked; pins 1–14 and 15–28 are arranged on opposing sides.
| 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 | CMOS/TTL-compatible 8-bit data path; carries latched program data or read output |
| CE | Chip Enable | Active-low global device select; must be low for read, program, or erase operations |
| OE | Output Enable | Active-low output gate control; high during programming to disable outputs and prevent bus conflict |
| WE | Write Enable | Active-low control for byte load and page programming initiation; synchronized with CE for timing validation |
| VCC | Power Supply | +5 V ± 10% main supply; powers core logic and Flash array |
| GND | Ground Reference | Signal and power return; decoupling capacitor required at pin per layout guidelines |
Key Features
| Feature | Design Value |
|---|---|
| 5V-only reprogramming | Eliminates high-voltage charge pump circuitry, reducing BOM count and PCB area in legacy 5V systems |
| DATA polling on I/O7 | Enables real-time write completion detection without timer overhead or interrupt latency in MCU firmware |
| Software data protection | Three-command unlock sequence prevents accidental writes during power transitions or noise events |
| Hardware VCC sense | Automatically inhibits programming if supply drops below 3.8 V, preventing partial writes and data corruption |
| Toggle-bit status on I/O6 | Provides asynchronous, non-intrusive write progress monitoring compatible with any host controller |
Applications
| Industrial PLC Firmware Storage | Legacy PC BIOS Backup Memory |
|---|---|
Use Scenario: Storing ladder logic programs and I/O mapping tables in programmable logic controllers with infrequent field updates. IC Role / Device Role / Timing Role: Nonvolatile boot and configuration memory interfaced directly to 8051 or Z80 CPU address/data buses. Use Value: 70 ns access time ensures deterministic scan-cycle timing; 10,000-cycle endurance supports 5+ years of maintenance updates. | Use Scenario: Retaining BIOS recovery images and hardware configuration settings in desktop motherboards using ISA or LPC interfaces. IC Role / Device Role / Timing Role: Secondary firmware repository accessed only during POST or recovery mode, not during runtime. Use Value: Software chip erase (6-byte command) enables safe BIOS rollback; 300 µA standby current minimizes battery drain on CMOS RAM backup. |
| Embedded Instrumentation Calibration Data | Point-of-Sale Terminal Application Code |
Use Scenario: Holding factory-calibrated sensor coefficients and linearization tables in handheld multimeters and oscilloscopes. IC Role / Device Role / Timing Role: Read-mostly storage mapped into microcontroller memory space; updated only during calibration service. Use Value: Hardware data protection prevents corruption during ESD events near test jacks; 5V-only operation matches legacy analog front-end supplies. | Use Scenario: Hosting application firmware and localized UI strings in retail POS terminals with modular upgrade capability. IC Role / Device Role / Timing Role: In-system programmable code memory enabling over-the-air or USB-based firmware patches. Use Value: Page programming (64-byte granularity) allows patching individual function modules without full image reload; PDIP package simplifies manual rework in low-volume production. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar Flash memory applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AM29LV256M-70EC | 3.3 V core with 5 V I/O tolerance; 70 ns read; 100,000-cycle endurance | Requires level-shifting in pure 5 V systems; suited for mixed-voltage designs migrating toward lower power | Select when upgrading to 3.3 V infrastructure while retaining 5 V interface compatibility |
| SST39VF256A-70-4C-NHE | 3.3 V supply; 70 ns read; 100,000-cycle endurance; no hardware VCC sense | Lacks built-in VCC brown-out protection; requires external supervisor IC for robust power-fail handling | Prefer for new 3.3 V designs where cost-per-bit and endurance outweigh legacy 5 V compatibility |
Compared with AM29LV256M-70EC and SST39VF256A-70-4C-NHE, the AT29C256-70PC offers native 5 V operation and integrated hardware data protection ideal for retrofitting legacy systems, whereas alternatives prioritize higher endurance and lower voltage at the expense of direct drop-in replacement in 5 V-only environments.
Availability
AT29C256-70PC is available at Aetrix Electronics and suitable for industrial PLC firmware storage, legacy PC BIOS backup, embedded instrumentation calibration data, and point-of-sale terminal application code requiring stable component supply across extended product lifecycles.
Supply support for AT29C256-70PC 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 for industrial, automotive, and consumer applications.
The AT29C256 belongs to Atmel's legacy 5V Flash memory product line, designed specifically for in-system reprogrammability in cost-sensitive, voltage-stable 5 V embedded systems without requiring external high-voltage programming circuitry.
FAQ
What is the maximum operating frequency supported by AT29C256-70PC for reliable read access?
The AT29C256-70PC guarantees 70 ns read access time, enabling reliable operation up to 5 MHz bus frequency in static memory interfaces. This timing is validated under VCC = 5 V ± 10% and ambient temperature 0°C to 70°C, matching standard 8051 and Z80 system clocks without wait-state insertion. The AT29C256-70PC does not specify a maximum clock frequency independent of access timing; design margin should account for board trace delays and loading.
Does AT29C256-70PC support true random-access byte programming, or is page-level writing mandatory?
AT29C256-70PC requires page-level programming: all 64 bytes of a selected page must be loaded before internal erase-and-program execution begins. Individual byte modification is not supported - changing one byte necessitates reloading the full 64-byte page with updated data. This constraint is inherent to the device's Flash architecture and is documented in the "PROGRAM" section of the AT29C256-70PC datasheet.
How is software data protection enabled and disabled on AT29C256-70PC?
Software data protection on AT29C256-70PC is enabled via a three-command sequence: write 0xAA to address 0x5555, then 0x55 to 0x2AAA, then 0xA0 to 0x5555. Disabling requires six commands: 0xAA→0x5555, 0x55→0x2AAA, 0x80→0x5555, then repeat the first three. Both sequences must comply with AT29C256-70PC page programming timing, and protection persists across power cycles until explicitly disabled.
Can AT29C256-70PC be used in industrial temperature applications (-40°C to +85°C)?
No - AT29C256-70PC is rated only for commercial temperature range (0°C to +70°C). For industrial operation, the pin-compatible AT29C256-70PI (PDIP) or AT29C256-70TI (TSOP) variants must be selected. These share identical AC/DC specifications and programming behavior but are screened and qualified across -40°C to +85°C per the AT29C256 ordering table.
What package types are available for AT29C256-70PC, and are they pin-compatible?
AT29C256-70PC is specified exclusively in the 28-pin PDIP (28P6) package. Other members of the AT29C256-70x family include PLCC (32J) and TSOP (28T) variants (e.g., AT29C256-70JC, AT29C256-70TC), but these are not pin-compatible with AT29C256-70PC due to differing pin counts and layouts. Direct substitution requires PCB redesign.
AT29C256-70PC 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:
- 70 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
AT29C256-70PC FAQ
1.How can I place an order for AT29C256-70PC through Aetrix?
Please submit a Request for Quotation (RFQ) for AT29C256-70PC 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 AT29C256-70PC reliable?
The price and inventory of AT29C256-70PC are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AT29C256-70PC is usually 5 days.
3.What payment methods are accepted for AT29C256-70PC?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AT29C256-70PC transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AT29C256-70PC?
AT29C256-70PC orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AT29C256-70PC 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 AT29C256-70PC?
For technical support, including AT29C256-70PC datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AT29C256-70PC requirements.
6.How does Aetrix verify that AT29C256-70PC is sourced from the original manufacturer or authorized distributors?
All AT29C256-70PC 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 AT29C256-70PC meets industry standards.
7.What is the process for return or replacement of AT29C256-70PC?
All AT29C256-70PC units undergo pre-shipment inspection (PSI). If there is an issue with AT29C256-70PC, 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 AT29C256-70PC part is unused and in its original packaging.
Return procedure for AT29C256-70PC:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
AT29C256-70PC Tags
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