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Microchip Technology AT27C256R-12PI
- Part No.:
- AT27C256R-12PI
- Manufacturer:
- Microchip Technology
- Category:
- Memory
- Package:
- 28-DIP (0.600", 15.24mm)
- Datasheet:
-
AT27C256R-12PI.pdf
- Description:
- IC EPROM 256KBIT PARALLEL 28DIP
- Quantity:
- Payment:
- Shipping:
Inventory:2,265
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Product details
Overview
AT27C256R-12PI from Microchip Technology (formerly Atmel) is a 32K × 8-bit one-time programmable EPROM optimized for industrial embedded firmware storage, featuring 120 ns maximum read access time, 5V ±10% single-supply operation, and JEDEC-standard 28-lead PDIP packaging. It delivers reliable nonvolatile code storage in microcontroller boot loaders and legacy control systems without requiring external wait states.
For engineers reviewing the AT27C256R-12PI datasheet, AT27C256R-12PI pinout, AT27C256R-12PI application, or AT27C256R-12PI equivalent, key selection criteria include verified 120 ns tACC timing at -40°C to +85°C, industrial-grade VPP programming voltage tolerance (12.0 V ±0.5 V), CMOS/TTL I/O compatibility, and Rapid™ programming algorithm support (100 µs/byte typical).
Technical Context
The AT27C256R-12PI implements a two-line control architecture with independent Chip Enable (CE) and Output Enable (OE) inputs, enabling precise bus contention management in multi-device memory systems. Its internal address decoder accepts A0–A14 (15-bit), supporting full 32K-byte addressing without external logic.
Programming relies on a dedicated VPP pin (12.0 V ±0.5 V) for OTP cell injection, while read operations use only VCC = 5V ±10%. The device integrates an electronic Product Identification Code accessible via A9 high-voltage mode and A0 toggling, allowing automated programmer recognition of manufacturer (0x1E) and device type (0x8C).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory Size | 32K × 8-bit (262,144 bits), sufficient for full microcontroller boot ROM or configuration tables |
| Read Access Time (tACC) | 120 ns max at industrial temperature (-40°C to +85°C), eliminates WAIT states in 8/16-bit CPU designs |
| VCC Supply | 5V ±10%, compatible with standard TTL/CMOS logic rails without regulation overhead |
| Standby Current (ISB1) | 100 µA max (CMOS CE input), enables low-power hold modes in battery-backed systems |
| Active Current (ICC) | 20 mA max at 5 MHz, supports sustained burst reads without thermal derating |
| VPP Programming Voltage | 12.0 V ±0.5 V, requires dedicated HV supply or charge pump during programming only |
| ESD Protection | 2,000V HBM, ensures robustness during manual handling and board assembly |
Pinout & Package
AT27C256R-12PI is packaged in a 28-lead, 0.600-inch wide plastic dual in-line package (PDIP), per JEDEC MS-011 AB standard. Pin 1 is index-marked; pins 1–14 and 15–28 are arranged across two parallel rows.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| A0–A14 | Address Inputs | 15-bit address bus interface; fully decoded internally to select one of 32,768 bytes |
| O0–O7 | Data Outputs | 8-bit bidirectional data bus outputs; high-impedance when OE or CE inactive |
| CE | Chip Enable | Primary device select; must be low for read or program access; controls power state transition |
| OE | Output Enable | Secondary output gate; allows shared bus operation without disabling chip power |
| VPP | Programming Voltage | 12 V input required only during OTP programming; must be applied simultaneously with or after VCC |
| VCC | Power Supply | +5 V ±10% main supply; powers all logic and memory arrays during read and standby |
| GND | Ground Reference | Signal and power return path; requires local 0.1 µF ceramic decoupling per device |
Key Features
| Feature | Design Value |
|---|---|
| Rapid™ Programming Algorithm | 100 µs/byte typical programming time with auto-verify loop, reducing production burn-in cycle time by >50% vs. legacy EPROMs |
| Integrated Product ID Code | Manufacturer (0x1E) and Device (0x8C) codes readable via A9=12V and A0 toggle, enabling plug-and-play programmer setup |
| Two-Line Control (CE/OE) | Independent enable signals allow flexible bus arbitration-OE can float while CE remains active for partial-bus isolation |
| Industrial Temperature Range | -40°C to +85°C operation validated across full AC/DC specs, suitable for factory automation and motor drives |
| CMOS/TTL I/O Compatibility | Input thresholds (VIL ≤0.8 V, VIH ≥2.0 V) and output drive (2.1 mA sink, -400 µA source) meet both logic families without level shifters |
Applications
| Industrial PLC Firmware Storage | Legacy Microcontroller Boot ROM |
|---|---|
Use Scenario: Storing ladder logic interpreter and I/O mapping tables in DIN-rail mounted programmable logic controllers operating continuously in factory environments. IC Role / Device Role / Timing Role: Nonvolatile boot memory providing deterministic 120 ns instruction fetch timing to 8051- or Z80-based CPU cores. Use Value: Eliminates reliance on slow serial EEPROM or unreliable battery-backed SRAM, ensuring cold-start reliability after power loss. | Use Scenario: Holding immutable startup code and hardware initialization routines in automotive engine control units (ECUs) built with obsolete 8-bit MCUs. IC Role / Device Role / Timing Role: OTP EPROM serving as primary boot vector memory, accessed directly by MCU address bus during reset sequence. Use Value: Guarantees firmware integrity against corruption-no accidental rewrites possible after programming, unlike flash-based alternatives. |
| Medical Device Configuration Memory | Test Equipment Calibration Data Storage |
Use Scenario: Retaining safety-critical calibration constants and operational limits in Class II medical infusion pumps certified to IEC 62304. IC Role / Device Role / Timing Role: Read-only configuration store accessed during power-up self-test; no write cycles permitted post-deployment. Use Value: Meets regulatory requirements for immutable parameter storage-no firmware update mechanism exists, preventing unauthorized modification. | Use Scenario: Preserving factory-trimmed ADC offset/gain coefficients and sensor linearization tables in benchtop multimeters and signal analyzers. IC Role / Device Role / Timing Role: Static lookup table memory mapped into test instrument's memory space for real-time correction during measurement cycles. Use Value: Enables high-accuracy measurements without recalibration-data survives 10+ years with zero bit-rot risk due to OTP structure. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar OTP EPROM applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AT27C256B-12PI | Same pinout and timing, but uses older Rapid programming algorithm (200 µs/byte typical); lacks integrated ID code | No automatic programmer recognition; requires manual algorithm selection | Select only if legacy programming hardware lacks ID-code detection capability |
| MX27C256-12PC | Functionally identical 32K×8 OTP EPROM, but rated only for commercial temp (0°C to 70°C); same 120 ns tACC | Not qualified for industrial ambient conditions; may fail under thermal cycling | Acceptable only in climate-controlled lab or office equipment-not for factory floor deployment |
Compared with AT27C256R-12PI, the AT27C256B-12PI sacrifices programmability speed and ID-code convenience for backward compatibility, while MX27C256-12PC trades industrial temperature qualification for lower cost-neither offers drop-in replacement assurance without thermal or programming workflow validation.
Availability
AT27C256R-12PI is available at Aetrix Electronics and suitable for industrial control systems, legacy embedded boot loaders, medical device configuration storage, and test equipment calibration data retention requiring stable component supply over extended product lifecycles.
Supply support for AT27C256R-12PI 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 acquired Atmel in 2016 and maintains full support for legacy Atmel memory products including the AT27C256R series.
The AT27C256R product line was designed specifically for industrial and automotive applications requiring guaranteed nonvolatile storage with zero rewrite risk, leveraging scaled CMOS process for low-power OTP reliability.
FAQ
What is the maximum operating temperature range for the AT27C256R-12PI?
The AT27C256R-12PI is specified for industrial temperature operation from -40°C to +85°C. This range is validated across all DC and AC parameters-including 120 ns read access time, 100 µA standby current, and 20 mA active current-and applies to both read and standby modes. The device does not support programming at temperature extremes; programming must occur at TA = 25°C ±5°C per datasheet Section 7.
Does the AT27C256R-12PI require a separate programming voltage during normal read operation?
No, the AT27C256R-12PI operates from a single 5V ±10% supply (VCC) during read mode. The VPP pin is only used during OTP programming and must be disconnected or held at VCC during read operations. Applying 12 V to VPP while reading will damage the device. The datasheet explicitly states VPP must be at VCC level for read/standby modes.
Can the AT27C256R-12PI be used as a direct replacement for the AT27C256R-12JC in a PLCC socket?
No, the AT27C256R-12PI uses a 28-lead PDIP package (28P6), while the AT27C256R-12JC uses a 32-lead PLCC package (32J). They have different pin counts, physical dimensions, and mounting methods. Interchange requires PCB redesign and socket replacement. Electrical functionality is identical, but mechanical fit is not compatible.
What decoupling capacitance is required for stable operation of the AT27C256R-12PI?
The AT27C256R-12PI requires a minimum 0.1 µF high-frequency ceramic capacitor between VCC and GND, placed as close as possible to the device pins. For systems with multiple EPROMs, a bulk 4.7 µF electrolytic capacitor should also be added near the array's power entry point. These values are mandated in the "System Considerations" section to suppress transient excursions during CE transitions.
How is the Product Identification Code read from the AT27C256R-12PI?
The Product Identification Code is read by setting A9 to 12.0 V ±0.5 V (VID), holding A1–A14 low, and toggling A0: low selects the Manufacturer ID byte (0x1E), high selects the Device Code byte (0x8C). Both bytes appear on O7–O0 during a standard read cycle with CE and OE asserted. This feature is used by industry-standard programmers to auto-detect device type and apply correct algorithms.
AT27C256R-12PI 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:
- EPROM
- Technology:
- EPROM - OTP
- Memory Size:
- 256Kbit
- Memory Organization:
- 32K x 8
- Memory Interface:
- Parallel
- Clock Frequency:
- -
- Write Cycle Time - Word, Page:
- -
- Access Time:
- 120 ns
- Voltage - Supply:
- 4.5V ~ 5.5V
- Operating Temperature:
- -40°C ~ 85°C (TC)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 28-PDIP
AT27C256R-12PI FAQ
1.How can I place an order for AT27C256R-12PI through Aetrix?
Please submit a Request for Quotation (RFQ) for AT27C256R-12PI 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 AT27C256R-12PI reliable?
The price and inventory of AT27C256R-12PI are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AT27C256R-12PI is usually 5 days.
3.What payment methods are accepted for AT27C256R-12PI?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AT27C256R-12PI transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AT27C256R-12PI?
AT27C256R-12PI orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AT27C256R-12PI 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 AT27C256R-12PI?
For technical support, including AT27C256R-12PI datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AT27C256R-12PI requirements.
6.How does Aetrix verify that AT27C256R-12PI is sourced from the original manufacturer or authorized distributors?
All AT27C256R-12PI 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 AT27C256R-12PI meets industry standards.
7.What is the process for return or replacement of AT27C256R-12PI?
All AT27C256R-12PI units undergo pre-shipment inspection (PSI). If there is an issue with AT27C256R-12PI, 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 AT27C256R-12PI part is unused and in its original packaging.
Return procedure for AT27C256R-12PI:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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