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Microchip Technology AT27C256R-12RI
- Part No.:
- AT27C256R-12RI
- Manufacturer:
- Microchip Technology
- Category:
- Memory
- Package:
- 28-SOIC (0.342", 8.69mm Width)
- Datasheet:
-
AT27C256R-12RI.pdf
- Description:
- IC EPROM 256KBIT PARALLEL 28SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:1,746
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Product details
Overview
AT27C256R-12RI from Microchip Technology (formerly Atmel) is a 32K × 8-bit one-time programmable EPROM used for firmware storage in microprocessor systems, featuring 45 ns read access time, 5V ±10% supply operation, and industrial temperature range (–40°C to +85°C). It supports CE/OE dual-line control, delivers 20 mA active current at 5 MHz, and integrates Rapid™ programming with 100 µs/byte typical write speed.
For engineers reviewing the AT27C256R-12RI datasheet, AT27C256R-12RI pinout, AT27C256R-12RI application, or AT27C256R-12RI equivalent, key selection criteria include OTP reliability, JEDEC-standard SOIC-28 packaging, VPP-programming voltage handling (12.0 V ±0.5 V), and compatibility with legacy 5V bus architectures requiring no WAIT states.
Technical Context
The AT27C256R-12RI implements a CMOS-based OTP EPROM architecture with address decoding for A0–A14 (15-bit), eight bidirectional data outputs (O0–O7), and two-level chip enable (CE) and output enable (OE) control. Its Rapid™ programming algorithm uses precise 100 µs CE pulses at VPP = 13.0 V to achieve verified byte programming without iterative rewrites under standard conditions.
It features integrated product identification logic (A9 = 12.0 V, A0 toggled) to auto-detect manufacturer (0x1E) and device code (0x8C), enabling automatic algorithm selection in industry-standard programmers. The device operates in Read, Standby, Rapid Program, PGM Verify, and Product ID modes-all defined by specific CE/OE/VPP voltage combinations and timing windows.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory Size | 32K × 8 bits (262,144-bit OTP EPROM) |
| Read Access Time | 45 ns - eliminates WAIT states in 5 MHz+ microprocessor buses |
| Supply Voltage | 5 V ±10% - compatible with standard TTL/CMOS logic rails |
| Active Current | 20 mA max at 5 MHz - enables low-power embedded system integration |
| Standby Current | 100 µA max - supports battery-backed or low-quiescent designs |
| VPP Programming Voltage | 12.0 V ±0.5 V - required for reliable byte programming; not used in read mode |
| Operating Temperature | –40°C to +85°C - qualified for industrial-grade environmental resilience |
| ESD Protection | 2,000 V HBM - ensures robustness during handling and board assembly |
Pinout & Package
AT27C256R-12RI is packaged in a 28-lead SOIC (Small Outline Integrated Circuit), 0.330" wide, JEDEC MS-012 compliant, with gull-wing leads and surface-mount footprint.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| A0–A14 | Address Inputs | 15-bit address bus interface; selects one of 32,768 memory locations |
| O0–O7 | Data Outputs | 8-bit bidirectional data bus; driven only when CE = OE = low |
| CE | Chip Enable | Primary device select; high-Z output when high; enables internal logic when low |
| OE | Output Enable | Secondary output gate; controls data bus drive timing independent of CE |
| VPP | Programming Voltage | 12 V input required only during programming; must be applied after VCC and removed before VCC |
| VCC | Power Supply | +5 V main supply; powers all logic and output drivers in read mode |
| GND | Ground Reference | Signal and power return path; requires local 0.1 µF ceramic decoupling |
| NC | No Connect | Unbonded pin; must remain unconnected per design (no internal connection) |
Key Features
| Feature | Design Value |
|---|---|
| Rapid™ Programming Algorithm | 100 µs/byte typical - reduces firmware burn time and improves production throughput |
| Integrated Product ID Code | Manufacturer ID (0x1E) and Device Code (0x8C) - enables auto-configuration in universal programmers |
| Dual-Line Control (CE/OE) | Independent chip and output gating - prevents bus contention in multi-device systems |
| JEDEC-Standard Packaging | SOIC-28 footprint - ensures drop-in compatibility with existing PCB layouts and pick-and-place tooling |
| High-Reliability CMOS Process | 200 mA latchup immunity and 2 kV ESD - meets industrial system robustness requirements |
Applications
| Industrial PLC Firmware Storage | Legacy Embedded System Boot ROM |
|---|---|
Use Scenario: Storing fixed ladder logic and I/O configuration in programmable logic controllers deployed in factory automation environments. IC Role / Device Role / Timing Role: Non-volatile boot memory providing deterministic startup sequence and runtime firmware access. Use Value: 45 ns access time ensures real-time response without CPU wait-state insertion, improving scan cycle efficiency. | Use Scenario: Holding BIOS or bootloader code in 1990s–2000s-era embedded controllers where flash replacement was cost-prohibitive. IC Role / Device Role / Timing Role: Primary read-only instruction memory mapped into microprocessor address space. Use Value: OTP reliability eliminates risk of accidental overwrite during field operation-critical for unattended deployments. |
| Military Communications Equipment | Automotive Diagnostic Module Memory |
Use Scenario: Securing cryptographic keys and protocol stacks in ruggedized HF/VHF radio transceivers operating across –40°C to +85°C. IC Role / Device Role / Timing Role: Tamper-resistant firmware repository with no volatile write capability post-deployment. Use Value: Industrial temp grade and 2 kV ESD rating ensure uninterrupted operation in EMI-heavy vehicle and field environments. | Use Scenario: Storing OBD-II diagnostic routines and calibration tables in engine control modules requiring long-term data integrity. IC Role / Device Role / Timing Role: Read-only execution memory accessed directly by 8/16-bit MCUs during power-up and fault analysis. Use Value: 100 µA standby current minimizes parasitic drain on vehicle battery during extended parking periods. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar OTP EPROM applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AM27C256B-12DC | Same 32K×8 OTP EPROM, but AMD-manufactured; 120 ns access time (slower), 5V-only VPP (no 12V requirement) | Lower programming voltage simplifies programmer design but sacrifices speed and compatibility with Atmel's Rapid™ algorithm | Select if VPP circuitry is constrained and 120 ns read latency is acceptable in target system |
| MX27C256-12PC | Macronix OTP EPROM; identical 45 ns access and 12V VPP, but lacks integrated product ID code and has higher standby current (200 µA) | Requires manual algorithm selection in programmers; less suitable for automated high-volume programming lines | Choose when cost sensitivity outweighs ID-code automation benefits and 100 µA vs. 200 µA standby is non-critical |
Compared with AM27C256B-12DC and MX27C256-12PC, the AT27C256R-12RI uniquely combines 45 ns speed, 12V-programmable reliability, and auto-identifiable silicon-making it optimal for industrial systems demanding both performance and programming line efficiency.
Availability
AT27C256R-12RI is available at Aetrix Electronics and suitable for industrial PLCs, legacy embedded boot systems, military comms hardware, automotive diagnostic modules, and aerospace avionics requiring stable component supply across extended lifecycles.
Supply support for AT27C256R-12RI 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 technical and supply chain continuity for legacy Atmel memory products including the AT27C256R series.
The AT27C256R product line was designed for cost-sensitive, high-reliability embedded systems requiring immutable firmware storage-targeting industrial control, communications infrastructure, and automotive subsystems where flash wear-out or accidental reprogramming posed unacceptable risk.
FAQ
What is the correct VPP voltage for programming the AT27C256R-12RI?
The AT27C256R-12RI requires a VPP voltage of 12.0 V ±0.5 V during programming. This voltage must be applied after VCC and removed before VCC to prevent latchup or damage. The device will not program reliably outside this range, and exceeding 12.5 V risks permanent degradation of the oxide layer. Always verify VPP stability with an oscilloscope during pulse application.
Does the AT27C256R-12RI support in-system programming?
No, the AT27C256R-12RI does not support in-system programming. It requires dedicated EPROM programmers capable of delivering 12 V to the VPP pin and executing the Rapid™ algorithm-including address sequencing, 100 µs CE pulses, and verification loops. The device lacks serial interfaces or command protocols for embedded controller-driven writes.
Can the AT27C256R-12RI be used as a direct replacement for the AT27C256B-12RI?
Yes, the AT27C256R-12RI is a functional and pin-compatible replacement for the AT27C256B-12RI. Both share identical pinout, timing specifications (45 ns tACC), VPP requirements, and industrial temperature rating. The "R" suffix denotes enhanced reliability screening and updated process, with no electrical or mechanical incompatibility introduced.
What decoupling capacitors are required for stable operation of the AT27C256R-12RI?
The AT27C256R-12RI requires a 0.1 µF ceramic capacitor placed between VCC and GND, mounted as close as possible to the device pins. For systems with multiple EPROMs, a 4.7 µF bulk electrolytic capacitor should also be added near the power entry point. These values are specified in the Atmel datasheet to suppress transient excursions during CE transitions and ensure data sheet compliance.
How is the manufacturer and device identification code read from the AT27C256R-12RI?
The AT27C256R-12RI identification code is read by setting A9 to 12.0 V (VID = 11.5–12.5 V), holding A1–A14 low, and toggling A0: low reads the Manufacturer ID (0x1E), high reads the Device Code (0x8C). Outputs O7–O0 reflect the 8-bit code while CE and OE are both low. This mode is electrically distinct from normal read operation and requires precise VPP-level control.
AT27C256R-12RI Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Microchip Technology
- Series:
- -
- Package/Case:
- 28-SOIC (0.342", 8.69mm Width)
- 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:
- Surface Mount
- Supplier Device Package:
- 28-SOIC
AT27C256R-12RI FAQ
1.How can I place an order for AT27C256R-12RI through Aetrix?
Please submit a Request for Quotation (RFQ) for AT27C256R-12RI 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-12RI reliable?
The price and inventory of AT27C256R-12RI are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AT27C256R-12RI is usually 5 days.
3.What payment methods are accepted for AT27C256R-12RI?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AT27C256R-12RI transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AT27C256R-12RI?
AT27C256R-12RI orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AT27C256R-12RI 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-12RI?
For technical support, including AT27C256R-12RI datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AT27C256R-12RI requirements.
6.How does Aetrix verify that AT27C256R-12RI is sourced from the original manufacturer or authorized distributors?
All AT27C256R-12RI 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-12RI meets industry standards.
7.What is the process for return or replacement of AT27C256R-12RI?
All AT27C256R-12RI units undergo pre-shipment inspection (PSI). If there is an issue with AT27C256R-12RI, 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-12RI part is unused and in its original packaging.
Return procedure for AT27C256R-12RI:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
AT27C256R-12RI Tags
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M24C02-WMN6TP
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AT24C02C-XHM-T
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