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Microchip Technology AT27C256R-45RI
- Part No.:
- AT27C256R-45RI
- Manufacturer:
- Microchip Technology
- Category:
- Memory
- Package:
- 28-SOIC (0.342", 8.69mm Width)
- Datasheet:
-
AT27C256R-45RI.pdf
- Description:
- IC EPROM 256KBIT PARALLEL 28SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:1,230
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Product details
Overview
AT27C256R-45RI from Microchip Technology (formerly Atmel) is a 256 Kbit (32K × 8) one-time programmable EPROM with 45 ns read access time, 5V ±10% supply, and industrial temperature range (–40°C to +85°C). It features dual-line control (CE/OE), CMOS/TTL-compatible I/O, and Rapid™ programming at 100 µs/byte - used for firmware storage in microcontroller-based embedded systems requiring nonvolatile, pin-compatible legacy memory replacement.
For engineers reviewing the AT27C256R-45RI datasheet, AT27C256R-45RI pinout, AT27C256R-45RI application, or AT27C256R-45RI equivalent, key selection criteria include verified 45 ns tACC timing, VPP = 12.0 V programming voltage, 100 µA max standby current, and JEDEC-standard 28-lead SOIC (28R) package compatibility with legacy board layouts.
Technical Context
The AT27C256R-45RI implements a standard OTP EPROM architecture with address decoding for A0–A14 (15-bit), 8-bit bidirectional data bus (O0–O7), and two active-low control lines: Chip Enable (CE) and Output Enable (OE). Its internal logic supports three primary modes - Read, Standby, and Rapid Programming - each defined by specific CE/OE/VPP voltage combinations.
It uses scaled CMOS process technology enabling 20 mA max active current at 5 MHz and 100 µA max standby current, while maintaining 2,000V ESD protection and 200 mA latchup immunity. The Integrated Product Identification Code (Manufacturer ID = 0x1E, Device ID = 0x8C) is accessed via A9 high-voltage (11.5–12.5 V) and A0 toggling, supporting automated programmer recognition.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory Size | 256 Kbit (32,768 × 8 bits) - supports full firmware image storage for 8-bit microcontrollers without external banking logic. |
| Read Access Time | 45 ns maximum - eliminates WAIT states on 5 MHz Z80, 8051, and 68K-based systems. |
| Supply Voltage | 5 V ±10% - compatible with standard TTL/CMOS logic rails; no auxiliary voltage required for read operation. |
| Standby Current | 100 µA maximum - enables low-power retention in battery-backed or energy-sensitive industrial controllers. |
| Programming Voltage | VPP = 12.0 V ±0.5 V - requires dedicated programming hardware; not used during normal read operation. |
| Operating Temperature | –40°C to +85°C - qualified for industrial-grade embedded applications including PLCs and motor drives. |
| ESD Protection | 2,000 V HBM - meets IEC 61000-4-2 Level 2 for robustness in manufacturing and field environments. |
Pinout & Package
AT27C256R-45RI is supplied in a 28-lead SOIC (28R) package per JEDEC MS-012, 0.330" wide body, with 1.27 mm pitch. Pin 1 marked by index notch; pin 1 is A12 (not NC).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| A0–A14 | Address Inputs | 15-bit address bus accepting 0x0000–0x7FFF; decoded internally to select one of 32,768 bytes. |
| O0–O7 | Data Outputs | 8-bit tristate output bus; driven only when CE = OE = low; high-impedance otherwise. |
| CE | Chip Enable | Active-low global enable; places device in Standby (high-Z) when high, enabling bus sharing. |
| OE | Output Enable | Active-low output gate; allows multiple devices on same data bus with staggered OE timing. |
| VPP | Programming Voltage | 12.0 V input required only during programming; must be applied after VCC and removed before VCC. |
| VCC | Power Supply | +5 V supply; powers all internal logic and output drivers during read and programming modes. |
| GND | Ground Reference | Return path for VCC and VPP; requires local 0.1 µF ceramic decoupling per device. |
Key Features
| Feature | Design Value |
|---|---|
| Rapid™ Programming Algorithm | 100 µs/byte typical - reduces firmware update time by >5× vs. conventional EPROM algorithms; includes auto-verify/reprogram loop. |
| Integrated Product ID Code | Manufacturer ID = 0x1E, Device ID = 0x8C - enables automatic algorithm selection in commercial programmers (e.g., Data I/O PS-200). |
| Dual-Line Control (CE/OE) | Independent chip and output gating - prevents bus contention in multi-device memory maps; supports partial-address decoding. |
| High-Reliability CMOS Process | 200 mA latchup immunity - ensures immunity to transient overcurrent events in noisy industrial power environments. |
| JEDEC-Standard Packaging | 28-lead SOIC (28R) footprint - direct drop-in replacement for obsolete 27C256 variants in existing PCBs. |
Applications
| Industrial PLC Firmware Storage | Legacy 8-bit Microcontroller Boot ROM |
|---|---|
Use Scenario: Storing ladder logic interpreter and I/O configuration tables in DIN-rail mounted programmable logic controllers. IC Role / Device Role / Timing Role: Nonvolatile boot memory mapped to CPU address space; accessed at power-on reset with ≤45 ns latency. Use Value: Eliminates reliance on slow serial EEPROM or external flash; ensures deterministic boot timing under -40°C cold-start conditions. | Use Scenario: Holding fixed initialization code and interrupt vectors for Z80 or 8051-based instrumentation front-ends. IC Role / Device Role / Timing Role: Primary read-only program memory; directly interfaced to CPU data/address buses without glue logic. Use Value: Guarantees sub-50 ns instruction fetch latency, enabling real-time response in 100 kHz sampling systems. |
| Automated Test Equipment (ATE) Pattern Memory | Avionics Maintenance Diagnostic Module |
Use Scenario: Storing digital test pattern sequences for semiconductor wafer probers and board-level functional testers. IC Role / Device Role / Timing Role: Static pattern store accessed sequentially by pattern generator state machine; CE toggled per vector. Use Value: Provides deterministic 45 ns access across full temperature range, critical for <100 ns timing margin compliance in high-speed ATE. | Use Scenario: Hosting diagnostic firmware and lookup tables in portable Line Replaceable Units (LRUs) for aircraft engine monitoring. IC Role / Device Role / Timing Role: Radiation-tolerant (non-flash) firmware store; accessed during pre-flight self-test at ambient –40°C to +70°C. Use Value: Delivers guaranteed data retention >20 years without refresh, meeting DO-160E Section 22 environmental stress requirements. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar OTP EPROM applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AT27C256B-45RI | Same pinout and timing; revised process with improved VPP tolerance (12.0 V ±0.3 V vs. ±0.5 V) and lower ICC active current (18 mA max). | Identical industrial temperature range and SOIC packaging; validated for new designs where tighter VPP regulation is available. | Select AT27C256B-45RI for new designs requiring lower power or enhanced programming yield; not recommended for legacy boards using older programmer firmware. |
| MX27C256-45L | 45 ns access, 5V supply, but requires VPP = 21 V for programming; different pin 1 location (A0 vs. A12); no integrated ID code. | Compatible in read mode only; requires hardware redesign for programming interface and board layout due to pinout shift and higher VPP. | Choose MX27C256-45L only if sourcing constraints require Macronix supply chain; expect revalidation of programming flow and layout changes. |
Compared with AT27C256R-45RI, the AT27C256B-45RI offers tighter VPP spec and lower active current but identical footprint and timing, while MX27C256-45L demands VPP hardware redesign and lacks ID-code automation - making AT27C256R-45RI optimal for drop-in industrial replacement where legacy tooling and layout reuse are mandatory.
Availability
AT27C256R-45RI is available at Aetrix Electronics and suitable for industrial PLCs, legacy microcontroller boot systems, automated test equipment, and avionics diagnostic modules requiring stable component supply and long-term obsolescence management.
Supply support for AT27C256R-45RI 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 product support, datasheets, and legacy programming specifications for the AT27C256R family.
The AT27C256R series was designed as a pin- and function-compatible upgrade to industry-standard 27C256 EPROMs, targeting industrial control, test equipment, and aerospace maintenance systems needing reliable, nonvolatile firmware storage without flash wear-out concerns.
FAQ
What is the maximum operating temperature range for the AT27C256R-45RI?
The AT27C256R-45RI is rated for industrial temperature operation from –40°C to +85°C. This range is confirmed in the Ordering Information table on page 9 of the official datasheet, where the suffix "I" denotes industrial grade. It is not rated for automotive (–40°C to +125°C) or extended commercial ranges.
Does the AT27C256R-45RI require VPP during normal read operation?
No, the AT27C256R-45RI does not require VPP during normal read operation. VPP = 12.0 V is needed only during programming and verification cycles. In read mode, only VCC = 5 V ±10% is required, simplifying system power design and eliminating need for high-voltage generation circuitry.
Can the AT27C256R-45RI be used as a direct replacement for the original AT27C256 in existing PCBs?
Yes, the AT27C256R-45RI is a direct functional and pinout replacement for the AT27C256, retaining identical 28-lead SOIC (28R) packaging, address/data/control pin assignments, and 45 ns timing. The "R" revision adds Rapid™ programming and improved ESD/latchup specs without altering read-mode behavior or footprint.
What programming voltage and pulse width are required for the AT27C256R-45RI?
The AT27C256R-45RI requires VPP = 12.0 V ±0.5 V and a CE programming pulse width of 95–105 µs (typical 100 µs) per byte, as specified in the AC Programming Characteristics table on page 7 of the datasheet. A 0.1 µF capacitor between VPP and GND is mandatory to suppress transients during programming.
How is the Integrated Product Identification Code accessed on the AT27C256R-45RI?
The Integrated Product Identification Code on the AT27C256R-45RI is accessed by setting A9 to 11.5–12.5 V (VID), holding A1–A14 low, and toggling A0: low selects Manufacturer ID (0x1E), high selects Device ID (0x8C). This occurs during special read mode with CE = OE = VIL, as detailed on page 8 of the datasheet.
AT27C256R-45RI 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:
- 45 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-45RI FAQ
1.How can I place an order for AT27C256R-45RI through Aetrix?
Please submit a Request for Quotation (RFQ) for AT27C256R-45RI 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-45RI reliable?
The price and inventory of AT27C256R-45RI are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AT27C256R-45RI is usually 5 days.
3.What payment methods are accepted for AT27C256R-45RI?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AT27C256R-45RI transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AT27C256R-45RI?
AT27C256R-45RI orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AT27C256R-45RI 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-45RI?
For technical support, including AT27C256R-45RI datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AT27C256R-45RI requirements.
6.How does Aetrix verify that AT27C256R-45RI is sourced from the original manufacturer or authorized distributors?
All AT27C256R-45RI 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-45RI meets industry standards.
7.What is the process for return or replacement of AT27C256R-45RI?
All AT27C256R-45RI units undergo pre-shipment inspection (PSI). If there is an issue with AT27C256R-45RI, 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-45RI part is unused and in its original packaging.
Return procedure for AT27C256R-45RI:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
AT27C256R-45RI Tags
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