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Microchip Technology AT27C256R-45PI
- Part No.:
- AT27C256R-45PI
- Manufacturer:
- Microchip Technology
- Category:
- Memory
- Package:
- 28-DIP (0.600", 15.24mm)
- Datasheet:
-
AT27C256R-45PI.pdf
- Description:
- IC EPROM 256KBIT PARALLEL 28DIP
- Quantity:
- Payment:
- Shipping:
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Product details
Overview
AT27C256R-45PI from Atmel is a 256K-bit (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 compatibility, and rapid programming at 100 µs/byte - enabling firmware storage in microprocessor systems without wait states.
For engineers reviewing the AT27C256R-45PI datasheet, AT27C256R-45PI pinout, AT27C256R-45PI application, or AT27C256R-45PI equivalent, key selection criteria include verified 45 ns tACC timing, PDIP-28 package compatibility, VPP = 12.0 V programming voltage, standby current ≤100 µA, and integrated product identification code for automated programming equipment.
Technical Context
The AT27C256R-45PI implements a standard OTP EPROM architecture with address decoding for A0–A14, 8-bit bidirectional data outputs (O0–O7), and two active-low control lines (CE, OE) supporting bus contention avoidance. Its Rapid™ Programming Algorithm uses 100 µs CE pulses at VPP = 12.0 V and VCC = 6.5 V for byte-level programming and verification loops.
It supports three operating modes: Read (CE=OE=VIL), Output Disable (CE=VIL, OE=VIH), and Standby (CE=VIH); programming requires VPP = 12.0 V applied simultaneously with or after VCC. The device includes an integrated product ID code accessible via A9=VH and A0 toggling, returning Manufacturer ID (0x1E) and Device Code (0x8C).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory Size | 256 Kbit (32K × 8) - stores full firmware images for 8-bit microcontrollers without external memory controllers. |
| Read Access Time | 45 ns max - eliminates WAIT states on 5 MHz Z80, 8086, and 68000-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 - enables low-power retention in battery-backed embedded controllers. |
| Programming Voltage | VPP = 12.0 V ±0.5 V - requires dedicated programming supply; not used during normal read operation. |
| Operating Temperature | –40°C to +85°C - qualified for industrial automation, motor control, and instrumentation applications. |
| ESD Protection | 2,000 V HBM - ensures robustness during handling and PCB assembly in non-EPA environments. |
Pinout & Package
AT27C256R-45PI is supplied in a 28-lead, 0.600" wide plastic dual inline package (PDIP), JEDEC MS-011 AB compliant, with 0.100" lead pitch and through-hole mounting.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| A0–A14 | Address Inputs | 15-bit address bus interface; selects one of 32,768 bytes; TTL/CMOS compatible thresholds. |
| O0–O7 | Data Outputs | 8-bit unidirectional data bus; VOH ≥2.4 V at –400 µA, VOL ≤0.4 V at 2.1 mA - drives standard logic loads. |
| CE | Chip Enable | Active-low global enable; controls power state transition between Active (≤20 mA) and Standby (≤100 µA). |
| OE | Output Enable | Active-low output gate; enables high-impedance tri-state when deasserted - prevents bus contention. |
| VPP | Programming Supply | 12.0 V input for programming only; must be applied simultaneously with or after VCC per datasheet safety requirement. |
| VCC | Power Supply | +5 V main supply; powers internal logic and outputs; requires 0.1 µF ceramic decoupling capacitor adjacent to pin. |
| GND | Ground Reference | Signal and power return path; must be connected before VCC/VPP during power-up sequencing. |
| NC | No Connect | Pins 1 and 17 in PLCC variant are unconnected; PDIP-28 has no NC pins - all 28 pins assigned. |
Key Features
| Feature | Design Value |
|---|---|
| Rapid™ Programming | 100 µs/byte typical - reduces firmware update cycle time by >5× vs. legacy EPROMs; includes automatic verify/reprogram loop. |
| Integrated Product ID | Manufacturer ID 0x1E + Device Code 0x8C - enables auto-detection and algorithm selection in universal programmers (e.g., BP Microsystems, Xeltek). |
| Two-Line Control Logic | Separate CE and OE inputs - allows flexible memory mapping and avoids bus conflicts in multi-peripheral systems. |
| High-Reliability Process | 200 mA latchup immunity + 2,000 V ESD - meets industrial system robustness requirements without external protection circuitry. |
| JEDEC Standard Packages | PDIP-28 pinout matches industry-standard 27C256 footprint - enables drop-in replacement for legacy designs using 27C256B/C variants. |
Applications
| Industrial PLC Firmware Storage | Legacy 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: Non-volatile boot memory mapped to CPU address space; accessed at 5 MHz with zero wait states due to 45 ns tACC. Use Value: Eliminates reliance on slow serial EEPROM or external flash, reducing boot time and simplifying BOM with single-chip firmware storage. | Use Scenario: Providing fixed startup code and hardware initialization routines for Z80 or 8085-based test equipment and data loggers. IC Role / Device Role / Timing Role: Read-only instruction memory executing directly from address bus; CE/OE timing fully compatible with 8085 bus cycle timing. Use Value: Guarantees deterministic execution timing and eliminates software overhead from memory-mapped flash wear leveling or erase cycles. |
| Automotive Engine Control Calibration Data | Medical Device Safety-Critical Parameter Tables |
Use Scenario: Holding fuel injection timing maps and sensor calibration coefficients in engine control units operating across –40°C to +85°C. IC Role / Device Role / Timing Role: OTP storage for immutable calibration data; programmed once during final test, then read-only during vehicle operation. Use Value: Prevents accidental corruption or field updates - critical for ISO 26262 ASIL-B functional safety compliance where runtime write access is prohibited. | Use Scenario: Storing FDA-approved dose calculation coefficients and alarm thresholds in infusion pumps and diagnostic analyzers. IC Role / Device Role / Timing Role: Tamper-proof parameter repository; accessed during power-on self-test and real-time monitoring routines. Use Value: Meets IEC 62304 Class C software requirements by ensuring parameters cannot be altered post-manufacture without physical reprogramming. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar OTP EPROM applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AT27C256B-45PI | Same 256K × 8 OTP EPROM, but older revision with 55 ns tACC and higher standby current (200 µA). | Lacks Rapid™ programming algorithm; slower 200 µs/byte programming; no integrated ID code. | Select only if legacy board layout requires identical timing margins or if programming equipment lacks ID-code support. |
| MX27C256-45PC | Pin-compatible 256K × 8 OTP EPROM; same 45 ns tACC, but rated only for commercial temp (0°C to 70°C) and lacks VPP=12 V programming specification. | No automotive/industrial qualification; no product ID code; lower ESD rating (1,500 V). | Acceptable for cost-sensitive consumer electronics where extended temperature and programming reliability are not required. |
Compared with AT27C256B-45PI and MX27C256-45PC, the AT27C256R-45PI delivers faster programming, lower standby power, guaranteed industrial temperature operation, and automated programmer compatibility via its integrated ID code - making it the preferred choice for new industrial and automotive designs requiring long-term firmware integrity.
Availability
AT27C256R-45PI is available at Aetrix Electronics and suitable for industrial PLCs, legacy microcontroller boot systems, automotive engine control units, medical device calibration storage, and test equipment firmware applications requiring stable component supply over extended production lifecycles.
Supply support for AT27C256R-45PI 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 fabless semiconductor company specializing in microcontrollers, non-volatile memory, and secure authentication ICs.
The AT27C256R belongs to Atmel's OTP EPROM product line, designed specifically for reliable, low-cost, one-time firmware storage in industrial, automotive, and medical systems where data immutability and long-term bit retention are mandatory.
FAQ
What is the maximum allowed VPP voltage for programming the AT27C256R-45PI?
The AT27C256R-45PI requires VPP = 12.0 V ±0.5 V during programming, as specified in the DC Programming Characteristics table. Exceeding 12.5 V risks permanent damage, while voltages below 11.5 V may cause incomplete programming. The AT27C256R-45PI datasheet explicitly prohibits connecting VPP directly to VCC during programming - a separate regulated 12 V supply is mandatory.
Can the AT27C256R-45PI operate with a 3.3 V supply?
No, the AT27C256R-45PI is strictly a 5 V ±10% device. Its input thresholds (VIL ≤0.8 V, VIH ≥2.0 V), output drive strength (VOH ≥2.4 V at –400 µA), and internal logic are designed for 5 V TTL/CMOS compatibility. Using 3.3 V will result in undefined behavior, failed reads, and potential bus contention - the AT27C256R-45PI does not support mixed-voltage interfacing.
Does the AT27C256R-45PI support in-system programming?
No, the AT27C256R-45PI requires external programming equipment applying 12 V to VPP and precise timing waveforms (e.g., 100 µs CE pulses). It lacks serial interfaces, JTAG, or ISP circuitry. Programming must occur off-board using certified EPROM programmers such as Data I/O PS-3000 or BP Microsystems SuperPro 500S - the AT27C256R-45PI is not field-programmable in situ.
What decoupling capacitors are required for stable operation of the AT27C256R-45PI?
The AT27C256R-45PI requires a 0.1 µF ceramic capacitor placed between VCC and GND, mounted as close as possible to the device pins to suppress high-frequency transients. For systems with multiple AT27C256R-45PI devices or large EPROM arrays, a 4.7 µF bulk electrolytic capacitor must also be added near the power entry point - both are mandatory per the "System Considerations" section of the AT27C256R-45PI datasheet.
Is the AT27C256R-45PI RoHS compliant?
Yes, the AT27C256R-45PI is RoHS compliant per Atmel's product change notification PCN#03-110101. It contains no lead, mercury, cadmium, hexavalent chromium, PBB, or PBDE above threshold limits. The PDIP package uses matte tin lead finish, and the device meets JEDEC J-STD-609 Category 1 marking requirements - full compliance documentation is available upon request for the AT27C256R-45PI.
AT27C256R-45PI 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:
- 45 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-45PI FAQ
1.How can I place an order for AT27C256R-45PI through Aetrix?
Please submit a Request for Quotation (RFQ) for AT27C256R-45PI 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-45PI reliable?
The price and inventory of AT27C256R-45PI are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AT27C256R-45PI is usually 5 days.
3.What payment methods are accepted for AT27C256R-45PI?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AT27C256R-45PI transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AT27C256R-45PI?
AT27C256R-45PI orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AT27C256R-45PI 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-45PI?
For technical support, including AT27C256R-45PI datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AT27C256R-45PI requirements.
6.How does Aetrix verify that AT27C256R-45PI is sourced from the original manufacturer or authorized distributors?
All AT27C256R-45PI 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-45PI meets industry standards.
7.What is the process for return or replacement of AT27C256R-45PI?
All AT27C256R-45PI units undergo pre-shipment inspection (PSI). If there is an issue with AT27C256R-45PI, 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-45PI part is unused and in its original packaging.
Return procedure for AT27C256R-45PI:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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