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Microchip Technology AT27C256R-55RC
- Part No.:
- AT27C256R-55RC
- Manufacturer:
- Microchip Technology
- Category:
- Memory
- Package:
- 28-SOIC (0.342", 8.69mm Width)
- Datasheet:
-
AT27C256R-55RC.pdf
- Description:
- IC EPROM 256KBIT PARALLEL 28SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:1,564
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Product details
Overview
AT27C256R-55RC from Microchip Technology (formerly Atmel) is a 32K × 8-bit one-time programmable EPROM used for nonvolatile firmware storage in microprocessor systems. It delivers 45 ns read access time, operates from a single 5V ±10% supply, and supports commercial temperature range (0°C to 70°C) in 28-lead SOIC package. It enables fast, latchup-immune code execution without wait states.
For engineers reviewing the AT27C256R-55RC datasheet, AT27C256R-55RC pinout, AT27C256R-55RC application, or AT27C256R-55RC equivalent, key selection factors include verified 45 ns tACC, CMOS/TTL I/O compatibility, Rapid™ programming at 100 µs/byte, VPP = 12.0 V programming voltage, and JEDEC-standard SOIC packaging with 28-pin gull-wing leadform.
Technical Context
The AT27C256R-55RC implements a standard OTP EPROM architecture with dual-line control (CE and OE), enabling bus contention avoidance in shared-data-bus systems. Its address space spans A0–A14 (15 bits), supporting full 32K-byte decoding, and includes dedicated VPP pin for 12.0 V ±0.5 V programming voltage.
It uses scaled CMOS technology to achieve 100 µA max standby current and 20 mA max active current at 5 MHz, with integrated product identification code accessible via A9/VH and A0 toggling. The device supports rapid program-verify cycles and optional PGM verify modes per JEDEC EPROM standards.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory Size | 256 Kbit (32K × 8) - supports full 32 KB firmware image storage with byte-level random access |
| Read Access Time | 45 ns - eliminates WAIT states on 5 MHz+ microprocessors such as 80C86, Z80, and 68000 derivatives |
| Supply Voltage | 5 V ±10% - compatible with standard TTL/CMOS logic rails; no auxiliary voltage required for read operation |
| Standby Current | 100 µA max - enables low-power retention in battery-backed or intermittent-operation embedded systems |
| Programming Voltage | VPP = 12.0 V ±0.5 V - requires external high-voltage source during programming; not used in read mode |
| ESD Protection | 2,000 V HBM - ensures robust handling during board assembly and field service without special ESD controls |
| Latchup Immunity | 200 mA - prevents destructive latchup under transient overvoltage or ground bounce conditions |
Pinout & Package
AT27C256R-55RC is packaged in a 28-lead, 0.330" wide plastic gull-wing small outline (SOIC), JEDEC MS-012 compliant, with 1.27 mm pitch and surface-mount footprint.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| A0–A14 | Address Inputs | 15-bit address bus interface; fully decoded to select one of 32,768 bytes |
| O0–O7 | Data Outputs | 8-bit bidirectional data bus outputs; CMOS/TTL-compatible with VOH ≥ 2.4 V and VOL ≤ 0.4 V |
| CE | Chip Enable | Active-low chip select; must be asserted before OE to enable output drivers and prevent bus contention |
| OE | Output Enable | Active-low output gate; allows shared-bus operation by disabling outputs while CE remains active |
| VPP | Programming Voltage | 12.0 V input required only during programming; must be applied simultaneously with or after VCC |
| GND | Ground Reference | Signal and power return; requires local 0.1 µF ceramic decoupling per device |
| VCC | Power Supply | +5 V ±10% main supply; powers all internal logic and output buffers during read and standby |
Key Features
| Feature | Design Value |
|---|---|
| Rapid™ Programming Algorithm | 100 µs/byte typical - reduces firmware update time by >5× vs. legacy EPROMs; includes auto-retry up to 10 pulses per byte |
| Integrated Product ID Code | Manufacturer ID = 0x1E, Device ID = 0x8C - enables automatic algorithm selection in industry-standard programmers (e.g., BP Microsystems, Xeltek) |
| Two-Line Control Architecture | Separate CE and OE inputs - permits flexible memory mapping and eliminates need for external bus transceivers in multi-peripheral systems |
| JEDEC-Standard Packaging | 28-lead SOIC (28R) - ensures drop-in compatibility with existing PCB footprints designed for 27C256, 27C512, or AM27C256 equivalents |
| Temperature Range Support | Commercial (0°C to 70°C) - validated for use in office equipment, industrial HMIs, and consumer electronics where ambient thermal stress is controlled |
Applications
| Industrial PLC Firmware Storage | Legacy Computer BIOS Retention |
|---|---|
Use Scenario: Storing ladder logic and configuration tables in modular programmable logic controllers deployed in factory automation cabinets. IC Role / Device Role / Timing Role: Nonvolatile firmware ROM providing deterministic 45 ns instruction fetch timing to ensure scan-cycle predictability. Use Value: Eliminates reliance on battery-backed SRAM or slow serial EEPROM, reducing BOM count and improving mean time between failures (MTBF). | Use Scenario: Holding boot firmware and hardware initialization routines in retro-computing restoration projects using original IBM PC/AT or compatible motherboards. IC Role / Device Role / Timing Role: Pin-identical replacement for obsolete 27C256 EPROMs, delivering identical 5V-only read operation and SOIC footprint. Use Value: Restores full system functionality without PCB modification, leveraging verified 20 mA active drive strength to meet legacy bus loading requirements. |
| Medical Device Bootloader | Test Equipment Calibration Data |
Use Scenario: Securing immutable bootloader code in Class II medical instruments requiring FDA 21 CFR Part 11 compliance and revision-controlled firmware. IC Role / Device Role / Timing Role: One-time programmable ROM ensuring firmware integrity; no runtime write capability prevents accidental corruption. Use Value: Meets IEC 62304 software safety requirements for SOUP (Software of Unknown Provenance) by eliminating field-updatable code paths. | Use Scenario: Storing factory-calibrated ADC offset/gain coefficients and sensor linearization tables in benchtop multimeters and oscilloscopes. IC Role / Device Role / Timing Role: Read-only calibration memory accessed once at power-on; low 100 µA standby current preserves battery life in portable units. Use Value: Enables traceable, unalterable calibration records without requiring secure microcontroller flash or external EEPROM encryption. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar OTP EPROM applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AT27C256R-45RC | 45 ns access time (vs. 55 ns); otherwise identical pinout, voltage, and programming specs | Suitable for higher-speed 8-MHz Z80 or 10-MHz 8088 systems where tACC margin is critical | Select when system timing budget requires <50 ns read latency; same SOIC package and programming flow |
| AM27C256B-55DC | Same 55 ns speed grade and 32K×8 organization; manufactured by AMD (now discontinued, available via authorized legacy distributors) | Validated in legacy telecom line cards and military avionics where AMD qualification history is mandated | Choose only if legacy design documentation explicitly references AM27C256B; not recommended for new designs due to obsolescence risk |
Compared with AT27C256R-45RC, the AT27C256R-55RC trades 10 ns read latency for broader availability and lower cost in commercial-grade SOIC; versus AM27C256B-55DC, it offers active manufacturing support, full Microchip documentation, and guaranteed long-term supply continuity.
Availability
AT27C256R-55RC is available at Aetrix Electronics and suitable for industrial PLC firmware storage, legacy computer BIOS retention, and medical device bootloader applications requiring stable component supply across multi-year production cycles.
Supply support for AT27C256R-55RC 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 is a global semiconductor company specializing in microcontrollers, analog devices, and nonvolatile memory solutions, with headquarters in Chandler, Arizona.
The AT27C256R belongs to Microchip's legacy OTP EPROM product line, designed specifically for reliable, low-cost firmware storage in cost-sensitive industrial, computing, and instrumentation applications where reprogrammability is unnecessary.
FAQ
What is the maximum operating frequency supported by AT27C256R-55RC?
The AT27C256R-55RC does not operate at a clock frequency-it is an asynchronous memory device. Its performance is defined by access time: tACC = 55 ns maximum, enabling reliable interfacing with microprocessors running up to approximately 12 MHz (assuming no wait states). System timing must satisfy tCE, tOE, and tDF specifications per the AC characteristics table in the official Microchip datasheet for AT27C256R-55RC.
Does AT27C256R-55RC require a programming voltage during normal read operation?
No, AT27C256R-55RC requires only a single +5 V ±10% supply for normal read and standby operation. The VPP pin (12.0 V ±0.5 V) is used exclusively during programming and must be disconnected or held at VCC during read mode. Applying VPP during read may damage the device or cause undefined behavior.
Can AT27C256R-55RC be used as a direct replacement for AT27C256R-55PC (PDIP package)?
Yes, AT27C256R-55RC is functionally and electrically identical to AT27C256R-55PC, differing only in package type: SOIC (28R) vs. PDIP (28P6). Pin functions and numbering are identical, but physical layout and soldering method differ. PCB redesign is required to accommodate the surface-mount SOIC footprint of AT27C256R-55RC versus through-hole PDIP mounting.
What is the purpose of the Integrated Product Identification Code in AT27C256R-55RC?
The Integrated Product Identification Code in AT27C256R-55RC provides two factory-programmed bytes: Manufacturer ID (0x1E) and Device ID (0x8C). Accessed via A9 = 12.0 V and A0 toggling, it allows automated programmers to validate device authenticity and auto-select correct programming algorithms and voltage profiles-ensuring reliable one-time programming of AT27C256R-55RC without manual configuration.
Is AT27C256R-55RC suitable for automotive applications?
No, AT27C256R-55RC is rated for commercial temperature range (0°C to 70°C) only. For automotive use, Microchip offers the AT27C256R-55RA variant (–40°C to +125°C), which shares identical electrical specs and pinout but undergoes extended temperature qualification and AEC-Q100 stress testing. Using AT27C256R-55RC in automotive environments risks parametric drift and premature failure outside its specified operating range.
AT27C256R-55RC 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:
- 55 ns
- Voltage - Supply:
- 4.5V ~ 5.5V
- Operating Temperature:
- 0°C ~ 70°C (TC)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 28-SOIC
AT27C256R-55RC FAQ
1.How can I place an order for AT27C256R-55RC through Aetrix?
Please submit a Request for Quotation (RFQ) for AT27C256R-55RC 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-55RC reliable?
The price and inventory of AT27C256R-55RC are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AT27C256R-55RC is usually 5 days.
3.What payment methods are accepted for AT27C256R-55RC?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AT27C256R-55RC transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AT27C256R-55RC?
AT27C256R-55RC orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AT27C256R-55RC 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-55RC?
For technical support, including AT27C256R-55RC datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AT27C256R-55RC requirements.
6.How does Aetrix verify that AT27C256R-55RC is sourced from the original manufacturer or authorized distributors?
All AT27C256R-55RC 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-55RC meets industry standards.
7.What is the process for return or replacement of AT27C256R-55RC?
All AT27C256R-55RC units undergo pre-shipment inspection (PSI). If there is an issue with AT27C256R-55RC, 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-55RC part is unused and in its original packaging.
Return procedure for AT27C256R-55RC:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
AT27C256R-55RC Tags
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M24C02-WMN6TP
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AT24C02C-XHM-T
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AT21CS01-STUM10-T
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AT24CS02-SSHM-T
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