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Microchip Technology AT27C256R-55PI
- Part No.:
- AT27C256R-55PI
- Manufacturer:
- Microchip Technology
- Category:
- Memory
- Package:
- 28-DIP (0.600", 15.24mm)
- Datasheet:
-
AT27C256R-55PI.pdf
- Description:
- IC EPROM 256KBIT PARALLEL 28DIP
- Quantity:
- Payment:
- Shipping:
Inventory:1,530
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Product details
Overview
AT27C256R-55PI from Microchip Technology (formerly Atmel) is a 256 Kbit (32K × 8) one-time programmable EPROM with 55 ns maximum read access time, 5V ±10% supply operation, 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 ROM replacement.
For engineers reviewing the AT27C256R-55PI datasheet, AT27C256R-55PI pinout, AT27C256R-55PI application, or AT27C256R-55PI equivalent, key selection criteria include verified 55 ns tACC timing, PDIP-28 package compatibility, standby current ≤100 µA, VPP = 12.0 V programming voltage, and integrated product identification code support for automated programming equipment.
Technical Context
The AT27C256R-55PI implements a standard OTP EPROM architecture with address decoding for 15-bit address bus (A0–A14), 8-bit bidirectional data bus (O0–O7), and two independent enable controls (CE and OE) enabling flexible bus interface timing. Its Rapid™ Programming Algorithm uses 100 µs CE pulses with VPP = 12.0 V and VCC = 6.5 V during programming, followed by verify cycles per byte.
It supports three operating modes: Read (CE=OE=low), Output Disable (CE=low, OE=high), and Standby (CE=high). The device integrates an on-chip product identification code accessed via A9=12.0 V and A0 toggling, returning manufacturer ID (0x1E) and device code (0x8C) - critical for programmer auto-detection and algorithm selection.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory Size | 256 Kbit (32,768 × 8 bits) - stores full firmware images for 8-bit microcontrollers without external memory expansion. |
| Read Access Time | 55 ns max (tACC) - enables direct interface with 12–16 MHz 8051, Z80, or 68K-family processors without wait states. |
| Supply Voltage | 5 V ±10% - compatible with legacy TTL/CMOS logic rails and eliminates need for auxiliary voltage regulators. |
| Standby Current | ≤100 µA (ISB1, CMOS CE input) - supports low-power sleep modes in battery-backed or energy-constrained systems. |
| Programming Voltage | VPP = 12.0 V ±0.5 V - requires dedicated programming supply; not compatible with standard 5 V-only programmers. |
| Operating Temp | –40°C to +85°C - qualified for industrial control, motor drives, and factory automation environments. |
| ESD Protection | 2,000 V HBM - ensures robustness during manual handling and board assembly without special ESD precautions. |
Pinout & Package
AT27C256R-55PI is supplied in a 28-lead, 0.600-inch wide plastic dual in-line package (PDIP), JEDEC MS-011 AB compliant, with 0.3 inch row spacing and through-hole mounting.
| 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 active only when CE=OE=low; high-impedance otherwise to prevent bus contention. |
| CE | Chip Enable | Active-low global enable; must be low for read or program access - used for memory-mapped decode or chip select gating. |
| OE | Output Enable | Active-low output control; allows CE assertion while holding outputs high-Z to avoid bus conflicts during shared-memory arbitration. |
| VPP | Programming Supply | 12.0 V input required only during programming; must be applied simultaneously with or after VCC and removed simultaneously or before VCC. |
| VCC | Power Supply | +5 V ±10% main supply; powers logic and outputs during read; supplies 6.5 V during programming when VPP = 13.0 V. |
| GND | Ground Reference | Signal and power return; requires local 0.1 µF ceramic decoupling capacitor placed within 5 mm of pins 14 and 28. |
| NC | No Connect | Pins 1 and 28 are unconnected in PDIP variant - no internal bonding; must remain floating or grounded per layout best practice. |
Key Features
| Feature | Design Value |
|---|---|
| Rapid™ Programming | 100 µs/byte typical programming time with automatic verify-reprogram loop - reduces production burn-in time by >70% vs. legacy EPROMs. |
| Integrated ID Code | Manufacturer ID (0x1E) and Device Code (0x8C) accessible via A9=12.0 V and A0 toggle - enables zero-configuration detection in universal programmers. |
| Two-Line Control | Independent CE and OE inputs allow precise bus timing control - eliminates need for external bus transceivers or glue logic in 8086/8051 systems. |
| High-Reliability CMOS | 200 mA latchup immunity and 2,000 V HBM ESD rating - ensures field reliability in electrically noisy industrial enclosures. |
| JEDEC Standard Packages | PDIP-28 pinout matches industry-standard 27C256 footprint - allows drop-in replacement of obsolete AMD, Intel, or ST equivalents without PCB redesign. |
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: Nonvolatile boot memory mapped at 0x0000–0x7FFF, accessed directly by 80C188 CPU during power-on reset sequence. Use Value: 55 ns tACC eliminates wait-state insertion, maintaining 12 MHz CPU throughput; industrial temp rating ensures operation inside 70°C control cabinets. | Use Scenario: Providing fixed startup code and peripheral initialization for Z80-based medical instrument controllers. IC Role / Device Role / Timing Role: Primary ROM executing cold-start vector fetch and hardware initialization before loading dynamic code from serial EEPROM. Use Value: CMOS/TTL compatibility guarantees signal integrity across mixed-logic designs; 100 µA standby current extends battery backup runtime during AC loss. |
| Automated Test Equipment BIOS | Point-of-Sale Terminal Kernel |
Use Scenario: Holding self-test routines and calibration constants in benchtop ATE platforms requiring field-upgradable firmware. IC Role / Device Role / Timing Role: Memory-mapped instruction store for test sequencer MCU, programmed once during manufacturing and verified via ID code. Use Value: Integrated product ID enables automated programming station verification; 2,000 V ESD protection prevents damage during technician rework cycles. | Use Scenario: Storing secure payment kernel and display driver initialization in retail POS terminals deployed in uncontrolled ambient environments. IC Role / Device Role / Timing Role: Fixed-code execution space for secure boot chain, isolated from writable flash to prevent malware injection. Use Value: Industrial temperature range (–40°C to +85°C) ensures reliable operation in non-climate-controlled retail spaces; PDIP-28 simplifies manual replacement in field service. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar OTP EPROM applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AM27C256B-55DC | Same 256K × 8 OTP EPROM, 55 ns tACC, but requires VPP = 21 V and lacks integrated ID code. | No automatic programmer detection; higher VPP demands more complex programming hardware. | Choose AM27C256B-55DC only if legacy programming infrastructure already supports 21 V VPP and ID code is unused. |
| MX27C256-55PC | Functionally identical timing and pinout, but rated only for commercial temp (0°C to 70°C) and specifies 150 µA max ISB. | Not suitable for industrial environments exceeding 70°C ambient or requiring <100 µA standby. | Select MX27C256-55PC only for cost-sensitive consumer-grade applications with controlled thermal environments. |
Compared with AM27C256B-55DC and MX27C256-55PC, the AT27C256R-55PI delivers verified industrial temperature operation, lower standby current, and integrated ID code - making it the preferred choice for new industrial designs requiring field-programmability assurance and long-term supply stability.
Availability
AT27C256R-55PI is available at Aetrix Electronics and suitable for industrial control systems, legacy microcontroller boot applications, and automated test equipment requiring stable component supply with guaranteed long-term availability.
Supply support for AT27C256R-55PI 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 firmware storage where OTP reliability, predictable timing, and JEDEC-standard footprint compatibility outweigh reprogrammability requirements.
FAQ
What is the maximum allowed VPP voltage for programming the AT27C256R-55PI?
The AT27C256R-55PI requires VPP = 12.0 V ± 0.5 V during programming, with absolute maximum rating of +14.0 V. Exceeding 12.5 V risks oxide damage and premature bit failure. The AT27C256R-55PI datasheet specifies VID = 11.5–12.5 V for product identification mode, confirming tight tolerance design. Always use a regulated, low-noise 12 V supply with local 0.1 µF ceramic decoupling at the VPP pin.
Can the AT27C256R-55PI operate with a 3.3 V supply?
No, the AT27C256R-55PI is specified only for 5 V ±10% operation (4.5 V to 5.5 V). Its input thresholds (VIL ≤ 0.8 V, VIH ≥ 2.0 V), output drive strength (IOL = 2.1 mA), and internal charge pumps require 5 V nominal. Using 3.3 V will result in undefined behavior, failed reads, and inability to enter programming mode. For 3.3 V systems, consider modern SPI NOR flash alternatives - the AT27C256R-55PI is not 3.3 V compatible.
Does the AT27C256R-55PI support page programming or only byte programming?
The AT27C256R-55PI supports only byte-level programming using the Rapid™ algorithm - each address is programmed individually with a 100 µs CE pulse, verified, and reprogrammed up to 10 times if needed. There is no page, sector, or burst programming mode. This design ensures deterministic write timing and eliminates risk of partial-page corruption. The AT27C256R-55PI does not implement any block-erase or multi-byte write functionality.
What is the purpose of the NC pins on the AT27C256R-55PI PDIP package?
In the AT27C256R-55PI's 28-lead PDIP package, pins 1 and 28 are designated No Connect (NC) - they have no internal bond wire and serve no electrical function. These pins must remain unconnected (floating) or may be tied to GND for mechanical stability; connecting them to VCC or signals violates the datasheet and may cause unpredictable behavior. This NC assignment is specific to the PDIP variant and differs from PLCC (pins 1 and 17 NC) and TSOP layouts.
How is the Integrated Product Identification Code accessed on the AT27C256R-55PI?
The AT27C256R-55PI ID code is accessed by setting A9 = 12.0 V (VID), holding A1–A14 = low, and toggling A0 between low (to read Manufacturer ID 0x1E) and high (to read Device Code 0x8C), with CE = OE = VIL and VCC = 5 V. This mode is electrically isolated from normal read operation and requires precise 12.0 V on A9 - the AT27C256R-55PI datasheet defines this as a dedicated identification protocol, not a memory-mapped register.
AT27C256R-55PI 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:
- 55 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-55PI FAQ
1.How can I place an order for AT27C256R-55PI through Aetrix?
Please submit a Request for Quotation (RFQ) for AT27C256R-55PI 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-55PI reliable?
The price and inventory of AT27C256R-55PI are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AT27C256R-55PI is usually 5 days.
3.What payment methods are accepted for AT27C256R-55PI?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AT27C256R-55PI transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AT27C256R-55PI?
AT27C256R-55PI orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AT27C256R-55PI 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-55PI?
For technical support, including AT27C256R-55PI datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AT27C256R-55PI requirements.
6.How does Aetrix verify that AT27C256R-55PI is sourced from the original manufacturer or authorized distributors?
All AT27C256R-55PI 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-55PI meets industry standards.
7.What is the process for return or replacement of AT27C256R-55PI?
All AT27C256R-55PI units undergo pre-shipment inspection (PSI). If there is an issue with AT27C256R-55PI, 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-55PI part is unused and in its original packaging.
Return procedure for AT27C256R-55PI:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
AT27C256R-55PI Tags
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