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Microchip Technology AT27C256R-70PC
- Part No.:
- AT27C256R-70PC
- Manufacturer:
- Microchip Technology
- Category:
- Memory
- Package:
- 28-DIP (0.600", 15.24mm)
- Datasheet:
-
AT27C256R-70PC.pdf
- Description:
- IC EPROM 256KBIT PARALLEL 28DIP
- Quantity:
- Payment:
- Shipping:
Inventory:1,731
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Product details
Overview
AT27C256R-70PC from Atmel is a 32K × 8-bit one-time programmable EPROM (OTP EPROM) with 45 ns read access time, 5V ±10% supply operation, and JEDEC-standard 28-lead PDIP packaging. It delivers fast, low-power nonvolatile storage for firmware boot code in microprocessor systems requiring deterministic timing and no wait states.
For engineers reviewing the AT27C256R-70PC datasheet, AT27C256R-70PC pinout, AT27C256R-70PC application, or AT27C256R-70PC equivalent, key selection criteria include verified 70 ns tACC timing grade, industrial temperature range support (-40°C to +85°C), VPP programming voltage requirement (12.0 V ±0.5 V), and dual-line control (CE/OE) architecture for bus contention management.
Technical Context
The AT27C256R-70PC implements a CMOS-based OTP EPROM array with address decoding logic, output buffers, and two independent enable controls (CE and OE). Its Rapid™ Programming Algorithm enables 100 µs/byte typical programming with on-chip verification loops and supports product identification via A9/VH and A0 toggling.
It operates in five distinct modes-Read, Output Disable, Standby, Rapid Program, and PGM Verify-each defined by specific CE, OE, and VPP voltage combinations. The device features integrated ESD protection (2,000 V) and latchup immunity (200 mA), and requires external decoupling: 0.1 µF ceramic capacitor at VCC–GND plus optional 4.7 µF bulk capacitor for EPROM arrays.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory Size | 256 Kbit (32K × 8), fixed parallel organization for direct CPU address/data bus interfacing |
| Read Access Time (tACC) | 70 ns max - guarantees sub-14 MHz microprocessor interface without WAIT states |
| VCC Supply | 5 V ±10% - compatible with standard TTL/CMOS logic rails; no auxiliary voltage required for read mode |
| Standby Current (ISB1) | 100 µA max - enables ultra-low power retention in battery-backed or sleep-mode systems |
| Active Current (ICC) | 20 mA max at 5 MHz - defines thermal and supply design margin for sustained read bursts |
| VPP Programming Voltage | 12.0 V ±0.5 V - required only during programming; must be applied after VCC and removed before VCC |
| Operating Temperature | -40°C to +85°C - qualified for industrial environments including factory automation and motor control |
Pinout & Package
AT27C256R-70PC is packaged in a 28-lead, 0.600-inch wide plastic dual in-line package (PDIP), per JEDEC MS-011 AB standard. Pin 1 is index-marked; pins are numbered counter-clockwise from top-left corner when viewed from top with notch up.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| A0–A14 | Address Inputs | 15-bit address bus accepting 0–32767; latched internally on CE transition for memory location selection |
| O0–O7 | Data Outputs | 8-bit bidirectional data bus (output-only in read mode); TTL/CMOS-compatible drive strength (IOL = 2.1 mA, IOH = -400 µA) |
| CE | Chip Enable | Primary device select; active-low; controls internal array power and output drivers; used for rapid programming pulse |
| OE | Output Enable | Secondary output gate; active-low; allows multiple devices on same data bus without contention when CE is asserted |
| VPP | Programming Voltage | 12 V input required only during programming; must be decoupled with 0.1 µF capacitor to ground |
| VCC | Power Supply | +5 V main supply; powers all logic and memory array; must be stable before VPP application |
| GND | Ground Reference | Signal and power return; decoupling capacitor must connect directly between VCC and this pin |
| NC | No Connect | Pins 1 and 17 in PLCC variant are NC, but PDIP version has no NC pins - all 28 pins are functional |
Key Features
| Feature | Design Value |
|---|---|
| Rapid™ Programming Algorithm | 100 µs/byte typical programming time with automatic verify/reprogram loop - reduces production programming cycle time by >5× vs legacy EPROMs |
| Integrated Product Identification Code | Manufacturer ID (0x1E) and Device Code (0x8C) readable via A9=12 V and A0 toggle - enables automated programmer validation and BOM traceability |
| Two-Line Control Architecture | Independent CE and OE enables hierarchical bus arbitration - supports multi-device memory maps without external logic |
| High-Reliability Process | 2,000 V HBM ESD rating and 200 mA latchup immunity - ensures robustness in manufacturing handling and field deployment |
| JEDEC-Standard Packaging Options | 28-lead PDIP (AT27C256R-70PC), SOIC, TSOP, and 32-lead PLCC - simplifies PCB redesign across form factors |
Applications
| Industrial PLC Firmware Storage | Legacy PC BIOS Boot ROM |
|---|---|
Use Scenario: Storing ladder logic firmware and I/O configuration tables in programmable logic controllers deployed in factory-floor environments with ambient temperatures up to +85°C. IC Role / Device Role / Timing Role: Nonvolatile boot memory mapped to CPU address space; provides deterministic 70 ns read latency to meet real-time scan-cycle deadlines. Use Value: Eliminates reliance on slow serial EEPROM or flash; avoids WAIT states in 80C186/80C188-based control CPUs; withstands industrial EMI and thermal cycling. | Use Scenario: Holding POST routines and hardware initialization code in ISA-bus desktop motherboards from the early 1990s. IC Role / Device Role / Timing Role: Primary boot ROM accessed at reset vector (0xFFFF0h); decoded via 74LS138 and enabled by chipset-generated CE/OE signals. Use Value: Guarantees <70 ns instruction fetch timing under worst-case VCC and temperature; supports TTL-level bus loading without buffers. |
| Automotive Engine Control Unit (ECU) Calibration Data | Medical Diagnostic Equipment Bootloader |
Use Scenario: Storing fuel map calibration constants and sensor lookup tables in pre-OBD-II engine control modules operating at -40°C to +125°C. IC Role / Device Role / Timing Role: Read-only configuration store accessed during cold start; isolated from volatile RAM by dedicated address decode logic. Use Value: Immune to radiation-induced bit flips; retains data over 20+ year vehicle lifetime; qualified for automotive temp range in PA-grade variants. | Use Scenario: Hosting secure bootloader firmware in FDA-cleared diagnostic imaging systems where firmware integrity is critical for regulatory compliance. IC Role / Device Role / Timing Role: Immutable first-stage loader executed before DRAM initialization; verified via checksum prior to handoff to application code. Use Value: One-time programmability prevents accidental overwrite or malware injection; 2,000 V ESD rating protects against ESD events during service technician handling. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar OTP EPROM applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AT27C256B-70PC | Successor revision with improved AC timing margins and tighter VIL/VIH thresholds; identical pinout and programming algorithm | Same industrial temperature range and PDIP package; supports higher noise immunity in electrically noisy medical/industrial settings | Select when new designs require enhanced DC noise rejection or long-term Atmel product continuity beyond AT27C256R lifecycle |
| MX27C256-70PC | Macronix second-source part; identical 32K×8 organization, 70 ns tACC, and PDIP-28 footprint; requires same VPP voltage and programming sequence | Validated drop-in replacement per JESD46; suitable for dual-sourcing strategies in high-volume industrial OEMs | Choose for supply chain diversification while maintaining full functional and layout compatibility |
Compared with AT27C256R-70PC, AT27C256B-70PC offers tighter input threshold specs for noise margin, while MX27C256-70PC provides identical functionality with dual-source assurance-both retain the same 70 ns timing grade, industrial temperature rating, and PDIP-28 mechanical fit.
Availability
AT27C256R-70PC is available at Aetrix Electronics and suitable for industrial control systems, legacy computing platforms, automotive ECU calibration storage, and medical diagnostic equipment requiring stable component supply across extended product lifecycles.
Supply support for AT27C256R-70PC 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 was a U.S.-based semiconductor manufacturer specializing in microcontrollers, nonvolatile memory, and security ICs before its acquisition by Microchip Technology in 2016.
The AT27C256R belongs to Atmel's legacy OTP EPROM product line, designed specifically for cost-sensitive, high-reliability firmware storage in microprocessor-based systems where reprogrammability is unnecessary and data permanence is critical.
FAQ
What is the maximum allowed VPP voltage for programming the AT27C256R-70PC?
The AT27C256R-70PC requires a VPP programming voltage of 12.0 V ±0.5 V, meaning the absolute maximum is 12.5 V. Exceeding this value risks permanent damage to the oxide layers in the EPROM cells. The datasheet specifies that VPP must be applied after VCC and removed before VCC to prevent overstress conditions. This constraint is strictly enforced in certified programming equipment used for AT27C256R-70PC.
Does the AT27C256R-70PC support read operations at 3.3 V?
No, the AT27C256R-70PC does not support 3.3 V read operation. Its VCC specification is strictly 5 V ±10%, and all DC and AC characteristics-including VOL, VOH, tACC, and input thresholds-are guaranteed only within that range. Attempting to operate the AT27C256R-70PC at 3.3 V will result in undefined outputs, timing violations, and potential data corruption. Level-shifting circuitry is required for interfacing with 3.3 V systems.
Can the AT27C256R-70PC be reprogrammed after initial programming?
No, the AT27C256R-70PC is a one-time programmable (OTP) EPROM. Once a memory cell is programmed (by Fowler-Nordheim tunneling during VPP application), it cannot be erased or rewritten. There is no UV erasure window or electrical erase mechanism. The "R" suffix denotes the Rapid™ programming variant, not reprogrammability. Any attempt to reprogram an already-programmed AT27C256R-70PC may cause cell degradation but will not restore original data.
What decoupling capacitors are required for stable operation of the AT27C256R-70PC?
The AT27C256R-70PC requires a minimum 0.1 µF high-frequency ceramic capacitor placed directly between VCC and GND, with leads as short as possible. For systems containing multiple AT27C256R-70PC devices or large EPROM arrays, a 4.7 µF bulk electrolytic capacitor is also recommended near the power entry point. These values are specified in the "System Considerations" section of the AT27C256R-70PC datasheet to suppress transient excursions during CE switching.
How is the Integrated Product Identification Code read from the AT27C256R-70PC?
The Integrated Product Identification Code of the AT27C256R-70PC is read by setting A9 to 12.0 V ±0.5 V (VH), holding A1–A14 low (VIL), and toggling A0: low selects the Manufacturer ID byte (0x1E), high selects the Device Code byte (0x8C). Both bytes appear on O7–O0 during a standard read cycle with CE and OE asserted. This feature is used by industry-standard programmers to auto-detect the AT27C256R-70PC and apply correct programming algorithms.
AT27C256R-70PC 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:
- 70 ns
- Voltage - Supply:
- 4.5V ~ 5.5V
- Operating Temperature:
- 0°C ~ 70°C (TC)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 28-PDIP
AT27C256R-70PC FAQ
1.How can I place an order for AT27C256R-70PC through Aetrix?
Please submit a Request for Quotation (RFQ) for AT27C256R-70PC 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-70PC reliable?
The price and inventory of AT27C256R-70PC are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AT27C256R-70PC is usually 5 days.
3.What payment methods are accepted for AT27C256R-70PC?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AT27C256R-70PC transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AT27C256R-70PC?
AT27C256R-70PC orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AT27C256R-70PC 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-70PC?
For technical support, including AT27C256R-70PC datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AT27C256R-70PC requirements.
6.How does Aetrix verify that AT27C256R-70PC is sourced from the original manufacturer or authorized distributors?
All AT27C256R-70PC 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-70PC meets industry standards.
7.What is the process for return or replacement of AT27C256R-70PC?
All AT27C256R-70PC units undergo pre-shipment inspection (PSI). If there is an issue with AT27C256R-70PC, 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-70PC part is unused and in its original packaging.
Return procedure for AT27C256R-70PC:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
AT27C256R-70PC 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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93LC46BT-I/OT
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24LC01BT-I/SN
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