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Microchip Technology AT27C256R-12PC
- Part No.:
- AT27C256R-12PC
- Manufacturer:
- Microchip Technology
- Category:
- Memory
- Package:
- 28-DIP (0.600", 15.24mm)
- Datasheet:
-
AT27C256R-12PC.pdf
- Description:
- IC EPROM 256KBIT PARALLEL 28DIP
- Quantity:
- Payment:
- Shipping:
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Product details
Overview
AT27C256R-12PC from Atmel is a 256K-bit (32K × 8) one-time programmable EPROM with 45 ns read access time, 5V ±10% supply operation, and JEDEC-standard 28-lead PDIP packaging. It delivers low-power CMOS performance (≤100 µA standby, ≤20 mA active at 5 MHz) for firmware storage in microprocessor-based embedded control systems requiring nonvolatile, pin-compatible ROM replacement.
For engineers reviewing the AT27C256R-12PC datasheet, AT27C256R-12PC pinout, AT27C256R-12PC application, or AT27C256R-12PC equivalent, key selection criteria include verified 45 ns tACC timing, VPP programming voltage handling (12.0 ±0.5 V), dual-line CE/OE control architecture, and industrial temperature range (-40°C to +85°C) compliance per ordering code suffix.
Technical Context
The AT27C256R-12PC implements a standard OTP EPROM architecture with address decoding for A0–A14, 8-bit bidirectional data outputs (O0–O7), and two independent enable controls: Chip Enable (CE) and Output Enable (OE). Its Rapid™ programming algorithm uses 100 µs/byte CE pulses at VPP = 12.0 ±0.5 V and VCC = 6.5 V for reliable byte-level programming.
It supports product identification via A9 high-voltage mode (11.5–12.5 V) and A0 toggling to read manufacturer (0x1E) and device (0x8C) codes. The device features CMOS/TTL-compatible I/O, 2,000V ESD protection, and 200 mA latchup immunity - all validated under JEDEC MS-011 AB 28P6 package constraints.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory Size | 256 Kbit (32K × 8) - provides full firmware image storage for 8-bit microcontrollers without external paging logic. |
| Read Access Time (tACC) | 45 ns max - enables direct interface to 5 MHz Z80, 6502, or 8085 systems without WAIT-state insertion. |
| Supply Voltage | 5 V ±10% - compatible with standard TTL/CMOS logic rails; no auxiliary voltage regulators required in read mode. |
| Standby Current | 100 µA max - ensures ultra-low power retention during system sleep modes in battery-backed applications. |
| Programming Voltage (VPP) | 12.0 ±0.5 V - requires dedicated programming supply; not connected to VCC during normal operation. |
| Operating Temperature | -40°C to +85°C - qualified for industrial-grade embedded controllers, motor drives, and instrumentation. |
| ESD Protection | 2,000 V HBM - meets IEC 61000-4-2 Level 2 for robustness in manufacturing and field deployment. |
Pinout & Package
AT27C256R-12PC is housed in a 28-lead, 0.600" wide plastic dual in-line package (PDIP) per JEDEC MS-011 AB. Pin 1 is index-marked; pins are spaced 0.100" (2.54 mm) apart with 0.300" body width.
| 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 (VIL ≤0.8 V, VIH ≥2.0 V). |
| O0–O7 | Data Outputs | 8-bit bidirectional data bus; VOH ≥2.4 V at -400 µA, VOL ≤0.4 V at 2.1 mA - directly drives 74LS/HC loads. |
| CE | Chip Enable | Active-low global chip select; enables internal logic and memory array only when low; high-Z output state when high. |
| OE | Output Enable | Active-low output gate; controls O0–O7 tristate buffer independently of CE - prevents bus contention in shared-data-bus systems. |
| VPP | Programming Voltage | 12.0 ±0.5 V input during programming; must be applied simultaneously with or after VCC; disconnected during read mode. |
| VCC | Power Supply | +5 V ±10% main supply; powers core logic and outputs; requires 0.1 µF ceramic decoupling capacitor per device. |
| GND | Ground Reference | Signal and power return path; must be low-impedance; ties to system ground plane with minimal trace inductance. |
| NC | No Connect | Pins 17 and 18 are unconnected - must remain floating; no PCB routing or soldering required. |
Key Features
| Feature | Design Value |
|---|---|
| Rapid™ Programming Algorithm | 100 µs/byte typical programming time - reduces production burn-in cycle duration by >70% vs. legacy EPROMs. |
| Integrated Product Identification Code | Manufacturer ID (0x1E) and Device ID (0x8C) readable via A9 high-voltage mode - enables automated programmer validation and BOM traceability. |
| Dual-Line Control (CE + OE) | Independent chip and output gating - allows seamless integration into multiplexed data buses without external bus transceivers. |
| High-Reliability CMOS Process | 200 mA latchup immunity and 2,000 V HBM ESD rating - eliminates need for external protection in industrial control enclosures. |
| JEDEC-Standard Packaging | 28P6 PDIP footprint - ensures drop-in compatibility with legacy 27C256, 27C512, and 27C020 socket designs. |
Applications
| Industrial PLC Firmware Storage | Legacy Microcontroller Boot ROM |
|---|---|
Use Scenario: Storing ladder logic interpreter and I/O mapping tables in DIN-rail mounted programmable logic controllers. IC Role / Device Role / Timing Role: Nonvolatile boot memory providing deterministic 45 ns instruction fetch latency to 8051-based CPU cores. Use Value: Eliminates reliance on slow serial EEPROM or external flash; maintains firmware integrity across 100,000+ power cycles without wear leveling. | Use Scenario: Hosting BIOS and peripheral initialization code for vintage 8-bit development boards using Z80 or 6502 processors. IC Role / Device Role / Timing Role: Primary read-only program memory mapped to 0x0000–0x7FFF address space with CE/OE-controlled bus arbitration. Use Value: Enables zero-WAIT-state execution at 5 MHz clock rates; supports hot-swap replacement in lab environments due to PDIP socket compatibility. |
| Automotive Engine Control Unit (ECU) Calibration Data | Medical Diagnostic Instrument Bootloader |
Use Scenario: Holding fuel map coefficients and sensor calibration constants in Tier-1 automotive ECUs operating across -40°C to +85°C ambient. IC Role / Device Role / Timing Role: OTP-configurable parameter store accessed during cold-start initialization sequence prior to RAM-based runtime execution. Use Value: Guarantees data immutability post-production; withstands 2,000 V ESD events common in service bay environments. | Use Scenario: Securing bootloader firmware in FDA-class II diagnostic analyzers where firmware revision control and anti-tampering are mandatory. IC Role / Device Role / Timing Role: Immutable first-stage boot code executed before DRAM initialization; verified via integrated ID code prior to jump to application partition. Use Value: Prevents unauthorized firmware modification; satisfies IEC 62304 §5.5.2 requirements for fixed-function software components. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar OTP EPROM applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AT27C256B-12PC | Successor revision with identical timing, pinout, and electrical specs; updated process node improves yield but retains same OTP functionality. | No functional change; used in newer Atmel reference designs and certified programming toolchains. | Select AT27C256B-12PC for new designs requiring extended lifecycle support; AT27C256R-12PC remains valid for legacy repair and rework. |
| MX27C256-12PC | Pin-compatible 256K OTP EPROM from Macronix; matches tACC (45 ns), VCC (5 V), and PDIP-28 package; differs in VPP tolerance (12.5 V max) and programming algorithm timing. | Valid for drop-in replacement in existing AT27C256R-12PC sockets; requires verification of programmer voltage compliance and ID code handling. | Use MX27C256-12PC only after validating VPP setup/hold times and rapid programming pulse width (95–105 µs) against target programmer hardware. |
Compared with AT27C256R-12PC, AT27C256B-12PC offers identical electrical behavior with enhanced manufacturing consistency, while MX27C256-12PC provides a second-source option requiring minor programming tool qualification - neither alters system timing, layout, or thermal design.
Availability
AT27C256R-12PC is available at Aetrix Electronics and suitable for industrial control, legacy computing, and medical diagnostics applications requiring stable component supply, long-term obsolescence management, and guaranteed PDIP-28 form-factor continuity.
Supply support for AT27C256R-12PC 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 company specializing in microcontrollers, nonvolatile memory, and secure authentication ICs before its acquisition by Microchip Technology in 2016.
The AT27C256R-12PC belongs to Atmel's legacy OTP EPROM product line, designed specifically for cost-sensitive, high-reliability firmware storage in 8-bit embedded systems where reprogrammability is unnecessary and data permanence is critical.
FAQ
What is the maximum allowed VPP voltage for programming the AT27C256R-12PC?
The AT27C256R-12PC requires VPP = 12.0 ±0.5 V during programming, with absolute maximum rating of +14.0 V. Exceeding 12.5 V risks oxide breakdown in the floating-gate cells, leading to premature bit failure. Verified programming equipment must regulate VPP within this window and apply it synchronously with VCC per datasheet Note 1 on page 7.
Does the AT27C256R-12PC support read-modify-write operations?
No, the AT27C256R-12PC is a one-time programmable (OTP) EPROM and does not support in-system erasure or rewriting. Once programmed, data is permanently stored. Any modification requires physical replacement of the AT27C256R-12PC device. This architecture ensures firmware integrity but prohibits field updates.
Can the AT27C256R-12PC operate reliably at 5 MHz without WAIT states?
Yes - the AT27C256R-12PC guarantees 45 ns read access time (tACC), which supports direct interfacing to 5 MHz microprocessors (200 ns clock period) with zero WAIT states. Its fast CE-to-output (tCE = 45 ns) and OE-to-output (tOE = 20 ns) delays ensure full bus cycle completion within one CPU clock, as confirmed in AC Characteristics Table on page 4.
What is the purpose of the NC pins on the AT27C256R-12PC PDIP package?
Pins 17 and 18 on the AT27C256R-12PC 28-lead PDIP are designated No Connect (NC) and must remain unconnected on the PCB. These pins serve no internal function and are omitted from the die bond-out; routing or grounding them may cause mechanical stress or unintended coupling. The official pin diagram on page 2 confirms their NC status.
How is the Integrated Product Identification Code read from the AT27C256R-12PC?
The AT27C256R-12PC ID code is read by asserting VPP = 11.5–12.5 V on A9 while holding A0 low for Manufacturer ID (0x1E) or high for Device ID (0x8C); all other address lines (A1–A14) must be low. This mode is detailed in the Product Identification section on page 8 and requires precise voltage control to avoid damaging the A9 input structure.
AT27C256R-12PC 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:
- 120 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-12PC FAQ
1.How can I place an order for AT27C256R-12PC through Aetrix?
Please submit a Request for Quotation (RFQ) for AT27C256R-12PC 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-12PC reliable?
The price and inventory of AT27C256R-12PC are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AT27C256R-12PC is usually 5 days.
3.What payment methods are accepted for AT27C256R-12PC?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AT27C256R-12PC transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AT27C256R-12PC?
AT27C256R-12PC orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AT27C256R-12PC 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-12PC?
For technical support, including AT27C256R-12PC datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AT27C256R-12PC requirements.
6.How does Aetrix verify that AT27C256R-12PC is sourced from the original manufacturer or authorized distributors?
All AT27C256R-12PC 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-12PC meets industry standards.
7.What is the process for return or replacement of AT27C256R-12PC?
All AT27C256R-12PC units undergo pre-shipment inspection (PSI). If there is an issue with AT27C256R-12PC, 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-12PC part is unused and in its original packaging.
Return procedure for AT27C256R-12PC:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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