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Microchip Technology AT27C256R-90PC
- Part No.:
- AT27C256R-90PC
- Manufacturer:
- Microchip Technology
- Category:
- Memory
- Package:
- 28-DIP (0.600", 15.24mm)
- Datasheet:
-
AT27C256R-90PC.pdf
- Description:
- IC EPROM 256KBIT PARALLEL 28DIP
- Quantity:
- Payment:
- Shipping:
Inventory:4,688
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Product details
Overview
AT27C256R-90PC 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 low-power active current (20 mA max at 5 MHz) and standby current (100 µA max), enabling reliable firmware storage in microprocessor systems without wait states.
For engineers reviewing the AT27C256R-90PC datasheet, AT27C256R-90PC pinout, AT27C256R-90PC application, or AT27C256R-90PC equivalent, key selection criteria include verified 45 ns tACC timing, VPP programming voltage requirements (12.0 V ±0.5 V), dual-line control (CE/OE), integrated product identification code, and industrial temperature range support (-40°C to +85°C).
Technical Context
The AT27C256R-90PC implements a CMOS-based OTP EPROM architecture with two-line enable control (CE and OE) to prevent bus contention during read cycles. Its address decoding supports A0–A14 (15-bit), enabling full 32K-byte access, while output drivers are TTL/CMOS compatible with VOH ≥ 2.4 V and VOL ≤ 0.4 V under specified loads.
Programming uses the Rapid™ algorithm with 100 µs/byte typical pulse width at VPP = 12.0 V ±0.5 V and VCC = 6.5 V ±0.25 V. Product identification is accessed via A9 high-voltage mode (11.5–12.5 V) and A0 toggling to select manufacturer (0x1E) or device code (0x8C) bytes.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory Size | 256 Kbit (32K × 8), sufficient for boot code or fixed firmware in 8-bit microcontroller systems |
| Read Access Time | 45 ns max (tACC), eliminates WAIT states on 5 MHz Z80, 8086, or 68000-based designs |
| Supply Voltage | 5 V ±10%, compatible with standard TTL/CMOS logic rails without regulation overhead |
| Active Current | 20 mA max at 5 MHz, enables low-thermal-load integration in dense PCB layouts |
| Standby Current | 100 µA max (CMOS CE mode), supports low-power hold states in battery-backed systems |
| Programming Voltage | VPP = 12.0 V ±0.5 V, requires dedicated programming circuitry-not compatible with standard 5 V-only systems |
| ESD Protection | 2,000 V HBM, reduces risk of handling damage during manual programming or board assembly |
| Latchup Immunity | 200 mA, prevents destructive latchup during transient overvoltage events on I/O or supply pins |
Pinout & Package
AT27C256R-90PC is packaged in a 28-lead, 0.600" wide plastic dual-inline package (PDIP), per JEDEC MS-011 AB standard. Pin 1 is index-marked; pins 1–14 and 15–28 occupy opposing sides with GND (pin 14) and VCC (pin 28) positioned for decoupling.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| A0–A14 | Address Inputs | 15-bit address bus interface; fully decoded to access any of 32,768 bytes without external logic |
| O0–O7 | Data Outputs | 8-bit bidirectional data bus outputs; TTL/CMOS-compatible drive strength supports direct connection to microprocessor data lines |
| CE | Chip Enable | Primary device select; must be low for read or program operations; controls power state transition between active and standby |
| OE | Output Enable | Secondary output gate; allows shared bus operation by disabling outputs while CE remains asserted |
| VPP | Programming Voltage | 12 V input required only during programming; must be applied simultaneously with or after VCC to avoid damage |
| GND | Ground Reference | PIN 14; serves as return path for all internal logic and I/O; requires local 0.1 µF ceramic decoupling |
| VCC | Power Supply | PIN 28; 5 V ±10% supply for read/standby; elevated to 6.5 V during programming per spec |
| NC | No Connect | No internal connection; must remain unconnected-no pull-up/down or routing allowed |
Key Features
| Feature | Design Value |
|---|---|
| Rapid™ Programming Algorithm | 100 µs/byte typical programming time enables high-throughput firmware loading in production programming stations |
| Integrated Product Identification Code | Manufacturer ID (0x1E) and Device Code (0x8C) accessible via A9 high-voltage mode, ensuring automatic algorithm selection in certified programmers |
| Dual-Line Control (CE/OE) | Independent chip and output enables allow flexible bus arbitration and eliminate contention in multi-device memory maps |
| Three Temperature Ranges | Industrial (-40°C to +85°C) rating confirmed for AT27C256R-90PI/PC variants, supporting deployment in factory automation and motor control environments |
| JEDEC-Standard Packaging | 28P6 PDIP footprint ensures compatibility with legacy sockets, wave-soldering fixtures, and automated test handlers |
Applications
| Embedded Boot ROM | Industrial PLC Firmware Storage |
|---|---|
Use Scenario: Storing immutable boot code for 8-bit microcontrollers (e.g., 8051, Z8) in cost-sensitive consumer electronics. IC Role / Device Role / Timing Role: Nonvolatile instruction memory mapped into CPU address space; accessed at power-on reset with no initialization delay. Use Value: 45 ns tACC ensures zero-wait-state execution on 5 MHz buses, reducing boot latency and eliminating external wait-state generators. | Use Scenario: Holding firmware and configuration tables in programmable logic controllers operating in factory-floor environments. IC Role / Device Role / Timing Role: Field-upgradeable program memory; programmed once during manufacturing using industrial-grade programmers. Use Value: Industrial temperature rating (-40°C to +85°C) and 200 mA latchup immunity ensure reliability amid electrical noise and thermal cycling in control cabinets. |
| Military Communications Module | Legacy Test Equipment Calibration Data |
Use Scenario: Securing cryptographic keys or protocol stacks in ruggedized tactical radios requiring tamper-resistant nonvolatile storage. IC Role / Device Role / Timing Role: One-time programmable memory preventing post-deployment modification; accessed via discrete address/data bus. Use Value: 2,000 V ESD protection and -40°C to +125°C automotive-grade variants (AT27C256R-90PA) support MIL-STD-810G environmental compliance. | Use Scenario: Storing factory-calibrated ADC/DAC coefficients and sensor linearization tables in benchtop multimeters and signal analyzers. IC Role / Device Role / Timing Role: Read-only calibration memory mapped to fixed I/O space; accessed during self-test sequences. Use Value: Integrated product ID code enables automated calibration file binding in test software, preventing mismatched firmware/data pairs. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar OTP EPROM applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AT27C256B-90PC | Successor revision with identical pinout, timing, and programming specs; improved process yield and tighter ICC tolerance (8 mA typical vs. 20 mA max) | Same use cases; preferred for new designs due to enhanced reliability and lower active power | Select AT27C256B-90PC when sourcing new production builds; AT27C256R-90PC remains valid for legacy repair or obsolescence mitigation |
| MX27C256-90PC | Pin-compatible 256K OTP EPROM; same 28P6 PDIP, 45 ns tACC, and 5 V supply-but lacks integrated product ID and Rapid™ programming support | Requires external programming algorithm selection; not supported by auto-ID-capable programmers (e.g., BP Microsystems) | Choose MX27C256-90PC only if existing programming infrastructure does not rely on ID-code verification or rapid pulse programming |
Compared with AT27C256R-90PC, the AT27C256B-90PC offers lower typical active current and higher production yield, while MX27C256-90PC trades integrated ID and programming speed for broader second-source availability-making it suitable only where those features are unused.
Availability
AT27C256R-90PC is available at Aetrix Electronics and suitable for embedded boot ROM, industrial PLC firmware storage, military communications module, and legacy test equipment calibration data applications requiring stable component supply across extended lifecycle windows.
Supply support for AT27C256R-90PC 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, designed high-reliability nonvolatile memory and microcontroller solutions for industrial, automotive, and defense applications.
The AT27C256R belongs to Atmel's OTP EPROM product line, engineered for cost-effective, secure, and field-immutable firmware storage in systems where reprogrammability is unnecessary and data integrity is critical.
FAQ
What is the maximum read access time specification for AT27C256R-90PC?
The AT27C256R-90PC has a maximum read access time (tACC) of 45 ns under standard conditions (VCC = 5 V ±10%, TA = 25°C, CL = 30 pF). This value is guaranteed across the industrial temperature range (-40°C to +85°C) and enables zero-wait-state operation with 5 MHz microprocessors. The "-90" suffix denotes this speed grade; faster variants (e.g., -45) exist but are not applicable to AT27C256R-90PC.
Can AT27C256R-90PC be used with a 3.3 V system?
No, AT27C256R-90PC requires a 5 V ±10% supply (4.5 V to 5.5 V) for both read and standby operation, and 12.0 V ±0.5 V on VPP during programming. It is not 3.3 V tolerant: VIH minimum is 2.0 V, but VCC must be 5 V, and interfacing with 3.3 V logic requires level-shifting circuitry on all address, data, and control lines to prevent damage or incorrect reads.
Does AT27C256R-90PC support in-circuit programming?
No, AT27C256R-90PC does not support in-circuit programming. It requires VPP = 12.0 V ±0.5 V applied externally during programming, which is incompatible with standard 5 V system rails. Programming must be performed in a dedicated socketed programmer with proper VPP sequencing (VCC applied before/with VPP, removed after/with VPP) and 0.1 µF VPP-to-GND decoupling.
What is the purpose of the NC pin on AT27C256R-90PC?
The NC (No Connect) pin on AT27C256R-90PC-pin 27 in the 28P6 PDIP package-has no internal connection and must remain unconnected. It is not a ground or voltage reference; routing traces to or placing components near this pin may cause parasitic coupling or mechanical interference. The datasheet explicitly prohibits connecting NC pins to any net, including GND or VCC.
How is the Integrated Product Identification Code accessed on AT27C256R-90PC?
The Integrated Product Identification Code on AT27C256R-90PC is accessed by setting A9 to VH = 12.0 V ±0.5 V while holding A1–A14 low (VIL), then toggling A0: low selects the Manufacturer ID byte (0x1E), high selects the Device Code byte (0x8C). This mode requires precise high-voltage control and is used exclusively by certified programming equipment to auto-detect device type and apply correct algorithms.
AT27C256R-90PC 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:
- 90 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-90PC FAQ
1.How can I place an order for AT27C256R-90PC through Aetrix?
Please submit a Request for Quotation (RFQ) for AT27C256R-90PC 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-90PC reliable?
The price and inventory of AT27C256R-90PC are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AT27C256R-90PC is usually 5 days.
3.What payment methods are accepted for AT27C256R-90PC?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AT27C256R-90PC transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AT27C256R-90PC?
AT27C256R-90PC orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AT27C256R-90PC 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-90PC?
For technical support, including AT27C256R-90PC datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AT27C256R-90PC requirements.
6.How does Aetrix verify that AT27C256R-90PC is sourced from the original manufacturer or authorized distributors?
All AT27C256R-90PC 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-90PC meets industry standards.
7.What is the process for return or replacement of AT27C256R-90PC?
All AT27C256R-90PC units undergo pre-shipment inspection (PSI). If there is an issue with AT27C256R-90PC, 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-90PC part is unused and in its original packaging.
Return procedure for AT27C256R-90PC:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
AT27C256R-90PC Tags
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