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STMicroelectronics M27C256B-12F1
- Part No.:
- M27C256B-12F1
- Manufacturer:
- STMicroelectronics
- Category:
- Memory
- Package:
- 28-CDIP (0.600", 15.24mm) Window
- Datasheet:
-
M27C256B-12F1.pdf
- Description:
- IC EPROM 256KBIT PARALLEL 28CDIP
- Quantity:
- Payment:
- Shipping:
Inventory:1,700
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Product details
Overview
M27C256B-12F1 from STMicroelectronics is a 256 Kbit (32K × 8) UV-erasable EPROM in FDIP28W ceramic window package, featuring 45 ns access time, 5V ±10% read supply, and electronic signature (20h/8Dh) for automated programming validation. It serves as non-volatile program storage in legacy microprocessor systems requiring field-erasable firmware updates via UV exposure.
For engineers reviewing the M27C256B-12F1 datasheet, M27C256B-12F1 pinout, M27C256B-12F1 application, or M27C256B-12F1 equivalent, this device requires attention to VPP=12.75V programming voltage, dual-line control (E/G), A9 high-voltage electronic signature activation, and UV erasure logistics - not standard flash replacement.
Technical Context
The M27C256B-12F1 implements TTL-compatible address/data interfaces with two independent enable controls: Chip Enable (E) for power gating and Output Enable (G) for output bus isolation. Its architecture supports parallel programming of bytes using Q0–Q7 as bidirectional data lines under VPP = 12.75V ±0.25V and VCC = 6.25V ±0.25V.
Electronic signature mode activates at 11.5–12.5V on A9 (with VCC = VPP = 5V), outputting manufacturer code 20h and device code 8Dh on Q7–Q0. Erasure requires ≥15 W·s/cm² UV dose at 2537 Å wavelength, achievable in 15–20 min at ≤2.5 cm distance from unfiltered lamp.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory Size | 256 Kbit (32,768 × 8), fixed parallel organization - no address multiplexing or internal refresh required. |
| Access Time | 45 ns (tAVQV), defines maximum clock rate for synchronous read cycles in microprocessor bus timing. |
| VCC Supply | 5V ±10% during read - compatible with legacy 5V TTL/CMOS systems without regulation overhead. |
| VPP Voltage | 12.75V ±0.25V for programming - mandates external high-voltage generator, not supplied by host system. |
| Standby Current | 100 µA (CMOS E-high) - enables low-power retention in battery-backed or intermittent-use embedded controllers. |
| Programming Time | 100 µs per word - determines minimum firmware update duration; PRESTO II algorithm guarantees margin without overprogramming. |
| Operating Temp | –40°C to +125°C - validated for industrial/military-grade environments where plastic-packaged OTP variants fail. |
Pinout & Package
FDIP28W (28-pin ceramic frit-seal DIP with UV-transparent window) - hermetically sealed for long-term data retention and repeatable UV erasure. Dimensions: 36.9 mm × 15.2 mm × 4.3 mm (L×W×H), 2.54 mm lead pitch.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| A0–A14 | Address Inputs | 15-bit address bus (32K locations); A9 used at 12V for electronic signature - must be isolated during normal operation. |
| Q0–Q7 | Data I/O Terminals | Bidirectional: outputs during read/verify, inputs during programming - require external pull-ups and level-shifting for safe 12V tolerance. |
| E | Chip Enable | Active-low primary selection signal; drives device into standby (100 µA) when high - critical for multi-chip memory banking. |
| G | Output Enable | Active-low secondary control; gates Q0–Q7 drivers independently of E - prevents bus contention in shared-data-bus systems. |
| VPP | Programming Supply | 12.75V input only during programming/verify; must be applied after VCC and removed before VCC - violation causes permanent damage. |
| VCC | Supply Voltage | 5V ±10% for read; 6.25V ±0.25V for programming - dual-voltage requirement mandates separate regulator or switching circuitry. |
| VSS | Ground Reference | Common return for all signals; requires dedicated low-inductance 0.1 µF ceramic decoupling adjacent to pin 14. |
| NC / DU | No Connect / Don't Use | Pins 10, 20 (NC) and 9, 25 (DU) are internally unconnected - must remain floating or grounded per layout guidelines to avoid noise coupling. |
Key Features
| Feature | Design Value |
|---|---|
| UV Erasability | Full array erasure via 2537 Å UV light in 15–20 min - enables firmware revision cycles without component replacement in field-deployed equipment. |
| Electronic Signature | Manufacturer code 20h and device code 8Dh readable at A9=12V - allows programming tools to auto-select correct algorithm and prevent misprogramming. |
| Two-Line Control (E + G) | Independent chip select and output gating - eliminates bus contention in multi-EPROM systems and reduces active power by >99% during idle cycles. |
| PRESTO II Programming | Guaranteed margin programming with 100 µs pulses and automatic verify - eliminates need for iterative overprogram cycles and improves yield in production programming. |
| Extended Temperature Range | –40°C to +125°C operation - qualified for engine control units, avionics subsystems, and industrial PLCs where commercial-grade EPROMs derate. |
Applications
| Industrial PLC Firmware Storage | Avionics Boot ROM |
|---|---|
|
Use Scenario: Storing ladder logic interpreter and I/O configuration in programmable logic controllers deployed in factory automation cabinets. IC Role / Device Role / Timing Role: Non-volatile program memory mapped to CPU address space; accessed via 8-bit data bus with E/G-controlled timing windows. Use Value: UV erasability permits field updates of control algorithms without board removal; 125°C rating ensures reliability near motor drives and power converters. |
Use Scenario: Holding boot firmware for flight management computers in certified aircraft systems requiring traceable, tamper-resistant memory. IC Role / Device Role / Timing Role: Primary boot ROM executing on power-up; timing-critical 45 ns access supports deterministic initialization sequences. Use Value: Ceramic FDIP28W package provides hermetic sealing and radiation tolerance absent in plastic OTP variants - critical for DO-254 compliance. |
| Legacy Test Equipment Calibration Data | Military Radio Firmware |
|
Use Scenario: Storing calibration coefficients and sensor linearization tables in benchtop oscilloscopes and spectrum analyzers. IC Role / Device Role / Timing Role: Read-only data store accessed during self-test; standby current <100 µA extends battery life in portable units. Use Value: Electronic signature (20h/8Dh) validates authenticity during recalibration - prevents counterfeit or mismatched firmware loading. |
Use Scenario: Securing cryptographic key loading routines and secure boot loaders in tactical HF/VHF radios operating in extreme environmental conditions. IC Role / Device Role / Timing Role: Tamper-evident firmware vault; UV window allows physical verification of erasure prior to rekeying operations. Use Value: –40°C to +125°C rating and ceramic package withstand thermal shock during rapid desert-to-mountaintop deployment transitions. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar EPROM-based firmware storage applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AM27C256B-120DC | Same 256K×8 organization and 45 ns speed, but AMD-manufactured with different electronic signature (01h/8Dh) and 12.5V VPP tolerance. | Requires revalidation of programming tool voltage profiles and signature detection logic; identical FDIP28W footprint. | Select only if existing AMD-based programming infrastructure is in place - not drop-in due to VPP and signature mismatches. |
| M27C256B-12B6 | Identical silicon but in PDIP28 plastic package (no UV window); same 45 ns speed, 5V/12.75V specs, and -40°C to +85°C rating. | Eliminates UV erasure capability - suitable only for one-time-programmed applications where field updates are unnecessary. | Choose for cost-sensitive industrial controls where firmware is frozen post-production and ceramic packaging adds no value. |
Compared with AM27C256B-120DC, M27C256B-12F1 offers guaranteed STMicroelectronics process consistency and full military temperature support; versus M27C256B-12B6, it trades erasability for extended thermal range and hermetic reliability - critical for aerospace and high-reliability deployments.
Availability
M27C256B-12F1 is available at Aetrix Electronics and suitable for industrial PLC firmware storage, avionics boot ROM, and military radio firmware requiring stable component supply across extended lifecycle programs.
Supply support for M27C256B-12F1 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
STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, specializing in automotive, industrial, and power management ICs with vertical manufacturing control.
The M27C256B belongs to ST's legacy EPROM product line designed for high-reliability, field-upgradable firmware storage in systems where flash endurance or security features are secondary to proven UV-erasable stability and wide-temperature operation.
FAQ
What UV wavelength and exposure time are required to fully erase M27C256B-12F1?
Full erasure requires short-wave ultraviolet light at 2537 Å wavelength with a minimum integrated dose of 15 W·s/cm². Using a standard 12,000 µW/cm² UV lamp placed ≤2.5 cm from the FDIP28W window, erasure completes in 15–20 minutes. Fluorescent ambient light may cause partial erasure over years - opaque window labels are recommended for long-term storage.
Can M27C256B-12F1 be programmed with standard 5V logic levels?
No. Programming requires VPP = 12.75V ±0.25V applied to pin 28, VCC = 6.25V ±0.25V (not 5V), and A9 driven to 11.5–12.5V for electronic signature verification. Standard 5V microcontrollers cannot directly drive these voltages - dedicated EPROM programmers or discrete HV generation circuitry are mandatory.
Is the FDIP28W package RoHS-compliant?
The M27C256B-12F1 FDIP28W package contains leaded solder in its ceramic-to-metal seal and is not RoHS-compliant. STMicroelectronics discontinued RoHS conversion for this legacy UV EPROM family; compliant alternatives require migration to modern flash or EEPROM solutions with different footprints and protocols.
How does the two-line control (E and G) improve system-level reliability?
E (Chip Enable) places the device in ultra-low-power standby (100 µA), cutting active current by 300×, while G (Output Enable) independently disables outputs to prevent bus contention during memory arbitration. This separation ensures that deselected chips draw negligible power and never drive conflicting logic states - essential for stable multi-chip memory banks in real-time control systems.
M27C256B-12F1 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- STMicroelectronics
- Series:
- -
- Package/Case:
- 28-CDIP (0.600", 15.24mm) Window
- Packaging:
- Tube
- Product Status:
- Obsolete
- Programmable:
- Not Verified
- Memory Type:
- Non-Volatile
- Memory Format:
- EPROM
- Technology:
- EPROM - UV
- 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 (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 28-CDIP Frit Seal with Window
M27C256B-12F1 FAQ
1.How can I place an order for M27C256B-12F1 through Aetrix?
Please submit a Request for Quotation (RFQ) for M27C256B-12F1 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 M27C256B-12F1 reliable?
The price and inventory of M27C256B-12F1 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for M27C256B-12F1 is usually 5 days.
3.What payment methods are accepted for M27C256B-12F1?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for M27C256B-12F1 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for M27C256B-12F1?
M27C256B-12F1 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your M27C256B-12F1 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 M27C256B-12F1?
For technical support, including M27C256B-12F1 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your M27C256B-12F1 requirements.
6.How does Aetrix verify that M27C256B-12F1 is sourced from the original manufacturer or authorized distributors?
All M27C256B-12F1 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 M27C256B-12F1 meets industry standards.
7.What is the process for return or replacement of M27C256B-12F1?
All M27C256B-12F1 units undergo pre-shipment inspection (PSI). If there is an issue with M27C256B-12F1, 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 M27C256B-12F1 part is unused and in its original packaging.
Return procedure for M27C256B-12F1:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
M27C256B-12F1 Tags
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