Send an Inquiry

To receive a quote for your project, please fill in the following information, and we’ll get back to you promptly.

Submit Inventory List

Please fill in the following information, and we’ll get back to you promptly.

Home > Products > Integrated Circuits (ICs) > Memory > Memory

STMicroelectronics M27C256B-12C1

Name: M27C256B-12C1
Brand: STMicroelectronics
SKU: M27C256B-12C1
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

Compare

Part No.:: M27C256B-12C1

Manufacturer:: STMicroelectronics

Category:: Memory

Package:: 32-LCC (J-Lead)

Datasheet:: M27C256B-12C1.pdf

Description:: IC EPROM 256KBIT PARALLEL 32PLCC

Quantity:: RFQ Add To RFQ list

Payment:

Shipping:

Inventory:3,123

Please send an inquiry. Send us your inquiry, and we will respond immediately.

Product details

Overview

M27C256B-12C1 from STMicroelectronics is a 256 Kbit (32K × 8) UV-erasable EPROM with 45 ns access time, 5V ±10% supply, and electronic signature support (Manufacturer Code 20h, Device Code 8Dh). It operates in microprocessor memory systems requiring non-volatile program storage, supports two-line output control (E/G), and features FDIP28W ceramic window package for UV erasure.

For engineers reviewing the M27C256B-12C1 datasheet, M27C256B-12C1 pinout, M27C256B-12C1 application, or M27C256B-12C1 equivalent, key selection criteria include UV erasability, 12.75V programming voltage, standby current of 100 µA, and compatibility with TTL-level address/data inputs in legacy embedded memory designs.

Technical Context

The M27C256B-12C1 implements a dual-control read architecture using Chip Enable (E) for power gating and Output Enable (G) for output bus isolation-enabling low-power array operation and eliminating bus contention. Its Electronic Signature mode requires 12V on A9 to read manufacturer and device codes via Q7–Q0.

Programming uses 100 µs pulses at VPP = 12.75V ±0.25V and VCC = 6.25V ±0.25V, with data latched on Q0–Q7 pins during E low pulse; verify occurs at same VPP with G low and E high. Erasure requires 2537 Å UV light at ≥15 W·sec/cm² dose (15–20 min at 12,000 µW/cm²).

Key Specifications

Parameter	Value and Actual Design Meaning
Memory Size	256 Kbit (32,768 × 8), fixed parallel organization for 8-bit microprocessor buses
Access Time	45 ns (tAVQV), enabling direct interface with 10–12 MHz Z80/8086-class CPUs
Supply Voltage	5V ±10% in read mode; 6.25V ±0.25V required during programming
Programming Voltage	VPP = 12.75V ±0.25V applied to dedicated pin, not derived from VCC
Standby Current	100 µA (CMOS E high), reducing system power in idle memory banks
Electronic Signature	Read-only mode with A9 = 12V yields Manufacturer Code 20h and Device Code 8Dh on Q7–Q0
Operating Temp	–40°C to +125°C (Grade 3), validated for industrial and automotive under-hood environments

Pinout & Package

FDIP28W (28-pin ceramic frit-seal DIP with UV-transparent window), 0.6-inch width, 36.8 mm length, 15.2 mm width, 5.7 mm height. Designed for manual UV erasure cycles and socket-based prototyping.

Pin/Terminal	Circuit Role	Design Meaning
A0–A14	Address Inputs	15-bit address bus accepting TTL levels; A9 used as VID select in Electronic Signature mode
Q0–Q7	Data Outputs	Bi-directional I/O pins used for parallel data input during programming and output during read/verify
E	Chip Enable	Active-low primary device select; controls active/standby current states (30 mA / 100 µA)
G	Output Enable	Active-low secondary output gate; enables Hi-Z state independent of E for bus sharing
VPP	Programming Supply	Dedicated 12.75V pin; must be applied simultaneously with or after VCC and removed before or with VCC
VCC	Supply Voltage	5V ±10% for read; 6.25V ±0.25V for programming-separate regulation required
VSS	Ground	Common reference for all signals; decoupling requires 0.1 µF ceramic + 4.7 µF bulk per 8 devices
NC	No Connect	Pins internally unconnected (e.g., PLCC32 pin 16); no external tie required
DU	Don't Use	Reserved internal test node (e.g., PLCC32 pin 32); must remain floating

Key Features

Feature	Design Value
UV Erasability	Full array reset via 2537 Å UV exposure (15–20 min); enables field reprogramming in maintenance workflows
Two-Line Output Control	Independent E (power) and G (output) pins allow hierarchical memory banking without bus contention
Electronic Signature	Hardware-verified device identification (20h/8Dh) for automated programmer compatibility and BOM validation
Low Standby Power	100 µA CMOS standby current reduces quiescent draw in always-on embedded controllers
TTL-Compatible Interface	All address/data pins meet TTL voltage thresholds (VIH = 2V, VOL = 0.4V), simplifying legacy logic interfacing

Applications

Industrial PLC Firmware Storage

Automotive Engine Control Unit (ECU) Boot ROM

Use Scenario: Storing firmware for programmable logic controllers operating in factory-floor environments with wide temperature swings.

IC Role / Device Role / Timing Role: Non-volatile boot memory mapped to CPU address space; accessed during cold start and firmware updates.

Use Value: UV erasability allows field firmware revision without PCB rework; 125°C rating ensures reliability near motor drives and power converters.

Use Scenario: Holding calibration tables and startup routines in engine management systems exposed to under-hood thermal cycling.

IC Role / Device Role / Timing Role: Read-only memory executing critical initialization code prior to RAM initialization and peripheral configuration.

Use Value: –40°C to +125°C operation and 45 ns access time meet ISO 16750-4 thermal stress and real-time boot timing requirements.

Legacy Test Equipment Microcode

Avionics Maintenance Diagnostic Module

Use Scenario: Storing microcode for benchtop oscilloscopes and logic analyzers requiring long-term firmware stability.

IC Role / Device Role / Timing Role: Fixed-function instruction store executed by custom microsequencer; no runtime writes.

Use Value: Ceramic FDIP28W package resists mechanical shock and humidity-induced leakage, ensuring 20+ year data retention.

Use Scenario: Embedded diagnostics in aircraft line-replaceable units (LRUs) needing certified, tamper-resistant firmware storage.

IC Role / Device Role / Timing Role: Secure boot ROM verified via Electronic Signature before loading application code from flash.

Use Value: Manufacturer/device code readout enables anti-counterfeit verification during depot-level maintenance checks.

Equivalent & Alternatives

The following parts are listed as comparable options for similar EPROM applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
AM27C256B-12DC	Same 256 Kbit × 8 organization, 45 ns access, but uses AMD's electronic signature (Manuf. Code 01h)	Requires updated programmer algorithm due to different signature byte sequence	Select only if existing toolchain supports AMD signature; identical pinout and timing enable drop-in replacement
MX27C256-12PC	Macronix variant with 100 µA standby current but no Electronic Signature mode; lacks A9 VID function	Cannot auto-identify in automated programming stations; manual device selection required	Choose when cost sensitivity outweighs signature-driven programming automation needs

Compared with AM27C256B-12DC, M27C256B-12C1 offers ST-specific signature verification for secure toolchain integration; versus MX27C256-12PC, it provides hardware-level device authentication at the cost of slightly higher programming complexity.

Availability

M27C256B-12C1 is available at Aetrix Electronics and suitable for industrial PLC firmware storage, automotive ECU boot ROM, and legacy test equipment microcode requiring stable component supply across extended product lifecycles.

Supply support for M27C256B-12C1 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 over 40 years of non-volatile memory innovation.

The M27C256B belongs to ST's legacy EPROM product line, designed specifically for microprocessor-based systems requiring field-erasable, pin-compatible memory in industrial and automotive applications where long-term data retention and UV reprogrammability are essential.

FAQ

What UV wavelength and exposure time are required to fully erase the M27C256B-12C1?

Full erasure requires short-wave ultraviolet light at 2537 Å wavelength with a minimum integrated dose of 15 W·sec/cm². Using a standard 12,000 µW/cm² UV lamp, the recommended exposure time is 15–20 minutes at a distance of ≤2.5 cm from the lamp tubes. The FDIP28W ceramic window must remain uncovered during exposure.

Can the M27C256B-12C1 be programmed using standard 5V logic levels?

No. Programming requires VPP = 12.75V ±0.25V applied to the dedicated VPP pin and VCC = 6.25V ±0.25V-both voltages exceed standard 5V TTL levels. Address and data inputs remain TTL-compatible (0.8V/2.0V thresholds), but separate high-voltage programming circuitry is mandatory.

How does the Electronic Signature mode work, and what pins are involved?

Electronic Signature mode activates when A9 is driven to 11.5–12.5V (VID) while VCC = VPP = 5V and all other address lines are held low. Toggling A0 between low and high reads Manufacturer Code (20h) and Device Code (8Dh) sequentially on Q7–Q0. This mode operates only at 25°C ±5°C and is used exclusively by programmers for automatic device detection.

Is the M27C256B-12C1 compatible with modern microcontrollers that lack dedicated EPROM control signals?

Yes, but requires external logic translation. The M27C256B-12C1 expects separate E (chip enable) and G (output enable) signals. Modern MCUs with single chip-select outputs must use a simple AND gate or level shifter to generate G from read strobe and E from address decode, preserving the two-line control architecture for correct bus behavior.

M27C256B-12C1 Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: 32-LCC (J-Lead)

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 (TA)

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: 32-PLCC (11.35x13.89)

M27C256B-12C1 FAQ

1.How can I place an order for M27C256B-12C1 through Aetrix?

Please submit a Request for Quotation (RFQ) for M27C256B-12C1 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-12C1 reliable?

The price and inventory of M27C256B-12C1 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for M27C256B-12C1 is usually 5 days.

3.What payment methods are accepted for M27C256B-12C1?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for M27C256B-12C1 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for M27C256B-12C1?

M27C256B-12C1 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your M27C256B-12C1 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-12C1?

For technical support, including M27C256B-12C1 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your M27C256B-12C1 requirements.

6.How does Aetrix verify that M27C256B-12C1 is sourced from the original manufacturer or authorized distributors?

All M27C256B-12C1 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-12C1 meets industry standards.

7.What is the process for return or replacement of M27C256B-12C1?

All M27C256B-12C1 units undergo pre-shipment inspection (PSI). If there is an issue with M27C256B-12C1, 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-12C1 part is unused and in its original packaging.

Return procedure for M27C256B-12C1:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

Tech Hub

2026-09-11 Comparator Circuit: Voltage Thresholds, Op-Amp Differences, LM393 and Practical Design

Comparator circuit design covering voltage thresholds, input limits, open-collector outputs, LM393 wiring, op-amp differences, hysteresis, timing, window detection and practical fault diagnosis.

2026-09-10 Schmitt Trigger Explained: Hysteresis, Circuits, Inverters and Applications

Schmitt triggers use separate rising and falling thresholds to stabilize slow or noisy signals. This guide covers hysteresis, 74HC14 and 74HCT14 selection, comparator calculations, RC oscillators and p…

2026-09-09 Counterfeit Electronic Components: How to Detect, Authenticate, and Test Suspect Parts

Counterfeit components can hide behind convincing markings and passing basic function tests. This engineering reference covers source traceability, external inspection, X-ray, XRF, electrical testing, …

2026-09-08 Obsolete Electronic Components: How to Source and Evaluate Replacements

A practical engineering and sourcing framework covering lifecycle verification, lifetime-buy calculations, replacement qualification, supplier checks and counterfeit-risk controls.

2026-09-07 TTL vs CMOS Logic Levels: 74HC and 74HCT Compatibility Explained

TTL and CMOS logic families differ in thresholds, loading, output drive, power and timing. This engineering guide compares 74HC and 74HCT, calculates noise margins and checks 3.3 V/5 V compatibility.

2026-09-04 Logic Level Shifter: How to Connect 3.3V and 5V Logic Safely

A practical engineering guide to 3.3V and 5V logic compatibility, input thresholds, resistor dividers, translator ICs, MOSFET level shifting, I2C pull-ups, timing limits and power-sequencing risks.

2026-09-03 74HC595 vs TPIC6B595: Output Drive, Pinout, Current, and Load Selection

The 74HC595 uses push-pull logic outputs, while the TPIC6B595 uses 50 V open-drain DMOS sinks for higher-power loads. This guide compares timing, current limits, 3.3 V interfacing, load wiring, thermal…

2026-09-02 74HC595 Pinout, Timing, Output Current, and Applications

The 74HC595 converts serial data into eight stable parallel outputs. This guide covers pin functions, shift and storage timing, OE and MR behavior, drive-current limits, cascading, voltage compatibilit…

2026-09-01 Latch vs Flip-Flop: Timing, Differences and Design Choices

A technical comparison of level-sensitive latches and edge-triggered flip-flops, covering timing windows, setup and hold limits, master–slave operation, time borrowing, race-through, HDL inference and…

2026-08-30 D Latch Circuit: Truth Table, Timing, ICs and Applications

A D latch stores one bit while Enable controls when data can pass. This reference covers gate-level operation, truth tables, transparency, setup and hold timing, LE versus OE, common ICs and practical …