My Inquiry
My Account
STMicroelectronics M27C256B-45XF1
- Part No.:
- M27C256B-45XF1
- Manufacturer:
- STMicroelectronics
- Category:
- Memory
- Package:
- 28-CDIP (0.600", 15.24mm) Window
- Datasheet:
-
M27C256B-45XF1.pdf
- Description:
- IC EPROM 256KBIT PARALLEL 28CDIP
- Quantity:
- Payment:
- Shipping:
Inventory:1,071
Please send an inquiry. Send us your inquiry, and we will respond immediately.
Product details
Overview
M27C256B-45XF1 from STMicroelectronics is a 256 Kbit (32K × 8) UV-erasable EPROM in FDIP28W ceramic window package, featuring 45 ns access time, 5V ±10% supply, and 12.75V programming voltage. It operates across –40°C to 125°C, supports electronic signature (20h/8Dh), and is used for firmware storage in legacy microprocessor systems requiring non-volatile, field-erasable code retention.
For engineers reviewing the M27C256B-45XF1 datasheet, M27C256B-45XF1 pinout, M27C256B-45XF1 application, or M27C256B-45XF1 equivalent, key selection criteria include UV erasure capability, dual-line control (E/G), TTL-compatible I/O, 100 µA standby current, and FDIP28W package compatibility with UV exposure fixtures.
Technical Context
The M27C256B-45XF1 implements two independent enable controls: Chip Enable (E) for power gating and Output Enable (G) for output bus control-enabling low-power array operation and eliminating bus contention. Its architecture supports parallel 8-bit data I/O with address range A0–A14 and requires VPP = 12.75V ±0.25V only during programming.
Electronic signature mode uses A9 = 11.5–12.5V with A0 toggling to read manufacturer code (20h) and device code (8Dh) on Q7–Q0. Erasure requires 2537 Å UV light at ≥15 W·s/cm² (15–20 min at 12,000 µW/cm² within 2.5 cm of lamp).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory Size | 256 Kbit (32,768 × 8), fixed organization - no bank switching or variable addressing modes. |
| Access Time | 45 ns max (tAVQV/tELQV) at 5V ±10%, 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 - mandates separate VCC regulation for write cycles. |
| Programming Voltage | VPP = 12.75V ±0.25V applied to dedicated pin - requires external high-voltage generator, not derived from VCC. |
| Standby Current | 100 µA (CMOS E-high) - enables low-power hold states in battery-backed or portable embedded systems. |
| Operating Temp | –40°C to +125°C - qualified for industrial/military environments without derating. |
| UV Erase Dose | ≥15 W·s/cm² at 2537 Å - defines minimum lamp intensity × exposure time for full bit reset to '1' state. |
Pinout & Package
FDIP28W (28-pin ceramic frit-seal DIP with UV-transparent window); 0.6-inch width, 1.47-inch length, 0.18-inch height; hermetically sealed with quartz lid for UV erasure.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 20–28 | A0–A14, Q0–Q7, VPP, VCC, VSS, E, G | Standard TTL-level address/data/control I/O; VPP is dedicated high-voltage input, not shared with VCC. |
| A0–A14 | Address Inputs | 15-bit address bus - fully decoded to 32K locations; no partial decoding or internal aliasing. |
| Q0–Q7 | Data Outputs | Bi-directional during programming (data-in), output-only during read - no internal pull-ups or bus-hold. |
| E (Pin 20) | Chip Enable | Active-low primary power control - drives device into 100 µA standby when high; must be decoded per chip in multi-device arrays. |
| G (Pin 22) | Output Enable | Active-low secondary output gate - enables Q0–Q7 only when E is active; allows shared G line across memory banks. |
| VPP (Pin 1) | Programming Supply | 12.75V input exclusively for programming/verify - floating or grounded during read; no internal regulation. |
| A9 (Pin 11) | Electronic Signature Control | 11.5–12.5V input to activate signature mode - not used in normal read/program; requires precise voltage source. |
| NC (Pins 10, 19) | No Connect | Internally unconnected - must remain unconnected; no tie-to-rail or bypass function. |
Key Features
| Feature | Design Value |
|---|---|
| Dual-line output control (E + G) | Enables zero-bus-contention memory expansion - E selects device power state, G gates outputs independently. |
| Electronic signature (20h/8Dh) | Allows automatic device identification by programmers - eliminates manual part selection errors during production programming. |
| UV erasability (FDIP28W) | Supports >100 erase/write cycles with full 2537 Å UV exposure - verified for field reprogramming in maintenance workflows. |
| Presto II programming algorithm | Guarantees margin-safe programming in ≤3.5 s via 100 µs pulses and margin-mode verify - no over-programming required. |
| Wide temperature operation | Specified from –40°C to +125°C - validated for use in automotive engine control units and industrial PLCs without thermal derating. |
Applications
| Industrial PLC Firmware Storage | Legacy Microcontroller Boot ROM |
|---|---|
|
Use Scenario: Storing ladder logic firmware in programmable logic controllers deployed in factory automation cabinets with ambient temperatures up to 70°C. IC Role / Device Role / Timing Role: Non-volatile boot memory mapped to CPU address space; accessed during power-on reset with 45 ns timing compliance. Use Value: UV erasability enables field firmware updates using portable UV erasers; FDIP28W package allows visual verification of window integrity before reprogramming. |
Use Scenario: Holding initialization code for Z80-based medical diagnostic instruments requiring long-term data retention (>10 years) without battery backup. IC Role / Device Role / Timing Role: Read-only memory executing at CPU clock rates up to 12 MHz; E/G control prevents bus conflicts during interrupt servicing. Use Value: 100 µA standby current minimizes system leakage in always-on devices; electronic signature ensures correct algorithm selection during automated test. |
| Military Communications Equipment | Avionics Configuration Memory |
|
Use Scenario: Storing radio protocol stacks in handheld tactical radios operating across –40°C to +85°C environmental chambers. IC Role / Device Role / Timing Role: Firmware storage with guaranteed read timing under extreme thermal cycling; VPP isolation prevents accidental programming during field use. Use Value: –40°C to +125°C rating covers MIL-STD-810H temperature profiles; ceramic FDIP28W package resists mechanical shock and humidity ingress. |
Use Scenario: Holding flight-critical configuration tables in airborne navigation units where rewrite cycles are infrequent but erasure reliability is mandatory. IC Role / Device Role / Timing Role: Secure, tamper-resistant memory with UV window physically sealed after final programming - prevents unauthorized modification. Use Value: 2537 Å UV erasure provides deterministic, repeatable bit reset; electronic signature validates authenticity before loading mission-specific data. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar UV-erasable EPROM applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AM27C256B-45DC | 45 ns access, PDIP28 package, same 256 Kbit × 8 organization and 12.75V VPP - no UV window; OTP-only variant. | Used where field erasure is unnecessary; eliminates UV handling requirements and window sealing steps. | Select when firmware is finalized and permanent retention is required - avoids UV exposure infrastructure and window contamination risks. |
| AT27C256B-45PU | 45 ns access, PDIP28, 5V supply, but uses 21V VPP and different electronic signature codes (1Fh/8Dh); higher programming voltage tolerance. | Suitable for systems with existing 21V programming rails; incompatible with ST's Presto II algorithm and A9-based signature mode. | Choose only if legacy programming hardware already supports 21V VPP and Atmel signature protocols - not drop-in compatible with ST toolchains. |
Compared with AM27C256B-45DC and AT27C256B-45PU, the M27C256B-45XF1 uniquely combines UV erasability, 12.75V VPP, and A9-triggered electronic signature - making it irreplaceable in field-serviceable military and industrial systems requiring verified, reprogrammable firmware storage.
Availability
M27C256B-45XF1 is available at Aetrix Electronics and suitable for industrial PLC firmware storage, legacy microcontroller boot ROM, military communications equipment, and avionics configuration memory requiring stable component supply across extended product lifecycles.
Supply support for M27C256B-45XF1 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, designing and manufacturing analog, MCU, power, and memory products for industrial, automotive, and consumer markets.
The M27C256B belongs to ST's legacy EPROM product line, engineered specifically for high-reliability, field-erasable firmware storage in systems where flash memory was unavailable or unsuitable due to endurance or radiation tolerance requirements.
FAQ
What UV wavelength and exposure dose are required to fully erase the M27C256B-45XF1?
The M27C256B-45XF1 requires short-wave ultraviolet light at 2537 Å with a minimum integrated dose of 15 W·s/cm². Using a standard 12,000 µW/cm² UV lamp, full erasure takes 15–20 minutes with the device placed within 2.5 cm of the lamp tubes. Fluorescent lighting or sunlight may cause partial erasure over months or weeks and must be blocked with opaque labels during storage.
Can the M27C256B-45XF1 be programmed using standard 5V logic levels on all pins except VPP?
Yes - address (A0–A14), data (Q0–Q7), and control inputs (E, G) operate at standard TTL levels (VIL ≤ 0.8V, VIH ≥ 2V) during programming. Only VPP requires 12.75V ±0.25V, and A9 must be driven to 11.5–12.5V only during electronic signature readout. VCC must be set to 6.25V ±0.25V during programming, not 5V.
Is the FDIP28W package of the M27C256B-45XF1 compatible with automated UV erasure equipment?
Yes - the FDIP28W package features a standardized quartz window aligned to JEDEC MO-041 specifications. Its 1.47-inch length and 0.6-inch width match common UV eraser carriers, and the ceramic body withstands repeated 2537 Å exposure without degradation. Window cleanliness must be verified before each erasure cycle to ensure uniform dosage.
How does the two-line control (E and G) prevent bus contention in multi-chip memory systems?
E (Chip Enable) places deselected devices into 100 µA standby with outputs in high-impedance, while G (Output Enable) independently gates outputs of selected devices. This decouples power state from output drive - allowing one G line to serve multiple chips while E lines are individually decoded, eliminating simultaneous drive conflicts on shared data buses.
M27C256B-45XF1 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:
- 45 ns
- Voltage - Supply:
- 4.75V ~ 5.25V
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 28-CDIP Frit Seal with Window
M27C256B-45XF1 FAQ
1.How can I place an order for M27C256B-45XF1 through Aetrix?
Please submit a Request for Quotation (RFQ) for M27C256B-45XF1 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-45XF1 reliable?
The price and inventory of M27C256B-45XF1 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for M27C256B-45XF1 is usually 5 days.
3.What payment methods are accepted for M27C256B-45XF1?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for M27C256B-45XF1 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for M27C256B-45XF1?
M27C256B-45XF1 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your M27C256B-45XF1 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-45XF1?
For technical support, including M27C256B-45XF1 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your M27C256B-45XF1 requirements.
6.How does Aetrix verify that M27C256B-45XF1 is sourced from the original manufacturer or authorized distributors?
All M27C256B-45XF1 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-45XF1 meets industry standards.
7.What is the process for return or replacement of M27C256B-45XF1?
All M27C256B-45XF1 units undergo pre-shipment inspection (PSI). If there is an issue with M27C256B-45XF1, 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-45XF1 part is unused and in its original packaging.
Return procedure for M27C256B-45XF1:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
M27C256B-45XF1 Tags
-
M24C02-WMN6TP
STMicroelectronics
-
AT24C02C-XHM-T
Microchip Technology
-
AT21CS01-STUM10-T
Microchip Technology
-
AT24C02C-SSHM-T
Microchip Technology
-
24LC01BT-I/OT
Microchip Technology
-
M24C02-FMC6TG
STMicroelectronics
-
AT24CS02-SSHM-T
Microchip Technology
-
93LC46BT-I/OT
Microchip Technology
-
AT24C04C-SSHM-T
Microchip Technology
-
24LC01BT-I/SN
Microchip Technology
-
24AA02UIDT-I/OT
Microchip Technology
-
AT24C08C-STUM-T
Microchip Technology
Tech Hub
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, …
A practical engineering and sourcing framework covering lifecycle verification, lifetime-buy calculations, replacement qualification, supplier checks and counterfeit-risk controls.
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.
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.
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…
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…
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…
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 …
An SR latch stores one bit through cross-coupled feedback. This engineering reference covers NOR and NAND implementations, truth tables, forbidden-state recovery, gated operation, switch debouncing, fa…
Latch circuits retain one bit through feedback. This technical reference covers SR and D latches, truth tables, transparency, timing limits, latch-versus-flip-flop behavior, applications and common log…
