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STMicroelectronics M27C256B-90F6
- Part No.:
- M27C256B-90F6
- Manufacturer:
- STMicroelectronics
- Category:
- Memory
- Package:
- 28-CDIP (0.600", 15.24mm) Window
- Datasheet:
-
M27C256B-90F6.pdf
- Description:
- IC EPROM 256KBIT PARALLEL 28CDIP
- Quantity:
- Payment:
- Shipping:
Inventory:2,928
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Product details
Overview
M27C256B-90F6 from STMicroelectronics is a 256 Kbit (32K × 8) UV-erasable EPROM in FDIP28W ceramic window package, featuring 90 ns access time, 5V ±10% read supply, and electronic signature (20h/8Dh) for automated programming validation. It serves as nonvolatile program storage in legacy microprocessor systems requiring field-erasable firmware updates via UV exposure.
For engineers reviewing the M27C256B-90F6 datasheet, M27C256B-90F6 pinout, M27C256B-90F6 application, or M27C256B-90F6 equivalent, key selection criteria include UV erasability, dual-line output control (E/G), 12.75V programming voltage, and compatibility with TTL-level address/data buses in embedded controller boot memory designs.
Technical Context
The M27C256B-90F6 implements two independent TTL-compatible control lines-Chip Enable (E) for power gating and Output Enable (G) for output bus arbitration-enabling low-power standby (100 µA) and eliminating bus contention in multi-device memory arrays. Its architecture supports both read and programming modes with separate VCC (6.25V) and VPP (12.75V) supplies.
Electronic signature mode activates at 11.5–12.5V on A9 with VCC = VPP = 5V, allowing host programmers to verify device identity before programming. Erasure requires 15 W·s/cm² UV dose (2537 Å) applied within 2.5 cm of lamp for 15–20 minutes, with room fluorescent light posing multi-year unintentional erasure risk.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory Size | 256 Kbit (32,768 × 8) - fixed parallel organization for byte-wide microprocessor data bus interfacing |
| Access Time | 90 ns - maximum tAVQV delay from address valid to Q-output valid under standard AC conditions (100 pF load) |
| Read Supply | 5V ±10% - single-supply operation compatible with legacy 5V TTL/CMOS systems without level shifting |
| Programming Voltage | 12.75V ±0.25V on VPP - precise high-voltage requirement enabling reliable Fowler-Nordheim tunneling during 100 µs/word write cycles |
| Standby Current | 100 µA - achieved by CMOS-high E input, reducing system power in idle states without external power management |
| Electronic Signature | Manufacturer Code 20h / Device Code 8Dh - read via A9=12V and A0 toggling, enabling auto-algorithm selection in universal programmers |
| Operating Temp | –40°C to 125°C - qualified for industrial and automotive under-hood applications where extended thermal range is mandatory |
Pinout & Package
FDIP28W (28-pin ceramic frit-seal DIP with UV-transparent window) - hermetically sealed package enabling post-deployment firmware erasure using short-wave UV lamps; window diameter ∅7.11 mm, body dimensions 36.9 mm × 15.2 mm × 4.3 mm.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 20–28 | A0–A14, Q0–Q7, VPP, VCC, G, E, VSS | Standard 15-bit address + 8-bit bidirectional data + dual enable + HV programming + power/ground pins per JEDEC DIP layout |
| A0–A14 | Address Inputs | TTL-compatible inputs selecting one of 32,768 memory locations; A9 used for Electronic Signature voltage sensing |
| Q0–Q7 | Data Outputs | Active-low TTL outputs during read; serve as data inputs during programming (latched on E pulse edge) |
| E (Pin 20) | Chip Enable | Primary device select: low enables active/program modes; high forces 100 µA standby with Hi-Z outputs |
| G (Pin 22) | Output Enable | Secondary output gate: low enables Q0–Q7 drivers only when E is also low; prevents bus contention |
| VPP (Pin 1) | Programming Supply | 12.75V input required for programming; internally disconnected during read mode to prevent leakage |
| NC (Pins 18, 19) | Not Connected | No internal connection; must be left floating or tied to ground per layout best practices |
| DU (Pins 16, 17) | Don't Use | Reserved test pins; electrically isolated and not bonded - must remain unconnected |
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 |
| UV erasability (FDIP28W) | Full array erase in 15–20 min using 2537 Å UV lamp at 12000 µW/cm² - supports field firmware rework without device replacement |
| Electronic signature (20h/8Dh) | Hardware-level device ID verification at 12V on A9 eliminates programmer misconfiguration and algorithm mismatches |
| Presto II programming algorithm | Guaranteed margin programming with 100 µs pulses and automatic verify in MARGIN MODE - no overprogramming required |
| Multi-temp grade support | Qualified from –40°C to 125°C (Grade 3) - suitable for engine control units and industrial PLCs without derating |
Applications
| Automotive Engine Control Unit (ECU) | Industrial PLC Firmware Storage |
|---|---|
|
Use Scenario: Storing calibrated fuel injection maps and diagnostic routines in legacy 8051-based ECUs where firmware updates occur infrequently but require field erasure capability. IC Role / Device Role / Timing Role: Nonvolatile boot ROM providing instruction fetch during MCU reset; accessed via 8-bit data bus with 90 ns timing margin for 10 MHz CPU clocks. Use Value: UV window allows recalibration at service centers without soldering; 125°C rating ensures reliability near engine compartments. |
Use Scenario: Holding ladder logic firmware in DIN-rail mounted programmable logic controllers deployed in factory automation environments with ambient temperatures up to 85°C. IC Role / Device Role / Timing Role: Static memory mapped at fixed address space; enabled by decoded E signal and gated by system READ line on G pin. Use Value: Dual-enable architecture prevents bus conflicts during hot-swap I/O module insertion; 100 µA standby current extends backup battery life. |
| Legacy Medical Instrument Boot ROM | Military Communications Radio Firmware |
|
Use Scenario: Storing BIOS and self-test code in Class II medical devices (e.g., infusion pumps) requiring long-term data retention and regulatory traceability. IC Role / Device Role / Timing Role: Read-only memory initialized at power-on; verified via electronic signature before executing safety-critical startup sequence. Use Value: Ceramic FDIP28W package provides hermetic sealing against moisture ingress; 15-year data retention validated per MIL-STD-883. |
Use Scenario: Securing cryptographic key tables and protocol stacks in HF/VHF tactical radios operating in extreme temperature ranges and high-vibration environments. IC Role / Device Role / Timing Role: Memory-mapped configuration store accessed during radio initialization; programmed once pre-deployment with anti-tamper checksums. Use Value: –40°C to 125°C operation ensures functionality in desert or arctic deployments; UV erasure enables secure key revocation in theater. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar EPROM applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AM27C256B-90DC | Same 256 Kbit × 8 organization and 90 ns speed, but uses AMD's proprietary programming algorithm and lacks ST's Presto II margin verification | Requires AMD-specific programmer; no electronic signature compatibility with ST tools | Select only if existing AMD toolchain and firmware infrastructure are in place |
| MX27C256-90PC | Pin-compatible PDIP28 variant with identical AC/DC specs, but rated only to 85°C and lacks UV window (OTP-only) | Cannot be erased or reprogrammed in-field; limited to fixed-function deployments | Choose for cost-sensitive, non-upgradable applications where thermal range ≤85°C suffices |
Compared with AM27C256B-90DC and MX27C256-90PC, the M27C256B-90F6 uniquely combines UV erasability, full industrial temperature range, and ST's verified Presto II programming - making it the only option supporting field firmware revision in harsh environments.
Availability
M27C256B-90F6 is available at Aetrix Electronics and suitable for automotive ECU calibration, industrial PLC firmware storage, legacy medical instrument boot ROM, and military radio configuration memory requiring stable component supply across extended product lifecycles.
Supply support for M27C256B-90F6 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 capabilities.
The M27C256B belongs to ST's legacy EPROM product line designed for high-reliability, long-lifecycle embedded systems where field-upgradable nonvolatile memory remains critical despite flash dominance.
FAQ
What UV wavelength and exposure time are required to fully erase M27C256B-90F6?
Full erasure requires short-wave ultraviolet light at 2537 Å wavelength with a minimum integrated dose of 15 W·s/cm². Using a standard 12000 µW/cm² UV lamp, the device must be placed within 2.5 cm of the lamp for 15–20 minutes. Direct sunlight achieves erasure in ~1 week, while ambient fluorescent lighting may cause partial erasure over 3 years.
Can M27C256B-90F6 be programmed with standard 5V-only programmers?
No. Programming requires a dedicated EPROM programmer capable of supplying 12.75V ±0.25V to the VPP pin while maintaining VCC at 6.25V ±0.25V. Standard 5V-only programmers lack the high-voltage programming circuitry and will fail to alter memory cells, though they may correctly read electronic signature or verify programmed data.
How does the dual enable (E and G) architecture prevent bus contention in multi-chip memory systems?
E controls power state and internal array activation, while G independently gates output drivers. When E is high (standby), outputs are Hi-Z regardless of G state. When multiple devices share a data bus, only the selected chip has E low; all others remain in standby with Hi-Z outputs, eliminating contention even if their G signals are asserted simultaneously.
Is the FDIP28W package RoHS-compliant?
The M27C256B-90F6 predates RoHS legislation (2006) and contains leaded solder in its ceramic frit-seal construction. STMicroelectronics does not offer a RoHS-compliant FDIP28W variant; for compliant alternatives, consider modern SPI NOR flash with software-controlled erase, though UV field erasure capability is lost.
M27C256B-90F6 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:
- 90 ns
- Voltage - Supply:
- 4.5V ~ 5.5V
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 28-CDIP Frit Seal with Window
M27C256B-90F6 FAQ
1.How can I place an order for M27C256B-90F6 through Aetrix?
Please submit a Request for Quotation (RFQ) for M27C256B-90F6 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-90F6 reliable?
The price and inventory of M27C256B-90F6 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for M27C256B-90F6 is usually 5 days.
3.What payment methods are accepted for M27C256B-90F6?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for M27C256B-90F6 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for M27C256B-90F6?
M27C256B-90F6 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your M27C256B-90F6 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-90F6?
For technical support, including M27C256B-90F6 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your M27C256B-90F6 requirements.
6.How does Aetrix verify that M27C256B-90F6 is sourced from the original manufacturer or authorized distributors?
All M27C256B-90F6 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-90F6 meets industry standards.
7.What is the process for return or replacement of M27C256B-90F6?
All M27C256B-90F6 units undergo pre-shipment inspection (PSI). If there is an issue with M27C256B-90F6, 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-90F6 part is unused and in its original packaging.
Return procedure for M27C256B-90F6:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
M27C256B-90F6 Tags
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