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STMicroelectronics M27C256B-70C6
- Part No.:
- M27C256B-70C6
- Manufacturer:
- STMicroelectronics
- Category:
- Memory
- Package:
- 32-LCC (J-Lead)
- Datasheet:
-
M27C256B-70C6.pdf
- Description:
- IC EPROM 256KBIT PARALLEL 32PLCC
- Quantity:
- Payment:
- Shipping:
Inventory:3,692
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Product details
Overview
M27C256B-70C6 from STMicroelectronics is a 256 Kbit (32K × 8) UV-erasable EPROM with 5V ±10% supply, 70 ns access time, 30 mA active current, and 100 µA standby current. It features dual-line output control (E/G), electronic signature (20h/8Dh), and supports programming at 12.75 V for 100 µs/word - used in legacy microprocessor boot memory and industrial firmware storage.
For engineers reviewing the M27C256B-70C6 datasheet, M27C256B-70C6 pinout, M27C256B-70C6 application, or M27C256B-70C6 equivalent, key selection criteria include UV-erase capability, TTL-compatible timing, two-level enable architecture (E/G), and FDIP28W/PDIP28/PLCC32/TSOP28 package options across –40°C to +85°C operation.
Technical Context
The M27C256B-70C6 implements a 32K × 8 asynchronous memory array with independent Chip Enable (E) and Output Enable (G) controls, enabling low-power array partitioning and bus contention avoidance. Its read cycle relies on tAVQV = 70 ns (address valid to output valid) under high-speed AC conditions (CL = 30 pF, 1.5 V reference).
Programming requires VPP = 12.75 V ± 0.25 V, VCC = 6.25 V ± 0.25 V, and E-pulsed 95–105 µs width; verify occurs at VPP = 12.75 V with G = VIL and E = VIH. Electronic signature mode activates via 11.5–12.5 V on A9, outputting manufacturer code 20h and device code 8Dh on Q7–Q0.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Memory Size | 256 Kbit (32,768 × 8) - supports full 16-bit address space with byte-wide data interface |
| Access Time | 70 ns - defines maximum clock rate for synchronous read cycles in microprocessor bus interfaces |
| Supply Voltage | 5 V ±10% - compatible with standard TTL/CMOS logic rails without regulation overhead |
| Active Current | 30 mA at 5 MHz - determines decoupling capacitor sizing (0.1 µF ceramic per device) |
| Standby Current | 100 µA - enables low-power retention in battery-backed or intermittent-operation systems |
| Programming Voltage | 12.75 V ±0.25 V - requires dedicated HV supply rail; not compatible with 5 V-only programmers |
| Electronic Signature | Manufacturer Code 20h / Device Code 8Dh - enables automated programmer identification and algorithm selection |
Pinout & Package
Package: PDIP28 (plastic DIP, 600 mil width, temperature range –40°C to +85°C, ordering suffix "C6"). Pin functions validated per Figure 2A (DIP Connections) and Table 1.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| A0–A14 | Address Inputs | 15-bit address bus (32K depth); A9 used for electronic signature voltage injection (11.5–12.5 V) |
| Q0–Q7 | Data Outputs | Bi-directional during programming (data-in), output-only during read; TTL/CMOS compatible |
| E | Chip Enable | Primary device select; CMOS-high places device in 100 µA standby; TTL-low enables memory array |
| G | Output Enable | Secondary output gate; allows shared G-bus across multiple EPROMs while E selects individual devices |
| VPP | Programming Supply | 12.75 V input required only during programming/verify; must be applied simultaneously with or after VCC |
| VCC | Supply Voltage | 5 V ±10% for read; 6.25 V ±0.25 V for programming - mandates separate VCC regulation in HV programming setups |
| VSS | Ground | Reference for all I/O and supply pins; requires low-inductance connection to minimize transient noise |
| NC | No Connect | Internally unconnected pins (e.g., PLCC32 pin 11); must remain floating or grounded per layout guidelines |
Key Features
| Feature | Design Value |
|---|---|
| Dual-line output control (E + G) | Enables hierarchical memory decoding: E selects chip, G gates outputs - eliminates bus contention in multi-chip arrays |
| UV erasability (FDIP28W variant) | Windowed ceramic package allows full bit-pattern reset via 2537 Å UV light (15–20 min @ 12,000 µW/cm²) |
| Electronic signature (20h/8Dh) | Hardware-level device ID read via A9 voltage injection - ensures correct algorithm selection in universal programmers |
| Presto II programming algorithm | Guarantees margin-safe programming in ≤3.5 s via auto-verified 100 µs pulses - no over-programming required |
| –40°C to +85°C operation | Qualified for industrial environments; supports extended thermal cycling in programmable logic controllers and instrumentation |
Applications
| Industrial PLC Firmware Storage | Legacy Microcontroller Boot ROM |
|---|---|
|
Use Scenario: Storing fixed ladder logic and I/O configuration in programmable logic controllers deployed in factory automation cabinets. IC Role / Device Role / Timing Role: Non-volatile boot memory mapped to CPU address space; accessed during power-on reset with 70 ns timing compliance. Use Value: UV-erasable field updates allow firmware revision without PCB replacement; dual E/G control prevents bus conflicts during hot-swap diagnostics. |
Use Scenario: Providing immutable startup code for 8051- and Z80-based embedded controllers in medical analyzers and test equipment. IC Role / Device Role / Timing Role: Read-only instruction memory with TTL-compatible timing; synchronized to system clock via E/G handshaking. Use Value: 100 µA standby current extends battery backup life; electronic signature ensures correct programming algorithm selection during rework. |
| Avionics Maintenance Data Log | Automated Test Equipment (ATE) Pattern Memory |
|
Use Scenario: Retaining calibration constants and fault history in airborne maintenance terminals operating across –40°C to +85°C ambient. IC Role / Device Role / Timing Role: Static configuration store accessed asynchronously during pre-flight self-test sequences. Use Value: Ceramic FDIP28W package withstands thermal shock; UV erasure enables secure data sanitization before equipment redeployment. |
Use Scenario: Holding deterministic test vectors for semiconductor wafer probing systems requiring repeatable stimulus patterns. IC Role / Device Role / Timing Role: High-reliability pattern buffer with precise 70 ns access ensuring sub-cycle timing alignment across parallel channels. Use Value: PRESTO II programming guarantees cell margin integrity across 10⁵+ write cycles; OTP variants (PDIP28/TSOP28) prevent accidental reprogramming. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar EPROM applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AM27C256B-70DC | Same 256 Kbit × 8 organization, 70 ns access, 5 V supply; manufactured by AMD (now Advanced Micro Devices); identical pinout and AC/DC specs | Identical use in microprocessor boot memory; supported by legacy AMD programmer toolchains | Select when sourcing from AMD-dedicated distributors or maintaining AMD-based BOM continuity |
| MX27C256-70PC | 256 Kbit × 8, 70 ns, 5 V; Macronix implementation with minor differences in programming pulse tolerance (±5% vs ±2.5% on VPP) | Suitable for cost-sensitive industrial controls where absolute programming margin is secondary to unit cost | Prefer for new designs targeting lower procurement cost; verify VPP regulation stability in existing programmer hardware |
Compared with M27C256B-70C6, AM27C256B-70DC offers drop-in compatibility and identical qualification, while MX27C256-70PC trades tighter VPP tolerance for cost reduction - both require validation of UV erasure dose and electronic signature response in target programming infrastructure.
Availability
M27C256B-70C6 is available at Aetrix Electronics and suitable for industrial PLC firmware storage, legacy microcontroller boot ROM, avionics maintenance data logging, and automated test equipment pattern memory requiring stable component supply across extended lifecycle programs.
Supply support for M27C256B-70C6 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 broad analog and non-volatile memory portfolios.
The M27C256B belongs to ST's legacy EPROM product line, designed specifically for reliable, field-upgradable firmware storage in microprocessor-based systems where UV erasure or one-time programming meets long-term design stability requirements.
FAQ
What is the minimum UV exposure dose required to fully erase the M27C256B-70C6?
Full erasure requires an integrated UV dose of ≥15 W·sec/cm² at 2537 Å wavelength. Using a standard 12,000 µW/cm² lamp, this corresponds to 15–20 minutes of exposure with the device placed within 2.5 cm of the lamp source. Opaque window covering is mandatory during normal operation to prevent ambient fluorescent-light-induced degradation over years.
Can the M27C256B-70C6 operate with VCC = 5 V during programming?
No. Programming requires VCC = 6.25 V ± 0.25 V and VPP = 12.75 V ± 0.25 V applied simultaneously or with VCC leading. Using 5 V for VCC during programming results in incomplete cell threshold shift and failed verification - the device will not retain programmed data reliably.
Which package types support UV erasure for the M27C256B-70C6?
Only the FDIP28W (ceramic frit-seal with quartz window) package supports UV erasure. The PDIP28, PLCC32, and TSOP28 variants are OTP-only and lack the UV-transparent lid; attempting UV exposure on these packages has no effect and may damage plastic encapsulants.
How does the electronic signature mode function on the M27C256B-70C6?
Electronic signature is activated by applying 11.5–12.5 V to address pin A9 while holding VCC = VPP = 5 V and all other address lines low. Toggling A0 reads manufacturer code 20h (A0 = low) then device code 8Dh (A0 = high) on Q7–Q0 - used exclusively by programmers for automatic algorithm matching.
M27C256B-70C6 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- STMicroelectronics
- Series:
- -
- Package/Case:
- 32-LCC (J-Lead)
- Packaging:
- Tray
- 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:
- 70 ns
- Voltage - Supply:
- 4.5V ~ 5.5V
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 32-PLCC (11.35x13.89)
M27C256B-70C6 FAQ
1.How can I place an order for M27C256B-70C6 through Aetrix?
Please submit a Request for Quotation (RFQ) for M27C256B-70C6 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-70C6 reliable?
The price and inventory of M27C256B-70C6 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for M27C256B-70C6 is usually 5 days.
3.What payment methods are accepted for M27C256B-70C6?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for M27C256B-70C6 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for M27C256B-70C6?
M27C256B-70C6 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your M27C256B-70C6 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-70C6?
For technical support, including M27C256B-70C6 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your M27C256B-70C6 requirements.
6.How does Aetrix verify that M27C256B-70C6 is sourced from the original manufacturer or authorized distributors?
All M27C256B-70C6 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-70C6 meets industry standards.
7.What is the process for return or replacement of M27C256B-70C6?
All M27C256B-70C6 units undergo pre-shipment inspection (PSI). If there is an issue with M27C256B-70C6, 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-70C6 part is unused and in its original packaging.
Return procedure for M27C256B-70C6:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
M27C256B-70C6 Tags
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M24C02-WMN6TP
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AT24C02C-XHM-T
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