M27C256B-12F1
| Parameters | |
|---|---|
| Series | - |
| Moisture Sensitivity Level (MSL) | 1 (Unlimited) |
| RoHS Status | ROHS3 Compliant |
| Package / Case | 28-CDIP (0.600", 15.24mm) Window |
| Mfr | STMicroelectronics |
| Mounting Type | Through Hole |
| Operating Temperature | 0°C ~ 70°C (TA) |
| Technology | EPROM - UV |
| Supplier Device Package | 28-CDIP Frit Seal with Window |
| Access Time | 120 ns |
| Memory Size | 256Kbit |
| Memory Type | Non-Volatile |
| Voltage - Supply | 4.5V ~ 5.5V |
| Memory Organization | 32K x 8 |
| Memory Format | EPROM |
| Memory Interface | Parallel |
| Write Cycle Time - Word, Page | - |
| Package | Tube |
| Product Status | Obsolete |
| Base Product Number | M27C256 |
| REACH Status | REACH Unaffected |
| Standard Package | 13 |
| ECCN | OBSOLETE |
| HTSUS | 8542.32.0061 |
M27C256B-12F1 EPROM - UV Memory IC 256Kbit Parallel 28-CDIP
The M27C256B-12F1 is a STMicroelectronics 256-Kbit (32K x 8) UV-erasable and OTP CMOS EPROM, housed in a 28-FDIP28W ceramic frit-seal DIP with a quartz window for ultraviolet erasure. It is organized as 32,768 bytes of 8 bits each, directly interfacing with standard 8-bit microprocessors through a parallel address and data bus. The -12 speed grade specifies a 120ns maximum access time, while the F1 suffix denotes the windowed ceramic package and commercial 0°C to +70°C temperature range. Operating from a single 5V ± 10% supply in read mode with TTL-compatible inputs, it delivers 30mA active current at 5MHz and just 100µA standby in CMOS mode, making it suitable for low-power legacy embedded systems.
Highlights
● 256-Kbit density organized as 32K x 8 bits, providing 32,768 addressable bytes for firmware, boot code, and lookup tables.
● 120ns maximum access time (-12 speed grade) with 60ns typical output enable time, adequate for 8-bit and early 16-bit microprocessor timing without wait states.
● Single 5V ± 10% read supply (4.5V to 5.5V) with TTL-compatible inputs and CMOS/TTL-compatible outputs, simplifying legacy board power design.
● OTP flexibility: available in PDIP28 and PLCC32 for cost-sensitive final production where erasure is not required.
● Low power: 30mA active at 5MHz, 100µA standby when /CE is high, plus two-line /CE and /OE control to avoid bus contention in larger arrays.
● 12.75V ± 0.25V programming voltage, 100µs/word programming time, PRESTO II algorithm for reliable margin-verified writes across the full array.
FAQ
Q: Is the M27C256B-12F1 recommended for new designs?
A: No, the family is listed as Obsolete; use it only for service, spares, or retro builds. New designs should adopt Flash (e.g., SST39SF010A) or EEPROM alternatives with single-voltage in-system programming.
Q: What usage precautions matter most?
A: Apply VPP = 12.75V ± 0.25V only during programming, keep the UV window covered with an opaque label during normal operation to prevent accidental erasure, and decouple VCC with a 0.1uF ceramic capacitor close to the device.
Alternative Parts
1. M27C256B-12B1 (STMicroelectronics): Same 256Kbit 32K x 8, 120ns EPROM in plastic PDIP-28 OTP package, ideal for cost-sensitive final production without a UV window.
2. M27C256B-10F1 (STMicroelectronics): Identical windowed FDIP28W device with 100ns access speed, offering a pin-compatible performance upgrade when faster timing is required.
3. M27C256B-15F1 (STMicroelectronics): Windowed ceramic 256Kbit EPROM with 150ns access, suitable for slower 8-bit bus designs where the -12 speed grade is over-specified.
4. SST39SF010A-70-4C-PHE (Microchip): 1Mbit CMOS parallel Flash in 32-pin PDIP with 70ns access and 5V single-voltage programming, a modern in-system-reprogrammable replacement for UV EPROM sockets.
