STMicroelectronics

M27C256B-90F6

M27C256B-90F6 Description

The M27C256B-90F6 from STMicroelectronics is a 256Kbit (32K x 8) parallel EPROM designed for high-reliability embedded systems requiring non-volatile memory storage. Housed in a 28-pin CDIP (Ceramic Dual In-line Package), this through-hole-mount device operates at a 4.5V–5.5V supply voltage and delivers a 90ns access time, making it suitable for applications demanding fast read operations. Though marked Obsolete, it remains a robust choice for legacy systems due to its ROHS3 compliance and REACH-unaffected status. Its parallel interface ensures straightforward integration with microcontrollers and processors, while the EPROM format allows UV-erasure for reprogramming flexibility.

M27C256B-90F6 Features

• Memory Capacity: 256Kbit organized as 32K x 8 for efficient byte-wide data handling.
• High-Speed Performance: 90ns access time enables rapid data retrieval in time-critical systems.
• Wide Voltage Range: 4.5V–5.5V operation ensures compatibility with standard TTL/CMOS logic levels.
• Durable Packaging: Ceramic DIP (CDIP) offers superior thermal and mechanical stability for harsh environments.
• UV-Erasable: EPROM architecture supports reprogramming after UV exposure, ideal for prototyping and firmware updates.
• Legacy Compliance: ROHS3-compliant and MSL 1 (Unlimited) for unrestricted shelf life and handling.

M27C256B-90F6 Applications

• Industrial Control Systems: Stores firmware for PLCs, motor controllers, and automation equipment where reliability is critical.
• Retro Computing & Legacy Upgrades: Maintains functionality in vintage computers, arcade PCBs, and 8/16-bit systems.
• Embedded Development: Used in prototyping due to its reprogrammability and parallel interface simplicity.
• Telecommunications: Backup memory for base stations and network infrastructure requiring non-volatile storage.
• Automotive Electronics: Suitable for pre-OBD-II diagnostic tools and older engine control units (ECUs).

Conclusion of M27C256B-90F6

The M27C256B-90F6 is a high-performance, UV-erasable EPROM tailored for legacy and industrial applications. Its 90ns access speed, wide voltage tolerance, and rugged CDIP packaging make it a dependable choice despite its obsolete status. While newer flash-based solutions dominate modern designs, this EPROM excels in long-lifecycle systems, repair scenarios, and retro-computing niches. Engineers valuing reprogrammability, parallel interfacing, and proven durability will find it a pragmatic solution for sustaining older hardware.