M27C256B-70C6

M27C256B-70C6 is a 256-kbit ultraviolet-erasable EPROM (PROM) in a 28-pin package. It stores firmware and code for microcontrollers in older embedded systems.
Key points:
- Organization: 32K x 8 (A0–A14 address lines; DQ0–DQ7 data outputs)
- Speed/PM: -70 indicates about 70 ns read access time
- Supply and programming: typically Vcc around 5V; a higher programming voltage (Vpp) is required to program; reads occur with /CE and /OE asserted and /WE high
- Erase: UV-erasable through a window; erasing sets memory to all 1s (FFh)
- Pinout basics: A0–A14, DQ0–DQ7, Vcc, GND, Vpp, /CE, /OE, /WE
- Packaging/grade: 28-pin DIP/SOIC; “C6” denotes specific packaging/temperature code
- Use: legacy firmware storage; generally replaced by flash/EEPROM in modern designs
Note: As an older device, it requires a dedicated programmer for initial programming and UV erasure for resets.

Equivalent parts (256 Kibit, 32K×8, 5V, ~70 ns UV-EPROM):
- ST: M27C256B (M27C256B-70)
- Atmel: AT27C256 (AT27C256-15/25)
- AMD: AM27C256 (70 ns)
- Winbond: W27C256 (70 ns)
- Macronix: MX27C256 (70 ns)
Other vendors provide similar 27C256 EPROMs; check cross-reference tables for exact speed/package variants.

M27C256B-70C6 features (concise):
- 256K-bit EPROM: 32K × 8 organization
- Parallel 8‑bit data I/O (D0–D7); 18 address lines (A0–A17)
- 5V operation; Vcc typically 4.5–5.5V
- 12.5V programming supply (Vpp) for programming
- Access time: 70 ns (typical)
- 28‑pin package (C6 code) – DIP/SOP variants
- Control inputs: Chip Enable (CE), Output Enable (OE), and Write/Programming (WE/PGM as applicable)
- Nonvolatile storage with data retained without power; standard PROM behavior
- Suitable for code/storage in microcontrollers and embedded systems
Note: exact I/O timing/voltages can vary by package/temperature grade; consult the specific datasheet for your lot.

- Pin count: 28 pins (28-pin DIP/SSOP variants).
- Function: M27C256B-70C6 is a 256 Kbit UV-erasable EPROM (32K x 8). It provides 8-bit data outputs (D0–D7) addressed by A0–A14, with control inputs CE (active low), OE (active low), and WE (active low); Vcc and Gnd are present. It is read normally, and erased with UV light (programming via a 12.5V process on a programmer). The -70 indicates 70 ns access time.

- Manufacturer: STMicroelectronics (ST)
- What kind of company: A multinational semiconductor and electronics company that designs and manufactures integrated circuits, memory, microcontrollers, sensors, and other ICs for automotive, industrial, and consumer markets.

Applications:
- Firmware storage for 8/16-bit MCUs/MPUs (boot code and program ROM)
- Non-volatile code storage in embedded systems
- Automotive and industrial controllers and instrumentation
- Consumer electronics (set-top boxes, TVs, printers, audio/video devices)
- Prototyping and production boards needing long-term code retention
- Calibration data and lookup tables
Note: M27C256B-70C6 is a 256 Kbit EPROM (32K × 8), 5 V, 70 ns, UV-erasable. It is not typically reprogrammable in-circuit; erasing requires UV exposure. For frequent updates, Flash/EEPROM is preferred.

It’s a 28‑pin ceramic DIP (CERDIP) package, through‑hole.