This data sheet introduces the features and characteristics of the M41T94 512-bit (64-bit x 8) serial real-time clock (SPI) static random access memory (SRAM).
The M41T94 is a low‑power 512‑bit (64 × 8) Serial RTC‑SRAM with an integrated 32.768 kHz oscillator and battery‑backed time‑keeping functions. It offers 44 bytes of general‑purpose RAM, automatic power‑fail switch‑over, watchdog timer, alarm, and programmable square‑wave output, all accessed via a standard SPI interface.
This manual describes the device’s features, pin assignments, timing diagrams, register maps, and operating procedures. It includes sections on SPI bus characteristics, clock operations, power‑down behavior, alarm configuration, and package mechanical data, as well as revision history and ordering information.
| Memory size | 512 bit (64 × 8) |
|---|---|
| Low operating current | 2.0 mA |
| Battery backup current (max) | 500 nA |
| General‑purpose RAM | 44 bytes |
| Automatic switch‑over circuitry | Yes |
| Power‑down time‑stamp (HT bit) | Supported |
In backup mode the battery supply current is up to 500 nA.
The Chip Enable (E) pin must be low to select the device; when E is high the device is deselected and the SDO pin is high‑impedance.