## Summary of the Provided Text (M48T35/Y Datasheet Excerpt)

This document excerpt details the operation of the STMicroelectronics M48T35/Y non-volatile RAM with integrated timekeeping functionality. Here's a breakdown of the key information:

Core Functionality:

️· Non-Volatile RAM: It acts as standard static RAM when powered, retaining data even when power is removed.
️· Timekeeping: Includes a built-in clock/calendar for real-time tracking.

Key Operational Aspects:

️· Power Failure Protection: Automatically switches to battery power during power loss, preserving both data and clock operation.
️· Clock Reading/Setting: Provides methods to halt clock updates for reading, and to set the clock/calendar with accurate values. Requires specific bit manipulations in a control register (7FF8h).
️· Oscillator Control: The clock oscillator can be stopped to conserve battery life during extended storage. The device ships with the oscillator stopped.
️· Write Protection: During power fluctuations or power loss, the device enters a write-protected state to prevent data corruption.
️· Registers: Uses registers 7FF9h-7FFFh for clock/calendar data and 7FF8h as a control register to manage timekeeping functions.

Important Considerations:

️· Bit Manipulation: Clock reading, setting, and oscillator control all rely on setting/resetting specific bits in the control register.

️· Data Integrity: Potential data corruption during a write cycle occurring during a power failure is mentioned.
️· Battery Life: Extended battery life for data retention (at least 7 years) is a key feature.
️· Application Notes: Refers to Application Notes (AN923 and AN1012) for additional information on century rollover and battery storage life.



In essence, this document provides technical details for developers on how to utilize the M48T35/Y's RAM and timekeeping capabilities effectively while maintaining data integrity and optimizing battery performance.