This application note describes the power-down time stamp feature that is available on many STMicroelectronics serial real-time clock (RTC) devices.
This document describes the power-down time stamp feature found in many STMicroelectronics serial Real-Time Clock (RTC) devices. It details how the Halt (HT) bit controls this feature to prevent data corruption during power-up or writes, ensuring that time counters are not overwritten incorrectly.
The guide also covers the importance of using address auto-increment and buffer/transfer registers to ensure coherent reading and writing of date/time values. It provides specific instructions for handling the oscillator stop bit (ST) and outlines a recommended power-up sequence to avoid issues with frozen time data.
Writing to addresses 00h to 07h without first clearing the HT bit will result in the counters being overwritten, thus corrupting the time/date.
No, these specific models do not save the time at power-down; their buffers contain the time of the last access prior to power-down.
Users should always use the address auto-increment feature, which ensures all data is transferred from the same instant in time via buffer registers.