Introduction
The Real Time Clock (RTC) in Cypress nvSRAM is driven by a crystal oscillator, with an external crystal having a nominal frequency of 32.768 kHz. Most 32.768-kHz crystals have a frequency tolerance of ±20 parts per million (ppm) at +25 °C. This frequency tolerance results in timing error over a long period of time. For example, a crystal with 20-ppm error in nominal frequency can drift the clock accuracy by 52 seconds in a month. You can compensate this drift by using the calibration feature in the nvSRAM RTC.
