RV-4162 Datasheet, PDF (19/39 Pages) MICORO CRYSTAL SWITZERLAND – Ultra Small Real Time Clock

Micro Crystal
Ultra Small Real Time Clock / Calendar Module
RV-4162
4.2.2.DEFINING FREQUENCY COMPENSATION VALUE
The simplest method for ascertaining the frequency deviation a given RV-4162 is to measure the frequency
deviation at CLKOUT pin 2. The measured frequency deviation, then, is transformed into an individual
compensation value for this device and programmed into the Frequency Compensation Register (08h).
For test purpose, the following configuration will establish a 32.768 kHz clock at CLKOUT pin 2:
 Bit OS = “0” (bit 7 in register Seconds 01h): enables 32.768 kHz oscillator
 Bits FD3 – FD0 = “0001” (bits 7 - 4 in register Day 04h): select 32.768 kHz CLKOUT frequency
 Bit CLKOE = “1” (bit 6 in register Month Alarm 0Ah): enables CLKOUT pin 2
Please note that this is the default setting at power-up.
The frequency deviation on 32.768000 kHz CLKOUT indicates the degree and direction of time deviation for this
device. A frequency deviation of +0.032768 Hz equals to +1 ppm.
For example, a reading of 32.768650 kHz indicates a frequency deviation of +20 ppm (faster by +1.73 seconds per
day), requiring negative compensation value of “-10d” (xx001010) to be loaded into the Frequency Compensation
Register (08h) for frequency compensation.
It’s important to define the frequency compensation value at an ambient temperature (around 25°C) because of the
crystal’s frequency vs. temperature characteristics shown on page 29.
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