The Voltage Controlled Oscillator block is typically used for modulation applications. The block has a control input signal (orange pin) which specifies a frequency. The blue pin generates a sine tone at the appropriate frequency.
The input value may be from zero to one (5.23 format, or on ADAU145x/ADAU146x, 8.24 format).
The VCO accepts values from 0 Hz (0.0 input) to Fs/2 (1.0 input). Fs is the sampling frequency. The algorithm linearly interpolates the input value into an output frequency.
Note that if the input is greater than 1, the derived output value will fold back to frequencies below Fs/2.