Here is the block diagram of a basic synthesiser. The “R-counter” generates the reference frequency. In the MC145152-2 you have about 3 different options. In mine you will have over 2000 different options.
The reference frequency can be interpreted as the channel-spacing of the final synthesiser. The “N-counter” divides the output of the external voltage-controlled oscillator (VCO). The output of the N-counter is compared with the reference frequency, and the different is the error signal that is used to control the VCO.
In principle, the synthesiser is a frequency multiplier. It multiplies a reference frequency by a “N”-counter program.
For example, to synthesise 125kHz you can use a reference frequency of 5kHz and an N-counter program of 25 (25 x 5kHz = 125kHz).
Block diagram of a basic synthesiser
Here is the block diagram of a basic synthesiser. The “R-counter” generates the reference frequency. In the MC145152-2 you have about 3 different options. In mine you will have over 2000 different options.
The reference frequency can be interpreted as the channel-spacing of the final synthesiser. The “N-counter” divides the output of the external voltage-controlled oscillator (VCO). The output of the N-counter is compared with the reference frequency, and the different is the error signal that is used to control the VCO.
In principle, the synthesiser is a frequency multiplier. It multiplies a reference frequency by a “N”-counter program.
For example, to synthesise 125kHz you can use a reference frequency of 5kHz and an N-counter program of 25 (25 x 5kHz = 125kHz).