Multi-mode frequency division circuit
The disclosure provides a multi-mode frequency division circuit including a frequency division factor processor, a frequency divider, and a logic operator. The frequency division factor processor receives the frequency division factor, decomposes the frequency division factor to obtain a first sub-frequency division factor and a second sub-frequency division factor, and outputs the first sub-frequency division factor or the second sub-frequency division factor according to a frequency division clock signal. The divider performs frequency division on the clock signal based on the first sub-frequency division factor or the second sub-frequency division factor to generate the frequency division clock signal. The logic operator sequentially samples the frequency division clock signal according to the rising edge and falling edge of the clock signal to generate a first signal and a second signal, and the logic operator generates an output clock signal according to the first signal, the second signal, and an indication signal.
1. A multi-mode frequency division circuit, comprising:
a frequency division factor processor, receiving a frequency division factor, decomposing the frequency division factor to obtain a first sub-frequency division factor and a second sub-frequency division factor, and selectively outputting the first sub-frequency division factor or the second sub-frequency division factor according to a frequency division clock signal;
a frequency divider, coupled to the frequency division factor processor, receiving a clock signal, performing frequency division on the clock signal based on the first sub-frequency division factor or the second sub-frequency division factor to generate the frequency division clock signal; and
a logic operator, sequentially sampling the frequency division clock signal according to a rising edge and a falling edge of the clock signal to generate a first signal and a second signal, and generating an output clock signal according to the first signal, the second signal, and an indication signal.
2. The multi-mode frequency division circuit according to claim 1 , wherein a duty cycle of the output clock signal is 50%.
3. The multi-mode frequency division circuit according to claim 1 , wherein the frequency division factor processor removes a least significant bit of the frequency division factor to obtain the first sub-frequency division factor, and the first sub-frequency division factor is added to the least significant bit of the frequency division factor to obtain the second sub-frequency division factor.
4. The multi-mode frequency division circuit according to claim 3 , wherein the frequency division factor processor comprises:
a first buffer, configured to store the first sub-frequency division factor;
a second buffer, configured to store the second sub-frequency division factor; and
a multiplexer, coupled to the first buffer and the second buffer, and selectively outputting the first sub-frequency division factor or the second sub-frequency division factor according to the frequency division clock signal.
5. The multi-mode frequency division circuit according to claim 1 , wherein the frequency divider comprises:
a first frequency division device, performing frequency division on the clock signal according to the first sub-frequency division factor or the second sub-frequency division factor to generate a flag signal; and
a second frequency division device, coupled to the first frequency division device, and performing frequency division by two on the flag signal to generate the frequency division clock signal.
6. The multi-mode frequency division circuit according to claim 5 , wherein the first frequency division device comprises:
a prescaler, performing prescaling on the clock signal according to the flag signal to generate a prescaling signal; and
a counter, counting rising edges of the prescaling signal according to the first sub-frequency division factor or the second sub-frequency division factor to generate the flag signal.
7. The multi-mode frequency division circuit according to claim 6 , wherein the prescaler divides a frequency of the clock signal by k in response to the flag signal being logic 0 and divides the frequency of the clock signal by k+1 in response to the flag signal being logic 1, and k is a frequency division factor for prescaling and a positive integer.
8. The multi-mode frequency division circuit according to claim 5 , wherein the second frequency division device is a D-type flip flop.
9. The multi-mode frequency division circuit according to claim 8 , wherein the indication signal is a least significant bit of the frequency division factor.
10. The multi-mode frequency division circuit according to claim 1 , wherein the logic operator comprises:
a first flip flop, sampling the frequency division clock signal according to the rising edge of the clock signal to generate the first signal;
a second flip flop, sampling the first signal according to the falling edge of the clock signal to generate the second signal;
an AND gate, receiving the second signal and the indication signal to generate a third signal; and
an OR gate, receiving the first signal and the third signal to generate the output clock signal.
11. The multi-mode frequency division circuit according to claim 1 , wherein in response to the frequency division factor being an even number, the first sub-frequency division factor and the second sub-frequency division factor are equal, and in response to the frequency division factor being an odd number, a difference between the second sub-frequency division factor and the first sub-frequency division factor is 1.