Abstract: A clock frequency adjusting method includes the steps of: calculating a phase difference between a local signal and SOF signals or EOP signals in an external signal; counting a count value of the phase difference based on a clock frequency of a local oscillator; and adjusting the clock frequency according to the count value. The present invention further provides a clock frequency adjusting circuit.

Abstract: A differential voltage transmission circuit. The reference bias circuit outputs a first reference voltage, a second reference voltage and a reference current corresponding to a reference current adjusting signal. The differential comparator compares the difference between the first reference voltage and the second reference voltage with the difference between a first output voltage and a second output voltage, and outputs a result signal corresponding to the compared result. The decision circuit outputs the reference current adjusting signal corresponding to the result signal. The output circuit outputs the first output voltage and the second output voltage generated at both terminals of a termination resistor when the reference current flows through the termination resistor.

Abstract: A squelch circuit with an adjustable reference level, having an input level comparator with a first, a second, a third and a fourth current input terminal, a first and a second input terminal, and an output terminal. A first current source is coupled between the first current input terminal and an operation voltage. A second current source is coupled between the second current input terminal and the operation voltage. A third current source is coupled between the third current input terminal and a ground terminal. A fourth current source is coupled between the fourth current input terminal and the ground terminal. A bias generator is coupled to the first, second, third and fourth current sources to generate current control signals thereto according to a reference current and control bits, such that the first, second, third and fourth current sources generate the same current, which adjusts the reference level.

Abstract: A squelch circuit with an adjustable reference level, having an input level comparator with a first, a second, a third and a fourth current input terminal, a first and a second input terminal, and an output terminal. A first current source is coupled between the first current input terminal and an operation voltage. A second current source is coupled between the second current input terminal and the operation voltage. A third current source is coupled between the third current input terminal and a ground terminal. A fourth current source is coupled between the fourth current input terminal and the ground terminal. A bias generator is coupled to the first, second, third and fourth current sources to generate current control signals thereto according to a reference current and control bits, such that the first, second, third and fourth current sources generate the same current, which adjusts the reference level.