JPH03214307A - Clock transmission method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is used in electronic equipment using digital circuits, and relates to a master clock transmission method, and more specifically, to a method for eliminating noise caused by the master clock. This relates to a master clock transmission system.

[Background of the invention and its problems] Conventionally, in this type of clock transmission system, a master clock in the form of a rectangular wave is transmitted directly via a line on the transmitting side, and the master clock is not received on the receiving side. It is meant to be used.

However, if the master clock is transmitted as it is, for example in electronic equipment where digital and analog circuits coexist, the clock noise may be mixed into the analog circuit, and unnecessary radiation due to the high frequency of the clock may become a problem. In particular, there was a problem in that the longer the master clock transmission line, the more it adversely affected the circuit.

This invention was made in view of the above problems, and its purpose is to provide a clock transmission method that eliminates high frequency noise when transmitting a master clock so as not to affect each circuit of the device. .

[Means for Solving the Problems] In order to achieve the above object, the present invention provides the following features when transmitting a master clock of a digital circuit via a line.
On the transmitting side, the master clock is converted into a low-level sine wave and transmitted, and on the receiving side of the master clock, the sine wave is converted into a rectangular wave with a predetermined level and received. .

Further, in the present invention, the transmitting side of the master clock has a bandpass filter that converts the master clock into a sine wave and an attenuator that lowers the level of the sine wave, and the receiving side
It has a resonant circuit that outputs a chronograph using a low-level sine wave.

[Function] With the above method, when transmitting the master clock, on the transmission side, the master clock is converted into a low-level sine wave by the bandpass filter and attenuation section, and this low-level sine wave is transmitted via the line. Transmitted to each circuit. Therefore, generation of unnecessary radiation and high frequency noise due to the high frequency master clock can be prevented, and each circuit, for example, a digital circuit or an analog circuit, will not be adversely affected.

On the other hand, on the receiving side of the master clock, a low level sine wave received via the line generates a clock of a predetermined level.
In other words, a master clock of a level necessary for the circuit (IC circuit) can be obtained by the resonant circuit and the amplifier circuit.

[Example] Hereinafter, an example of the present invention will be described based on FIGS. 1 and 2.

In FIG. 1, an electronic device using digital circuits, analog circuits, etc. includes an oscillation circuit 1 that generates a master clock to be transmitted, a band pass filter (BPF) 2 that converts the master clock into a sine wave, It includes an attenuator 3 that attenuates the sine wave to a low level and outputs the low level sine wave to line L, and a resonant circuit 4 that returns the sine wave via line L to the master clock at a required level. It is being That is, with the line L as a boundary, an oscillation circuit 1, a bandpass filter 2, and an attenuator 3 are provided on the transmitting side of the mask clock, and a resonant circuit 4 is provided on the receiving side, and the resonant circuit 4 outputs the mask clock. The master cross is I
It is designed to be input to a C circuit (IC element).

As shown in the figure, the bandpass filter 2 is composed of, for example, a coil and a capacitor, and the attenuation section 3 is an integrating circuit composed of, for example, a resistor and a capacitor. Further, the resonant circuit 4 is composed of, for example, an LC resonant circuit including a coil and a capacitor, and an amplifier.

Next, the operation of the chronograph transmission system applied to the electronic equipment equipped with the above circuit will be explained based on the time chart diagram of FIG.

First, as shown in FIG. 2A, it is assumed that the oscillation circuit 1 generates a master clock used in each circuit of an electronic device. Then, the master clock is converted into a sine wave by the bandpass filter 2 (see (b) in the same figure).
)), and its level is further lowered by the attenuator 3 (shown in (c) of the same figure). The low-level sine wave is transmitted via line L to each circuit (receiving side).

On the other hand, the resonance circuit 4 on the reception side receives a low-level sine wave via the line L, and outputs a rectangular wave of a predetermined level corresponding to the sine wave to the IC circuit 5 as a master clock (same as above). (shown in figure (d)).

In this way, when transmitting the master clock, a low-level sine wave that does not interfere with other circuits is transmitted via line L, so there is no high-frequency noise that occurs in the past, and it is suitable for analog circuits, for example. There is no possibility of high frequency noise being mixed in, and unnecessary radiation due to the master clover can be prevented.

[Effects of the Invention] As explained above, according to the clock transmission method of the present invention, the master clock transmitting side converts the master clock into a low-level sine wave and outputs it to the line, and the receiving side converts the master clock to a low-level sine wave and outputs it to the line. A rectangular wave of a predetermined level corresponding to the low-level sine wave is input to a predetermined circuit as a master clock, so when transmitting the master clock, unnecessary radiation and generation of high-frequency noise due to the high-frequency master clock can be prevented. This has the effect of preventing adverse effects on each circuit.

[Brief explanation of drawings]

FIG. 1 shows an embodiment of the present invention, a schematic partial block diagram of an electronic device to which the clock transmission method is applied, and FIG.
The figure is a time chart diagram for explaining the operation of the above-mentioned clock transmission system. In the figure, ■ is an oscillation circuit, 2 is a bandpass filter, 3 is an attenuation section,
4 is a resonant circuit, 5 is an IC circuit, and L is a line.

Claims (2)

[Claims] (1) When transmitting the master clock of a digital circuit via a line, the transmitting side converts the master clock into a low-level sine wave and transmits it, and the receiving side of the master clock converts the sine wave into a predetermined sine wave. A clock transmission method characterized by converting the level into a rectangular wave before receiving it. (2) The transmitting side of the master clock has a bandpass filter that converts the master clock into a sine wave and an attenuator that lowers the level of the sine wave, and the receiving side outputs a clock using the low-level sine wave. 2. The clock transmission system according to claim 1, further comprising a resonant circuit that performs a resonant circuit.