JPH05315956A - Clock signal generating circuit - Google Patents

Abstract

PURPOSE:To provide a clock signal generating circuit to be used for obtaining a measuring instrument capable of using rapid and synchronizing signals simultaneously with other plural measuring instruments. CONSTITUTION:The clock signal generating circuit to be used for a measuring instrument for measuring an electric signal such as a digital oscilloscope is characteristically provided with a pull-up input terminal 2, an input buffer 3 for amplifying an input signal inputted from the input terminal 2, a crystal oscillation circuit 1 for inputting a signal from the buffer 3 through a coupling capacitor 5, an output buffer 6 for amplifying a signal outputted from the circuit 1, and an output terminal 7 for outputting a signal obtained from the buffer 6 to the external.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a sampling clock signal generation circuit in a digital oscilloscope or the like.

[0002]

2. Description of the Related Art FIG. 1 is a block diagram of a measuring instrument having a conventional sampling clock signal generating circuit. Reference numeral 8 is a measuring device circuit, which is a circuit for measuring a signal. An internal clock generation circuit 11 outputs a sampling clock signal for use in an A / D converter or the like. Specifically, it consists of a crystal oscillator and its peripheral circuits. An external clock input terminal 12 is input when an external signal is used as a sampling clock signal. A switch 13 switches between the signal from the internal clock generating circuit 11 and the signal from the external clock input terminal 12 and outputs the signal to the measuring instrument circuit 8. In such a configuration, whenever a sampling clock signal is required inside the measuring instrument circuit, the signal input from the external clock input terminal 12 and the signal from the internal clock generating circuit 11 are switched each time the sampling clock signal is required. It has to be switched with and used as a clock. Therefore, when trying to input the same clock signal to multiple measuring instruments such as digital oscilloscopes at the same time, prepare an external clock generator and use the same external clock from each clock generator to multiple measuring instruments. It will be input through the input terminal 12.

[0003]

Therefore, signal attenuation occurs when distributing the external clock. Further, since the signal line for connection becomes long, there arises a problem that an accurate operation cannot be performed due to reflection or the like when the frequency of an input signal is high. The object of the present invention is to solve such problems,
It is an object of the present invention to provide a sampling clock signal generation circuit for realizing a measuring instrument capable of simultaneously using high-speed and synchronized sampling clock signals in a plurality of measuring instruments.

[0004]

The present invention provides a pull-up input terminal for inputting a signal from the outside, which is used in a measuring instrument for measuring an electric signal such as a digital oscilloscope, and the input terminal. An input buffer that amplifies the input signal of, and a crystal oscillation circuit that inputs the signal from the input buffer through a coupling capacitor,
An output buffer that amplifies a signal from the crystal oscillator circuit and an output terminal that outputs the signal from the output buffer to the outside are provided, and a clock signal that can be synchronized with a synchronization signal from the outside can be output. It is a characteristic clock signal generating circuit and a circuit provided with a frequency multiplier in the clock signal generating circuit.

[0005]

When the clock signal is generated, the same sampling clock signal can be used simultaneously in a plurality of measuring instruments because the crystal oscillator that starts oscillation by an external input is used.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the basic configuration of the present invention. In the figure, the same parts as those in FIG. Reference numeral 1 is a crystal oscillation circuit, which has the same configuration as the internal clock generation circuit 11 of the conventional example. However, the capacitance of the capacitor 9 in the crystal oscillation circuit 1 is a value obtained by subtracting the capacitance of the capacitor 5 from the value used in the conventional example. Reference numeral 2 is a synchronization input terminal for inputting an external clock. Reference numeral 3 is an input buffer, 4 is a pull-up resistor of the input buffer, and 5 is a coupling capacitor. Reference numeral 6 is an output buffer for amplifying the signal generated in the crystal oscillation circuit 1 so that it can be output to the outside, and reference numeral 7 is a synchronous output terminal. Reference numeral 8 denotes a measuring device circuit that uses the clock signal output from the crystal oscillation circuit 1. The input signal is input from the synchronous input terminal, passes through the input buffer 3 and the coupling capacitor 5, and is input to the crystal oscillation circuit 1. The output of the crystal oscillating circuit 1 is output from the synchronous output terminal after taking the output buffer 6.

First, the operation of the measuring instrument alone will be described. At this time, since nothing is connected to the synchronizing input terminal, the input of the input buffer 3 is fixed to the H level by the pull-up resistor 4. Therefore, the output of the input buffer 3 at this time is 0V. Therefore, the load capacitance of the crystal oscillator becomes the parallel capacitance of the capacitor 9 and the coupling capacitor 5, and the same operation (having the same frequency etc.) as the crystal oscillation circuit in the internal clock generation oscillation circuit 11 in the conventional example is performed. Therefore, the crystal oscillation circuit 1 stably oscillates at a frequency based on the constant of the crystal oscillation circuit 1. When a plurality of measuring instruments are used, that is, when the same sampling clock signal is used by a plurality of measuring instruments, the synchronizing input terminal 2 is provided with the synchronizing output terminal 7 in the sampling clock signal generating circuit in another measuring instrument. Connecting. Therefore, at the input terminal 2 for synchronization,
A signal having a frequency close to the oscillation frequency of the crystal oscillation circuit 1 itself is input. This signal is injected into one side of the crystal oscillator in the crystal oscillation circuit 1 via the input buffer 3 and the coupling capacitor 5. By this injection, the crystal oscillation circuit 1 outputs a signal synchronized with the signal input to the synchronization input terminal 2.

FIG. 2 shows the connection when a plurality of measuring instruments having the sampling clock signal generating circuit according to the present invention are operated in synchronization. The first measuring device serves as a master, and the measuring devices connected thereto are slave 1, slave 2. ． And The synchronization input terminal 2 of the measuring instrument to be the master has nothing, and the signal of the synchronization output terminal 7 of the master is input to the synchronization input terminal 2 of the slave 1. Further, the synchronization output terminal 7 of the strobe 1 is connected to the synchronization input terminal 2 of the strobe 2. In this way, an arbitrary number of measuring instruments are connected.

The operation of the configuration shown in FIG. 2 will be described. Since nothing is connected to the synchronizing input terminal 2 in the clock signal generating circuit in the measuring instrument to be the master, the crystal oscillating circuit 1 in the measuring instrument to be the master oscillates at the frequency. Since the output is input to the slave 1, the clock signal generation circuit in the slave 1 outputs a signal having the same period as the clock output from the master and synchronized with the clock. Since the slave 1 internally uses this clock for sampling, the same sampling clock signal as the master is used. This operation is the same for the slave 2. Since the connection in these is through the buffer, problems such as attenuation or reflection due to distribution are solved.

FIG. 3 is a basic block diagram of a clock signal generation circuit when it is desired to use a frequency higher than the synchronizing signal in each measuring instrument. 1'is a clock generation circuit shown in FIG.
The crystal oscillator circuit 1, the input buffer 3, the pull-up resistor 4 and the coupling capacitor 5 in FIG. Reference numeral 10 is a frequency multiplier. At this time, the signal of the original oscillation which is generated in the clock generation circuit 1 ′ and common to the respective measuring instruments is multiplied by the frequency multiplier 10 and the measuring instrument circuit 8
Used in. Therefore, in such a configuration, the frequency of the synchronized signal is low, and the signal used in the measuring instrument circuit can operate at a high frequency.

[0011]

As described above, according to the present invention, it is possible to realize a measuring instrument in which high-speed and synchronized signals can be simultaneously used in a plurality of measuring instruments by simply connecting the plurality of measuring instruments as they are.

[Brief description of drawings]

FIG. 1 is a basic configuration diagram of the present invention.

FIG. 2 is an example of use of a measuring instrument having the present invention.

FIG. 3 is a basic configuration diagram of a second invention.

FIG. 4 is a basic configuration diagram of a conventional example.

[Explanation of symbols]

 1 Crystal oscillator circuit 2 Synchronous input terminal 3 Input buffer 4 Pull-up resistor 5 Coupling capacitor 6 Output buffer 7 Synchronous output terminal 8 Measurement circuit 9 Capacitor

Claims (2)

[Claims] 1. A pull-up input terminal for inputting an external signal used in a measuring instrument for measuring an electric signal such as a digital oscilloscope, and an input for amplifying an input signal from the input terminal. A buffer, a crystal oscillating circuit that inputs a signal from the input buffer through a coupling capacitor, an output buffer that amplifies the signal from the crystal oscillating circuit, and an output that outputs the signal from the output buffer to the outside. A clock signal generation circuit having a terminal and capable of outputting a clock signal capable of synchronizing with a synchronization signal from the outside. 2. A clock signal generating circuit according to claim 1, further comprising a frequency multiplier for multiplying an output from said crystal oscillator circuit.