JPS58151622A - Microprocessor - Google Patents

Abstract

PURPOSE:To obtain a microprocessor device which does not generate a problem of external radiation, by multiplying a clock signal applied from the outside of a package, and operating it as an operation clock signal. CONSTITUTION:An output of a crystal oscillating circuit 1 is inputted to a package through a wire 8, and also is inputted to a frequency multiplying circuit 5 through an amplifying circuit 2 and a buffer circuit 3. Oscillation frequency of the circuit 1 is, for instance, 0.5MHz, it is 4-multiplied by the circuit 5, and a clock signal of 2MHz is formed. An output signal 6 raised to necessary frequency by the circuit 5 is inputted to a CPU7, and is used as a clock signal. According to this system, a signal loaded on the wire 8 has comparatively low frequency, and its external radiation quantity is small, but to the CPU7, a clock of necessary frequency is supplied. As for the part operated by low frequency, and input signal 4 of the circuit 5 is inputted directly to the CPU7.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to a microprocessor and its clock signal. In particular, even when installed in a device that handles high-frequency signals, interference caused by external radiation of the clock signal can be avoided. It concerns a microprocessor without generation.

(b) Background of the Technology Microprocessor technology has made remarkable progress in recent years, and devices in many fields are now incorporating microprocessors to improve their functionality.

For example, the image signal processing device of a television receiver may also have a built-in microprocessor for control, but in devices that handle such high-frequency signals, the clock signal to operate the microprocessor is externally transmitted. It may radiate and interfere with the device's original processing functions. That is, in the case of the television receiver, flickering occurs on the screen, and depending on the amount of radiation, it may even fail various standards such as FCC standards.

External radiation of the clock signal is caused by the wiring that connects the crystal oscillator on the printed circuit board and the processor package, which acts as an antenna.The longer the wiring is, the stronger it is, and the higher the oscillation frequency, the stronger the strong.

(c) Prior art and problems The interference caused by the clock signal is reduced as the clock signal is lowered, but the operating speed of the microprocessor also decreases, making it difficult to perform real-time processing such as image signal processing in television reception. If you do so, you will not be able to fulfill that function.

Therefore, currently we use microprocessors that are fast enough to perform the required functions, and the problem of external radiation is suppressed by using external shields such as the chassis or by keeping the wiring as short as possible. This method not only increases the cost of the chassis, but also requires changes to the chassis design and printed circuit board design if the evaluation using test equipment does not apply to the actual product. Problems such as this arise.

(d) Object of the Invention In view of the above circumstances, an object of the present invention is to provide a microprocessor device that operates with a higher clock signal and does not cause the problem of external radiation.

(e) Structure of the Invention In order to achieve the above object, the microprocessor device of the present invention has a circuit that multiplies an externally applied clock signal, and is configured to operate using the output signal of the multiplier circuit as a clock signal. be done.

(f) Embodiment of the Invention FIG. 1 shows the configuration of a microprocessor device of the invention.

The output of the crystal oscillator circuit 1 is input to the package through a wiring 8 as shown in the figure, and is then input to a frequency multiplier circuit 5 via an amplifier circuit 2 and a buffer circuit 3. The oscillation frequency of the crystal oscillation circuit 1 is, for example, 0.degree. 5 MHz, which is multiplied by 4 by the frequency multiplier 5 to form a 2 MHz clock signal.

The output signal 6 increased to the required frequency by the frequency multiplier 5 is input to the CPU 7 and used as a clock signal. If such a system is adopted, the signal on the wiring 8 has a relatively low frequency and the amount of external radiation is small, but the CPU 7 is supplied with a clock signal of the required frequency.

Note that the CPU 7 is not only a CPU but also a ROM.

Those skilled in the art will readily understand that it may also include a RAM or the like. In addition, the input signal of the multiplier circuit 5 is also sent to the CPU as a signal 4 in the part that operates at a low frequency.
It goes without saying that oil must be input into the system.

FIG. 2(a) shows an example in which the frequency multiplier circuit 5 is constituted by an edge detection circuit, and FIG. 2(b) shows its time chart. The waveforms at each point IN, OU1'' and A to E in FIG. 12(a) are shown with the same symbols in FIG. 2(b). In the frequency multiplier circuit, the input IN is multiplied by two at the 0 point, this is further multiplied by two, and the input IN is multiplied by four.

(g) Detailed description of the invention The microprocessor of the present invention uses a relatively low frequency clock signal outside the package, so it has little effect on other devices, and a sufficiently high frequency clock signal inside the package. Since a clock signal is used, the necessary processing speed can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a microprocessor according to the present invention;
FIG. 2 is a diagram showing an example of a frequency multiplier circuit built into the microprocessor. In the figure, 1 is a crystal oscillation circuit, 2 is an amplifier circuit, 3 is a buffer circuit, 5 is a frequency multiplication circuit, 6 is a clock signal which is the output signal of the frequency multiplication circuit, 7 is a CPU, and 8 is wiring for an external clock signal. .

Claims (1)

[Claims] A microprocessor comprising a circuit that multiplies a clock signal applied from outside the package, and operates using an output signal of the multiplier circuit as an operating clock signal.