JPH03212015A - Waveform shaping circuit using microcomputer - 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 the Invention The present invention relates to a waveform shaping circuit using a microcomputer that clamps an input signal and shapes the waveform.

BACKGROUND OF THE INVENTION FIG. 3 shows a conventional waveform shaping circuit. In FIG. 3, 1 is a clamp circuit, 2 is a waveform shaping circuit, 3 is a clamp voltage generation circuit, 4 is an input terminal, 5 is an output terminal,
6 is a capacitor.

The operation of the conventional waveform shaping circuit configured as described above will be explained below.

Clamp voltage R generated by clamp level generation circuit 3
The input signal P is AC-coupled to the clamp circuit 1 and clamped with P as the clamp level. The clamped signal Q is waveform-shaped by a waveform shaping circuit 2.

The threshold level S of the waveform shaping circuit 2 is created by the clamp voltage generating circuit 3 based on the clamp level.

Further, by switching the threshold voltage S using the output T of the waveform shaping circuit 2, a Schmitt width can be provided. Figure 4 shows the clamp voltage level R and the threshold level S.
(Fig. 4a) and the output T (Fig. 4b). The input signal P is input to the clamp circuit 1 through AC coupling, so that it is clamped below the clamp level R, and at the same time, when it exceeds the threshold level S, the output T of the waveform shaping circuit 2 is output. . By making the waveform vertical while performing clamping, a waveform shaping circuit that is resistant to noise can be realized.

Problems to be Solved by the Invention However, in the conventional configuration described above, the clamp voltage level R is fixed to one type, so the difference between the clamp voltage level R and the threshold level S is small, and the input signal is large. Sometimes sensitive to amplitude modulation. Furthermore, when the difference between the clamp voltage level R and the threshold level S is large, there is a drawback that a sufficient clamping effect cannot be obtained when the level of the input signal is small.

The present invention solves the above conventional problems by switching the clamp voltage level using software.
It is an object of the present invention to provide a waveform shaping circuit using a microcomputer that can stably form a vertical waveform even when the input signal level is high and when the input signal level is low.

Means for Solving the Problems To achieve this object, a waveform shaping circuit using a microcomputer according to the present invention generates a clamp voltage using software using a resistor connected to the microcomputer and a clamp voltage generation circuit using the resistor. It is designed so that it can be switched.

By doing this, when the input signal level is high and the amplitude modulation is large, the software selects the large ramp level (first clamp level), and when the input signal level is small, the small ramp level (first clamp level) is selected. If the clamp level 2) is selected by software, a stable vertical waveform can be obtained in both cases.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a waveform shaping circuit using a microcomputer in one embodiment of the present invention.

In Figure 1, l is a clamp circuit, 2 is a waveform shaping circuit, 4 is an input terminal, 5 is an output terminal, 6 is a capacitor 1
3 is a clamp voltage generation circuit, 14 is a register, and 15 is a data bus.

The operation of the waveform shaping circuit using the microcomputer configured as described above will be explained below. first,
Clamp! by setting a value in register 14 with the microcomputer! A selection is made between the positive level C1 and the clamp voltage level C2.

When input signal A is input from input terminal 4 via AC coupling via capacitor 6, clamp circuit 1 sets input signal A to the selected clamp level C+ or 02.
The following is the clamped signal B. The signal B is input to the waveform shaping circuit 2, and the output E having a vertical waveform is sent to the output terminal 5.
is output from.

FIG. 2 shows the clamp voltage levels C2 and C1 in this embodiment when the input signal A is large and has amplitude modulation.
The waveforms of each part are shown. First, when the clamp voltage level is small and the input amplitude suddenly becomes small, the level of the clamped signal B does not exceed the threshold C2, so the waveform adjustment output E is not output.

For this reason, the waveform adjustment output E is missing several shots (FIG. 2b). It operates normally when the input amplitude changes from small to large.

Next, when the clamp voltage level is high, even if the input amplitude suddenly decreases, the level of the clamped signal B exceeds the threshold C1, so the waveform adjustment output E is output (Figure 2 C). . However, if the amplitude modulation of the input signal is very large, the waveform adjustment output E will be missing at this time as well. By increasing the clamp voltage level, it is possible to form a vertical waveform more stably with respect to amplitude modulation of the input signal.

When the input signal is small (clamp voltage level C2 or higher and clamp voltage level C1 or lower), the closer the clamp voltage level is to the threshold level (that is, the smaller the clamp voltage level is), the stronger the waveform can be shaped into a vertical shape against noise. can.

Effects of the Invention According to the present invention, by setting the clamp voltage level using software, a vertical waveform type with a large clamping effect and a vertical waveform type with a small clamping effect can be selected. The former is effective for a vertical waveform of a signal with a low input signal level and poor S/N ratio. The latter is effective for creating a stable vertical waveform when the input signal level is high and there is amplitude modulation.

[Brief explanation of drawings]

FIG. 3 is a relationship diagram between a pump voltage level and a threshold level. 1... Clamp circuit, 2... Waveform shaping circuit, 3.13... Clamp voltage generation circuit, 4
...Input terminal, 5...Output terminal, 6.
... Capacitor 14 ... Register 15 ... Data bus.

Claims (1)

[Claims] The output of a clamp voltage generation circuit capable of switching the clamp voltage level is connected to the clamp circuit by the output of a register connected to the microcomputer, and the external input signal is clamped by being AC coupled to the clamp circuit with a capacitor. A waveform shaping circuit using a microcomputer, characterized in that the clamped signal is connected to a waveform shaping circuit that is connected to the clamp voltage generation circuit.