JPH0293929A - Four value deciding circuit - Google Patents

Abstract

PURPOSE:To simplify a constitution by deciding a four values of a digital input signal based on a 1st output based upon a sine bit expressing the positive/ negative polarity of the digital input signal and a 2nd output based upon a sine bit expressing the positive/negative polarity of an added output between the absolute value of the digital input signal and a threshold signal. CONSTITUTION:A selector 6 outputs the inverse signal of an input signal based upon an inverter 8 when a selection signal utilizing the output of a selector 7 is '1', and when the selection signal is '0', selects an input signal and supplies the selected signal to an adder 9. When the selector 7 selects the sine bit of an input signal supplied to a 1st input terminal 1, the selectors 6, 7, the inverter 8 and the adder 9 form an absolute value circuit, and when input signals supplied to the 1st and 2nd input terminals 1, 2 are respectively defined as X and Y, ¦X¦ + Y is outputted to an output terminal 3. When X, Y < 0, outputs shown by the table are outputted from output terminals 4, 5 and X can be decided by the threshold of '0' and + or -Y. Thus, the constitution of the circuit can be simplified.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a four-value determination circuit, particularly in digital signal processing, which determines the relationship between an input signal and two threshold values having equal 0 and absolute values and different polarities. This invention relates to a four-value determination circuit.

[Conventional technology]

In a digital signal processing system, input signals of four-level code are
A four-value judgment circuit that compares two threshold values having the same absolute value and different polarity is well known.

In this case, there are two typical methods for making a decision by comparing the input signal with a threshold.The first is a method that uses the sign of the result of subtracting the input signal and the decision threshold, and the second is a hardware comparison. This is a method of comparing the two using a device.

The latter method using a hardware comparator is often used to determine multilevel codes in high-speed digital transmission equipment from the viewpoint of processing performance.

FIG. 2 is a block diagram showing an example of a conventional four-value determination circuit used for determining four-value codes.

The four-value judgment circuit in Figure 2 is a hardware comparator 16.1.
7 and a selector 18, and also has a signal input terminal 11.7 that receives an input signal as parallel data. Positive side threshold input terminal 12. The output terminal 15 outputs the sign bit (polarity bit) of the judgment output from the negative threshold input terminal 131, and the output terminal 14 outputs the amplitude information of the output.

In this case, the output expression is a sign bit of “1” or “0” indicating whether the polarity of the input signal is positive or negative, and whether the amplitude exceeds the absolute value of the positive or negative threshold. ″IIZ
This is done by combining the expressions "IIQ".

The selector 18 selectively outputs the output of the comparator 17 when the selection signal is 1, and the output of the comparator 16 when the selection signal is O, and this is supplied to the output terminal 14 as an amplitude output.

Similar to the sign bit of the input signal outputted from the output terminal 15, the selection signal uses the MSB bits 1 and 0 indicating the positive/negative of the input signal of multi-bit parallel data.

Comparators 16 and 17 each compare the input signal as a positive binary number with a positive threshold value and a negative threshold value, and when the threshold value supplied to input terminal A is smaller than the input signal value supplied to input terminal B. outputs this state as A<B is 1, and conversely, when the threshold supplied to input terminal A is greater than or equal to the input signal supplied to input terminal B, outputs this state as A<B. B is expressed as 0, and this 1.0 is supplied to the selector 18, respectively.

Therefore, in general, an input signal representing a negative number in the form of two's complement representation and a threshold value are outputted to the output terminal 15.14 which provides the signal input terminal 11, the positive threshold input terminal 12, and the negative threshold input terminal 13. The sign bit and amplitude information of the determination result are shown as in the determination state diagram in FIG.

[Problem to be solved by the invention]

The conventional four-value determination circuit described above requires two comparators, which has the disadvantage of complicating the circuit scale.

[Means to solve the problem]

The circuit of the present invention is a four-value determination circuit that performs a one-value determination of a digital input signal by comparing it with a threshold signal having an equal number of positive and negative bits. The apparatus further comprises means for performing a four-value determination of the digital input signal based on the output and a second output using a sign bit representing the positive or negative polarity of the addition output of the absolute value of the digital input signal and the threshold signal. be done.

〔Example〕

Next, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a configuration diagram of an embodiment of the four-value determination circuit of the present invention.
A first input terminal 1 for receiving an input signal, a second input terminal for inputting a threshold signal, 2. An output terminal for outputting a 4-value determination result, 3. An output terminal 4 for outputting a sign bit using the MSB bit of the 4-value determination result. , an output terminal 5 that outputs the MSB bit of the input signal, a selector 6.7, an inverter 8, an adder circuit 9
It is composed of:

The selector 6 has a selection signal that uses the output of the selector 7.
”, the inverter 8 outputs an inverted signal of the input signal, and when the selection signal is “0”, the input signal is selected and supplied to the adder 9.

The selector 6.7, the inverter 8 and the adder circuit form an absolute value circuit when the selector 7 selects the sign bit of the input signal supplied to the first input terminal 1; The supplied input signal is connected to X, the second input terminal 2
Let the input signal supplied to output terminal 3 be Y, then l X
Output l +Y.

Here, if the output terminals 4 and 5 are X, Y (<O), the third
The output shown in the figure is obtained, and determination can be made using a threshold value of 0 and ±Y for X. Although this embodiment has been explained using the case where the input signal is parallel data, it is clear that it can be easily implemented even in the case of serial data by first converting it into parallel data. It is also clear that for digital signal processing circuits that also include processing for converting values into values, by using this, the corresponding circuit configuration can be omitted and the required circuit configuration can be further simplified. .

〔Effect of the invention〕

As explained above, according to the present invention, an input signal can be determined in one machine cycle for 0 and two thresholds having the same absolute value and different polarities, and a digital This has the effect of increasing processing capacity in a signal processing device with almost no increase in circuit scale.

the law of nature.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of a four-value determination circuit of the present invention, FIG. 2 is a block diagram showing an example of a four-value determination circuit used for conventional four-value code determination, and FIG. Fig. 1 is a judgment state diagram showing an embodiment of the 4-value judgment circuit expressing the 4-value judgment contents, and Fig. 4 shows the 4-value judgment contents of the conventional 4-value judgment circuit shown in Fig. 3. It is a determination state diagram.

Claims (1)

[Claims] In a four-value judgment circuit that performs four-value judgment of a digital input signal by comparing it with a threshold signal having an equal number of positive and negative bits, It comprises means for performing a four-value determination of the digital input signal based on the output and a second output using a sign bit representing the positive or negative polarity of the addition output of the absolute value of the digital input signal and the threshold signal. A four-value determination circuit characterized by the following.