JP2963848B2 - Data communication method and apparatus using PWM signal - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data communication using PWM data composed of a plurality of PWM signals, in which a pulse width of a PWM signal is erroneously increased due to a DC component as a signal average value included in the PWM data on a receiving side. The present invention relates to a data communication method and apparatus using a PWM signal that is not detected.

[0002]

2. Description of the Related Art As is well known, the duty ratio of "1" to "0" can be changed according to the signal content during one cycle of a signal of a predetermined frequency. Therefore, when the duty ratio is other than 50%, a DC component as an average value of a signal is included. On the receiving side, generally, a pulse width of a PWM signal is detected by providing a reference voltage between signal levels of "1" and "0".

[0003]

When a DC component is included in the PWM data, the PWM data tends to fluctuate in voltage relative to the reference voltage for detecting the pulse width in accordance with the DC component. In particular, P transmitted through a narrowband transmission path
The voltage fluctuation of the WM data is remarkable. PWM data is "1"
8 having only two values of “1” and “0”, a rectangular waveform as shown by a solid line in FIG.
No error occurs in the detection of "0" and "0". However, PW
The transmission path through which the M data is transmitted contains not only a resistance component but also an inductance component and a capacitance component, and as shown by a broken line in FIG. 8, the PWM data coming into the receiving side rises and falls. The part will be broken. As a result, the duty ratio of the original PWM signal is T ₁ : T ₂ , but if the reference voltage is Sa, the duty ratio is t ₁ a: t ₂ a, and if the reference voltage is Sb, t ₁ b: t ₂ b, and the is detected as a signal of different duty ratios. In particular, in a narrow band transmission line such as a telephone line, since the waveform droop is large,
The effect of the DC component is significant.

[0004] The present invention has been made in view of the above circumstances, and alternately transmits PWM data and an equivalent signal to provide a PWM signal.
An object of the present invention is to provide a data communication method and a device using a PWM signal for transmitting a DC component included in data by canceling the DC component included in an equivalent signal and not including the DC component as a whole. I do.

[0005]

In order to achieve the above object, a data communication method using a PWM signal according to the present invention is to periodically and alternately transmit PWM data composed of a plurality of PWM signals and an equivalent signal. A DC component as a signal average value included in the PWM data is detected, and the equivalent signal is formed of a pulse signal including a DC component having a polarity opposite to the detected DC component and the same magnitude as a signal average value.

A data communication apparatus using a PWM signal according to the present invention comprises: a DC component detecting means for detecting a DC component included in PWM data composed of a plurality of PWM signals; An equivalent signal forming means for forming an equivalent signal with a pulse signal containing the same DC component, and a switching means for periodically and alternately transmitting the PWM data and the equivalent signal corresponding thereto are configured.

The count pulse generator oscillates a count pulse having a cycle shorter than the cycle of the PWM signal, and is switched between up-count and down-count in accordance with the period of “1” and “0” of the PWM signal. The DC component detecting means is formed by a counter for counting the count pulse and an inverting means for switching the output depending on whether or not the count value of the counter is greater than a predetermined value, and the periods of "1" and "0" are different. An equivalent pulse generator that oscillates a pulse signal; and an inversion control unit that outputs the pulse signal as it is or by inverting “1” and “0” according to the output of the inversion unit, and outputs the equivalent signal forming unit. It is formed and formed.

Further, the counter is switched between up-counting and down-counting according to the PWM data during the transmission of the PWM data, and up-counting according to the output of the inversion control means during transmission of the equivalent signal. It can also be configured to switch between and countdown.

The inverting means uses a reset set flip-flop to change the output to "0" when the count value of the counter is "1" or more, and to set the output to "1" when the count value is "0" or less. The inversion control means may be formed by an Ex-OR circuit.

Further, the switching means is formed by switching means controlled by a sequencer, and this switching means is used for transmitting the PWM data while transmitting the PWM data.
M data may be provided to the output terminal and to the counter means, and while transmitting the equivalent signal, the equivalent signal may be provided to the output terminal and to the counter.

[0011]

According to the data communication method and apparatus using a PWM signal according to the first or second aspect, the DC component included in the PWM data is canceled by the DC component included in the equivalent signal, and the PWM data and the equivalent signal are transmitted. Are periodically and alternately transmitted, so that the signal as a whole does not include a DC component. Since this equivalent signal is formed by a pulse signal, it can be transmitted even on a narrow-band transmission line, particularly a transmission line in which low-frequency transmission is difficult to transmit, like the PWM data.

[0012] In the data communication apparatus based on the PWM signal according to the third aspect, the difference between the "1" and "0" periods of the PWM data is detected as a change in the count value of the counter. Then, depending on whether the count value is larger or smaller than a predetermined value, the polarity of the equivalent signal is set so as to cancel the DC component.

Further, in the data communication apparatus based on the PWM signal according to the fourth aspect, while transmitting the equivalent signal,
Since the counter counts up and down by the equivalent signal, the counter is controlled to change the count value in a direction approaching a predetermined value in accordance with the polarity of the equivalent signal for canceling the DC component of the PWM data. Is equal to the predetermined value, it means that the DC component has been canceled. Therefore, the period during which the equivalent signal maintains one polarity to cancel the DC component of the PWM data is appropriately controlled.

According to a fifth aspect of the present invention, in a data communication apparatus using a PWM signal, the output is set to "0" when the count value is "1" or more, and the count value is set to "0" by using a reset / set flip-flop. Since the output is set to "1" below "0", the polarity of the equivalent signal can be set with a simple configuration by the output of the reset set flip-flop.
Since the polarity of the equivalent pulse is directly or inverted by the Ex-OR circuit in accordance with the output of the reset set flip-flop, the configuration for inverting the polarity of the equivalent signal is extremely simple.

Further, in the data communication apparatus using the PWM signal according to the present invention, the period and the period between the transmission of the PWM data and the transmission of the equivalent signal can be easily set by the program of the sequencer by the sequencer and the switch means. Can be set.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a block circuit diagram showing an embodiment of a data communication device using a PWM signal according to the present invention.
FIG. 2 is a diagram showing an example of a signal transmitted from a data communication device using a PWM signal of the present invention, and FIG. 3 is a diagram for explaining the operation of the up / down counter and reset / set flip-flop in FIG. And FIG. 4 shows Ex
FIG. 5 is a diagram for explaining the operation of the -OR circuit, and FIG.
FIG. 9 is a diagram illustrating an equivalent signal after a DC component of data is canceled.

First, the structure of a data communication apparatus using a PWM signal according to the present invention will be described with reference to FIG. Multiple PWM
The input terminal 10 to which signals are sequentially applied is connected to one of the two connection terminals 1a, 2a of the two circuit two-point switch means 12.
a together. The selection contact 1c of one circuit is
The selection contact 2c of the other circuit is connected to the up / down control terminal of the up / down counter 14, and the transmission output terminal 1
6 is connected. The other connecting contacts 1b and 2b are
Both are connected to the output terminal of the Ex-OR circuit 18. The switching of the switch means 12 is controlled by a sequencer 20 in which a program is set in advance.

The clock terminal of the up / down counter 14 is connected to the output terminal of the count pulse oscillator 22.
Further, two terminals from which a signal indicating that the count value of the up / down counter 14 is equal to or more than “1” and equal to or less than “0” are output are a set terminal of the reset set flip-flop 24 and a reset terminal. Connected to terminal. The output terminal of the reset set flip-flop 24 is connected to one input terminal of the Ex-OR circuit 18. The other input terminal of the Ex-OR circuit 18 is connected to the output terminal of the equivalent pulse oscillator 26.

The sequencer 20 connects the selection contacts 1c and 2c of the switch means 12 to the PWM data period for connecting one of the connection contacts 1a and 2a to the other connection contact 1b and 2b.
, And the switching is periodically and alternately controlled with the equivalent signal period connected to. Therefore, during the PWM data period, the PWM data supplied to the input terminal 10 is applied to one of the connection contacts 2a.
The output of the Ex-OR circuit 18 is output from the transmission output terminal 16 via the other connection contact 2b and the selection contact 2c during the equivalent signal period. The equivalent signal period is shorter than the PWM data period, and one line is formed by a pair of the PWM data period and the equivalent signal period. As described later, P
Since an equivalent signal is formed corresponding to the WM data, one line is formed by the preceding PWM data and the subsequent equivalent signal in terms of data transmission, but the synchronization signal period for forming the synchronization of the PWM data is reduced. If it precedes the PWM data, the equivalent signal can be superimposed on the synchronization signal period of the following line. Therefore, the signal transmitted from the transmission output terminal 16 is formed as shown in FIG.

Then, the count pulse oscillator 22
The frequency is set higher than the frequency of the WM signal, for example, several tens times. The up / down counter 14
The WM data is controlled to be up-counted by “1” and down-counted by “0”. Therefore, the PWM shown in FIG.
The count value of the up / down counter 14 changes with respect to the signal as shown in FIG. So, reset and
The set flip-flop 24 has a count value of “1”.
If the count value is equal to or less than "0", the "L" level is output, and if the count value is equal to or less than "0", the "H" level is output as shown in FIG.

The magnitude of the DC component in the PWM data period is indicated by the count value of the up / down counter 14 at the end of the one line PWM data period in FIG. 2, and the equivalent value for canceling this DC component is shown. The polarity of the DC component of the signal is reset / set / flip-flop 24
Is set by the output of

The higher the frequency of the count pulse oscillator 22 is, the more accurately the DC component can be canceled. However, the count value may be increased accordingly, and a large-capacity up-down counter 14 may be used. It becomes necessary and less economical.

Further, the equivalent pulse oscillator 26 has the configuration shown in FIG.
As shown in (a), a pulse whose duty ratio deviates significantly from 50%, for example, a pulse whose duty ratio of "H" to "L" is 1:12 is output. The period is larger than that of the PWM signal, and is set to, for example, 13 times the PWM signal. Then, the Ex-OR circuit 18 outputs the equivalent pulse as it is if the output of the “L” level is given from the reset / set flip-flop 24,
If the “H” level is given, the equivalent pulse is inverted and output. The relationship between the output of the reset set flip-flop 24 and the output of the Ex-OR circuit is shown in FIG.
(B) and (c). The output of the Ex-OR circuit includes a negative DC component when the output of the reset / set flip-flop 24 is at "L" level, and includes "H"
If it is a level, it contains a positive DC component.

As a result, if the preceding PWM data contains a positive DC component, the count value of the up / down counter 14 is "1" or more and the output of the reset / set flip-flop 24 becomes "L". The output of the Ex-OR circuit 18 as a subsequent equivalent signal includes a negative DC component while the equivalent pulse remains as it is, and the positive DC component of the PWM data is canceled. If the preceding PWM data includes a negative DC component, the output of the Ex-OR circuit 18 as an equivalent signal following the preceding PWM data includes a positive DC component in which the equivalent pulse is inverted. Negative DC components will be canceled.

By the way, simply by inverting or inverting the equivalent pulse to obtain an equivalent signal corresponding to the polarity of the DC component included in the PWM data, the magnitude of the DC component of the PWM data and the DC component of the opposite polarity of the equivalent signal are obtained. Do not match. Therefore, in the embodiment, during the period of the equivalent signal, the output of the Ex-OR circuit 18 instead of the PWM data is supplied to the up / down control terminal of the up / down counter 14 by the connection contact 1b of the switch means 12 and the selection contact 1c. Given through. Then, if the count value is “1” or more at the end of the PWM data, the output of the Ex-OR circuit 18 is at “L” level, and the up / down counter 14 is set to down count. Then, each time the count pulse arrives, the count value decreases, and as shown in FIG.
When it reaches "0", the reset / set flip-flop 24 is inverted as shown in FIG.
Then, the output of the Ex-OR circuit 18 is also inverted, and if the equivalent pulse is at the “L” level, it goes to the “H” level. Then, the up / down counter 14 switches to the up count, and the count value becomes “1” by the next incoming count pulse. With this count value “1”, the reset / set flip-flop 24 is again inverted to “L”, and the output of the Ex-OR circuit 18 is also inverted again to “L” level. Therefore, Ex-OR
As shown in FIG. 5, the output of the circuit 18 alternately switches between "H" and "L" for each count pulse, so that no DC component is included.

Therefore, in the equivalent signal, a pulse including a DC component of the opposite polarity is output at the head portion to cancel the DC component included in the PWM data, but when the cancellation is completed, “H” and “L” are output. Are alternately output to change to a pulse containing no DC component. Therefore, the DC component is accurately canceled between the PWM data period and the equivalent signal period.
Note that the product of the magnitude of the DC component as the signal average value of the PWM data and the PWM data period is indicated as the count value of the up / down counter 14. Therefore, the equivalent pulse is set so that the product of the DC component as the average value of the signal of the equivalent pulse and the period until the count value becomes “0” due to the arrival of the count pulse matches the above product of the PWM data. Of course, the duty ratio and the voltage value are appropriately set.

FIG. 6 is a block circuit diagram of another embodiment of a data communication apparatus using a PWM signal according to the present invention. 6, the same reference numerals are given to the same circuit blocks as those in FIG. 1, and duplicate description will be omitted.

The other embodiment shown in FIG. 6 differs from that shown in FIG. 1 in that the absolute value of the count value of the up / down counter 14 at the end of the PWM data is converted into a DC voltage signal. The D / A converter 3 is provided.
0 and the equivalent pulse oscillator 26 in response to the DC voltage signal of Ex.
The gain of the amplifier 32 interposed between the OR circuits 18 is controlled. During the equivalent signal period, the output of the Ex-OR circuit 18 is not supplied to the up / down control terminal of the up / down counter 14, and the up / down counter 14 is cleared by the signal from the sequencer 20 at least at the start of the PWM data. Set to the initial state. And
The gain of the amplifier 32 is controlled such that the DC component included in the PWM data matches the DC component included in the equivalent signal in the entire equivalent signal period.

FIG. 7 is a block circuit diagram of still another embodiment of a data communication apparatus using a PWM signal according to the present invention. 7, the same circuit blocks as those in FIG. 1 are denoted by the same reference numerals, and redundant description will be omitted.

In still another embodiment shown in FIG.
D which converts the count value of the up / down counter 14 after the end of the PWM data into a DC voltage signal including its polarity
A / A converter is provided, and an equivalent pulse output from the equivalent pulse oscillator 26 in response to the DC voltage signal of the D / A converter 40 is subjected to PWM modulation by the PWM modulator 42. Then, this modulated output signal is given to the connection contact 2b of the switch means 12 as an equivalent signal. The DC component included in the equivalent signal output after PWM modulation is represented by PWM
Of course, the modulation is controlled so as to coincide with the DC component included in the M data.

In the embodiment shown in FIGS. 1 and 6, if the up / down counter 14 can be preset to a predetermined value, the reset / set flip-flop 24 outputs the signal in accordance with the predetermined value or more. May be set to switch between “H” and “L”. Also, Ex
Instead of the OR circuit 18, an appropriate circuit that outputs the equivalent pulse as it is or inverted in accordance with the output of the reset / set flip-flop 24 may be used.

The switch means 12 may of course be constituted by an electronic circuit.

[0033]

As described above, since the data communication method using the PWM signal and the apparatus thereof according to the present invention are constituted, the following special effects can be obtained.

In the data communication method and apparatus using the PWM signal according to the first and second aspects, the DC component included in the PWM data is canceled by the DC component included in the equivalent signal, and the DC signal is included in the entire signal. Not. Since this equivalent signal is formed by a pulse signal, P
Like the WM data, it can be transmitted on a narrow band transmission path. Since the PWM data can be transmitted without including a DC component in this manner, when the transmission of the PWM data is started from a no-signal state, the DC component as the average value of the signal changes as in a conventional device of this type. No, ensure that the receiving side
A signal may be received. In particular, the effect is remarkable in a narrow band transmission line such as a telephone line.

In the data communication apparatus using the PWM signal according to the third aspect, the difference between the periods of the PWM data "1" and "0" can be easily detected as the count value of the up / down counter. Then, by setting the polarity of the equivalent signal according to the count value, an equivalent signal including a DC component that cancels the DC component as an average value of the signal included in the PWM data can be easily formed.

Further, in the data communication apparatus based on the PWM signal according to the fourth aspect, since the up-down counter is controlled in accordance with the equivalent signal during the equivalent signal period, the count value is set to the extent that the DC component is canceled. Accordingly, when the count value approaches the predetermined value and the count value matches the predetermined value, it can be determined that the cancellation is completed. Therefore, after the count value reaches the predetermined value, a pulse that does not include a DC component as an average value can be transmitted even within the equivalent signal period.

Further, in the data communication apparatus using the PWM signal according to the fifth aspect, by using the reset set flip-flop and the Ex-OR circuit, the equivalent pulse is directly or inverted according to the count value of the counter. Thus, an equivalent signal including a DC component of a polarity that cancels the DC component of the PWM data can be configured with a simple structure.

Further, in the data communication apparatus using the PWM signal according to the sixth aspect, the switch means for switching between the PWM data period and the equivalent signal period is controlled by the sequencer, so that the period and cycle of each signal are set in advance. It can be easily adjusted by a possible program.

[Brief description of the drawings]

FIG. 1 is a block circuit diagram showing an embodiment of a data communication apparatus using a PWM signal according to the present invention.

FIG. 2 is a diagram illustrating an example of a signal transmitted from a data communication device using a PWM signal according to the present invention.

FIG. 3 is a diagram illustrating the operation of an up / down counter and a reset / set flip-flop in FIG. 1;

FIG. 4 is a diagram illustrating an operation of an Ex-OR circuit.

FIG. 5 is a diagram illustrating an equivalent signal after a DC component of PWM data is canceled.

FIG. 6 is a block circuit diagram of another embodiment of a data communication apparatus using a PWM signal according to the present invention.

FIG. 7 is a block circuit diagram of still another embodiment of a data communication device using a PWM signal according to the present invention.

FIG. 8 is a diagram illustrating that an error occurs in reception of a PWM signal on a receiving side due to fluctuation of a DC component as a signal average value in transmission of PWM data.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Input terminal 12 Switching means 14 Up / down counter 16 Transmission output terminal 18 Ex-OR circuit 20 Sequencer 22 Count pulse oscillator 24 Reset set flip-flop 26 Equivalent pulse oscillator 30, 40 D / A converter 32 Amplifier 42 PWM modulator

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H04L 25/00-25/66

Claims (6)

(57) [Claims] 1. A method of transmitting PWM data comprising a plurality of PWM signals and an equivalent signal periodically and alternately, detecting a DC component as a signal average value included in the PWM data, and detecting the equivalent signal by the detection. A data communication method using a PWM signal, characterized by forming a pulse signal including, as a signal average value, a DC component having the opposite polarity and the same magnitude as the applied DC component. 2. A DC component detecting means for detecting a DC component included in PWM data composed of a plurality of PWM signals, and a pulse signal including a DC component having a polarity opposite to that of the detected DC component and having the same magnitude. A data communication apparatus using a PWM signal, comprising: an equivalent signal forming unit that forms a signal; and a switching unit that periodically and alternately transmits the PWM data and the equivalent signal according to the PWM data. 3. A data communication device using a PWM signal according to claim 2, wherein: a count pulse oscillator oscillating a count pulse having a cycle shorter than a cycle of the PWM signal;
A counter that counts up the count pulse by being switched between up-counting and down-counting in accordance with the period of “1” and “0” of the PWM signal, and outputs an output based on whether the count value of the counter is greater than a predetermined value. An inverting means for switching, the DC component detecting means being formed, an equivalent pulse oscillator for oscillating pulse signals having different periods of "1" and "0", and a pulse signal of "1" according to an output of the inverting means. A data communication device using a PWM signal, characterized in that said equivalent signal forming means is formed by inverting control means for outputting "0" and "0" as they are or by inverting them. 4. The data communication apparatus using a PWM signal according to claim 3, wherein the counter switches between an up-count and a down-count according to the PWM data while transmitting the PWM data, and transmits the equivalent signal. A data communication apparatus based on a PWM signal, wherein the apparatus is configured to switch between up-counting and down-counting in accordance with the output of the inversion control means. 5. The data communication apparatus according to claim 3, wherein the inverting means counts the output to “0” when the count value of the counter is “1” or more by using a reset set flip-flop. PW is characterized in that the output is set to "1" when the value is "0" or less, and the inversion control means is formed by an Ex-OR circuit.
Data communication device using M signal. 6. A data communication apparatus using a PWM signal according to claim 4, wherein said switching means is formed by switching means controlled by a sequencer, and said switching means is configured to transmit said PWM data while transmitting said PWM data. To the output terminal and to the counter means,
A data communication apparatus based on a PWM signal, wherein during transmission of the equivalent signal, the equivalent signal is provided to an output terminal and to the counter.