JPH11341082A - Transmitter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To transmit/receive data of a low error ratio through an equilibrium transmission line. SOLUTION: The transmitter is provided with a data signal generation means 10 for generating a data signal S to be transmitted, a data compensation signal generation means 11 for generating a data compensation signal for compensating the data signal generated from the means 10, a signal characteristic changing means 12 for changing the duty ratios of the data signal to the data compensation signal in both low and high periods, a transmission means 1 for sending the data signal S0 processed by the means 12 and the data compensation signal to an equilibrium transmission line, a transmission line protection means 3 for protecting a receiving means 2 from a fault generated on the transmission line, the receiving means 2 for receiving and outputting the data signal and the data compensation signal sent through the transmission line, and a signal deterioration detection means 23 for detecting the deterioration information of the data signal S' inputted to the means 21 based on the data compensation signal from the receiving means 2 and feeding back a deterioration information signal to the changing means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission apparatus for exchanging data via a balanced transmission line.

[0002]

2. Description of the Related Art FIG. 5 is a block diagram showing a conventional transmission device. 6A and 6B are diagrams for explaining the operation of a conventional transmission device. FIG. 6A shows a signal waveform to be transmitted, and FIG. 6B shows one differential signal obtained by converting a signal waveform to be transmitted into a differential signal. 6C shows a signal waveform, FIG. 6C shows another differential signal waveform obtained by converting a signal waveform to be transmitted into a differential signal, and FIG. 6D shows a receiving means based on the input differential signal. The output signal waveform to be output is shown. 7A and 7B are explanatory diagrams of the operation of the receiving means in which ideal data transmission / reception is performed. FIG. 7A shows a waveform of a differential signal input to the receiving means, and FIG.
Indicates an output signal waveform output by the receiving means. FIG.
FIG. 3 is a circuit diagram showing a transmission path protection unit and a reception unit. 9A and 9B are explanatory diagrams of the operation of the receiving unit in a state where the balanced transmission line is disconnected. FIG. 9A shows a differential signal waveform input to the receiving unit, and FIG. 3 shows an output signal waveform. FIGS. 10A and 10B are explanatory diagrams of the operation of a receiving unit in which data is actually transmitted and received. FIG. 10A shows a signal waveform to be transmitted, and FIG. FIG. 10C shows a signal waveform output from the receiving means.

[0003] A balanced transmission line has an
It has characteristics that it is resistant to common mode noise, capable of high-speed transmission, capable of long-distance transmission, and easy to connect to a bus, and is widely used.

As shown in FIG. 5, in a transmission device for exchanging data via a balanced transmission line L, when a signal S to be transmitted is input to the transmission means 1, the transmission means 1 S _a, and sent to the balanced transmission line L upon converted to S _b, the receiving means 2 differential signals S _a, the difference in S _b, for receiving a signal S 'that has been transmitted. FIG. 6 shows a specific signal relationship among the signal S to be transmitted, the differential signals S _{a and} S _b , and the transmitted signal S ′.

When a short circuit or disconnection occurs in the balanced transmission line L, the difference value cannot be obtained on the receiving side, so that the signal value cannot be specified. In the worst case, the receiving side device may be damaged. There is. In order to avoid such a situation, as shown in FIG. 8, referred to as fail-safe circuit in front of the receiving means 2, the voltage dividing resistors R _1, ... transmission line protection constituted by R ₄ Means 3 is inserted to avoid the failure of the receiving device.

For example, if the transmission line protection means 3 is not provided, the difference value (S _a -S _b ) becomes 0 when the balanced transmission line L is disconnected.
V, and the transmitted signal S ′ cannot be specified. Normally, as shown in FIG. 7, the receiving means 2 has a high-side threshold H ₀ for signal determination with a zero level Z ₀ interposed therebetween.
And a Low side threshold L _0, the difference value (S _a -S _b) is in the range W of the threshold H ₀ and the threshold value L _0, it can not be identified received signal. However, the provision of the transmission line protection means 3 allows the resistance R to be maintained even when the balanced transmission line L is disconnected.
_1, by the action of R _2, the differential signal S _a of the receiving unit _2, S _b
Is not the zero level Z ₀ , for example, a level H ₁ exceeding the threshold value H ₀ as shown in FIG. 9A, and the output signal of the receiving means 2 as shown in FIG. Hi
gh can be fixed. Of course, it is also possible to fix the output signal of the receiving means 2 to Low.

[0007]

By the way, in the transmission device of the balanced transmission line into which the transmission line protection means 3 is inserted as described above, the differential signals S _{a and} S _{b at} the input of the receiving means 2 are used.
Is normally shifted to the low side or the high side. As a result, the data signal coming through the balanced transmission line L in which the transmission line protection means 3 is inserted is 50% in the high period and 50% in the low period when transmitted from the transmission unit 1.
Even if the data signal has a duty ratio of 50%,
At the time when the signal is received by the receiving means 2, the High period and the Low period are different.

For example, even if a data signal having a duty ratio of 50%, such as a clock signal as shown in FIG.
As shown in the figure, the differential signal as an input of the receiving means 2 is low.
If the deterioration occurs such that the differential signal shifts to the high side, the high period _Th becomes short and the low period _Tl becomes long as shown in FIG. If this occurs, it will be a data signal with a long high period and a short low period (not shown), and the transmission error rate will be higher than in the case of a data signal with the same duty ratio having the same high period and low period as when it occurred. There was a point.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a low transmission error rate and low reliability even when a transmission line protection means is inserted in a balanced transmission line. And to provide an excellent transmission device with high performance.

[0010]

According to the present invention, there is provided a transmission apparatus for transmitting and receiving data via a balanced transmission line, comprising:
Data signal generating means for generating a data signal to be transmitted;
Data compensation signal generation means for generating a data compensation signal for compensating a data signal from the data signal generation means;
Signal characteristic changing means for varying the duty ratio of the data signal and the data compensation signal in the low period and the high period, and transmitting means for transmitting the data signal and the data compensation signal processed by the signal characteristic changing means to the balanced transmission path. Transmission path protection means for protecting the reception means from a failure in the balanced transmission path, reception means for receiving and outputting the data signal and the data compensation signal transmitted via the balanced transmission path, and data from the reception means. Signal deterioration detecting means for detecting deterioration of the data signal inputted to the data processing means based on the compensation signal and feeding back the deterioration information signal to the signal characteristic changing means.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a transmission device according to the present invention will be described below in detail with reference to FIGS.
FIG. 1 is a block diagram showing a transmission device. FIG. 2 is a waveform diagram for explaining the operation of the signal deterioration detecting means when deterioration occurs in which the High period is short and the Low period is long, and FIG.
2B is a clock signal at the time of generation, FIG. 2B is an inverted clock signal at the time of generation, FIG. 2C is a clock signal at the time of reception, and FIG.
2D shows an inverted clock signal at the time of reception, FIG. 2E shows a logical sum signal of the clock signal at the time of reception and the inverted clock signal,
FIG. 2F shows an AND signal of the clock signal and the inverted clock signal at the time of reception. 3A and 3B are waveform diagrams for explaining the operation of the signal deterioration detecting means when the high period is long and the low period is short, and FIG. 3A is a clock signal at the time of occurrence, and FIG. Inverted clock signal of FIG.
3 (c) is a clock signal at the time of reception, FIG. 3 (d) is an inverted clock signal at the time of reception, FIG. 3 (e) is a logical sum signal of the clock signal at the time of reception and the inverted clock signal, and FIG. This is an AND signal of the clock signal and the inverted clock signal at the time of reception. 4A and 4B are timing charts of main signals explaining the operation of the transmission apparatus. FIG. 4A shows a signal waveform to be transmitted, FIG. 4B shows a signal waveform output from the signal characteristic changing unit, and FIG. (C) is a signal waveform at the time of reception. In FIG. 1, the same parts as those of the transmission device described in the related art are denoted by the same reference numerals.

As shown in FIG. 1, the transmission apparatus comprises a transmitting means 1, a data signal generating means 10, a data compensation signal generating means 11, a signal characteristic changing means 12, a balanced transmission line L,
, Receiving means 2, data processing means 21, signal deterioration detecting means 23, and transmission path protecting means 3.

The data signal generating means 10 generates a data signal S to be transmitted and outputs it to the signal characteristic changing means 12. The data compensation signal generating means 11 generates a clock signal CLK, which is a signal having a duty ratio of 50% in a high period of 50% and a low period of 50% corresponding to the data compensation signal, and an inverted clock signal CLK / obtained by inverting the clock signal CLK. , To the signal characteristic changing means 12.

The signal characteristic changing means 12 outputs the data signal S, the clock signal CLK, and the inverted clock signal CLK /
The duty ratios in the High period and the Low period are changed in advance in the direction in which the signal deterioration in the receiving means 2 decreases in accordance with the deterioration information signal output from the signal deterioration detecting means 23, Output.

The transmitting means 1 outputs a data signal S, a clock signal CLK, and an inverted clock signal CLK / which are changed and output in advance by the signal characteristic changing means 12 in accordance with the deterioration information signal.
Are converted into a signal form that can be transmitted to the balanced transmission line L, and then transmitted to the balanced transmission line L.

The balanced transmission line L is composed of a multi-core twisted pair cable or the like. The transmission line protection unit 3 is inserted between the balanced transmission line L and the reception unit 2 to protect the reception unit 2 from failure even if the balanced transmission line L is disconnected for some reason. And, as described in the related art, is usually composed of a voltage dividing resistor.

The receiving means 2 receives the data signal S, the clock signal CLK, and the inverted clock signal CLK / which are transmitted from the transmitting means 1 to the balanced transmission line L and transmitted through the transmission line protecting means 3. The clock signal CLK and the inverted clock signal CLK / in the received signal are converted into a clock signal C which can be processed by the signal deterioration detecting means 23.
LK 'and an inverted clock signal CLK /', which are output to the signal deterioration detecting means 23. The data signal S in the received signal is converted into a data signal S 'which can be processed by the data processing means 21. The data is converted and output to the data processing means 21.

The signal deterioration detecting means 23 outputs the clock signal C
LK ′ and / or inverted clock signal CLK / ′ to detect the tendency and degree of deterioration of the signal, and use the detected deterioration information as a deterioration information signal as signal characteristic changing means 12.
Feedback to The signal deterioration detecting means 23 detects the tendency of signal deterioration and the degree thereof, for example, but not limited thereto, as follows. That is, as shown in FIG. 2 or FIG. 3, the signal deterioration detection unit 23 generates the clock signal CLK ′ and the inverted clock signal CLK ′ based on the clock signal CLK ′ output from the reception unit 2 and the inverted clock signal CLK / ′. OR / CL with CLK / '
K and an AND signal AND-CLK,
The state of the logical sum signal OR-CLK and the logical product signal AND-CLK are monitored.

The signal deterioration detecting means 23 outputs a logical product signal AN
D-CLK is Low as indicated by the straight line L _l in FIG. 2 (f)
If it is fixed to the side, it is determined that the signal degradation tends to have a narrow High period and a wide Low period, and it is determined that the longer the Low period of the OR signal OR-CLK is, the greater the degree of degradation is I do. Further, the signal deterioration detecting means 23
, When the logical sum OR-CLK is fixed to the High side as indicated by the straight line H _h in FIG. 3 (e), wide High period
Based on the determination that the signal degradation tends to be narrow in the Low period, it is determined that the longer the High period of the AND signal AND-CLK is, the more severe the degradation is.

The data processing means 21 converts the data signal S 'which is converted into a processable signal from the receiving means 2 and is output.
Are sequentially determined and read.

That is, in the transmission apparatus described above, even if the signal transmitted through the balanced transmission line L has a narrow high period and a wide low period deterioration,
Even if the gh period is wide and the Low period is short, the signal deterioration detecting means 23 detects the deterioration tendency and the degree of the deterioration, and feeds it back to the signal characteristic changing means 12 as a deterioration information signal.

The signal characteristic changing means 12 knows in advance the tendency of deterioration by the balanced transmission line L and the transmission path protection means 3 and the degree of the deterioration based on the deterioration information signal from the signal deterioration detection means 23, and And the degree of the deterioration in advance, the data signal S output from the data signal generation means 10 and the clock signal CLK and the inverted clock signal CLK / output from the data compensation signal generation means 11 are set in a direction opposite to the deterioration direction. Transmission means 1 after giving the deviation of
Output to

Therefore, for example, the data signal generating means 10
And a data signal S output from the data signal generating means 10 to the signal characteristic changing means 12 and the transmission means 1 receiving the data signal S from the data signal generating means 10 and giving a shift opposite to the tendency of deterioration. a data signal S ₀ to be output to the output the data signal S ₀ and the transmitting means 1 is received from signal characteristics change unit 12, to the balanced transmission line L in terms of converted into the output enable signal form the balanced transmission line L Then, the signal is received by the receiving means 2 via the balanced transmission path L and the transmission path protection means 3, and
Data signal S 'output from to the data processing means 21
The relationship between and is illustrated in FIG.
The data signal S and the data signal S ′ have the same High period and the same Lo period.
A waveform having the same duty ratio having a period can be obtained. Although not shown, the clock signal CLK and the clock signal CL
The same applies to K ′ for the inverted clock signal CLK / and the inverted clock signal CLK / ′.

Therefore, in the transmission device as described above, each of the data signal S, the clock signal CLK, and the inverted clock signal CLK / at the time of reaching the receiving means 2 has a narrow high period and a wide low period. In addition, since the High period is not wide and the Low period is not narrow, and the waveform becomes the same as the waveform at the time of occurrence, highly reliable data transmission and reception with a low transmission error rate can be performed.

[0025]

According to the first aspect of the present invention, the signal deterioration detecting means detects the tendency and the degree of deterioration in the middle of signal transmission based on the transmitted data compensation signal, and determines the detection result. The degradation information signal is fed back to the signal characteristic changing unit, and the signal characteristic modification unit forms a signal waveform that is shifted in advance in reverse to the degradation tendency during signal transmission, based on the degradation information signal that is fed back, The transmitting means sends the signal waveform formed by the signal characteristic changing means based on the deterioration information signal to the receiving means via the balanced transmission path, so that the receiving means always has the same High period as the signal waveform at the time of occurrence. It is possible to receive a signal with the same duty ratio having a low period, and to provide an excellent transmission device capable of transmitting and receiving data with low transmission error rate and high reliability. I do.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a transmission device according to an embodiment of the present invention.

FIG. 2 is a waveform diagram for explaining the operation of the signal deterioration detecting means when the transmission apparatus is deteriorated in which the high period is short and the low period is long.

FIG. 3 is a waveform chart for explaining the operation of the signal deterioration detection means when the transmission device undergoes deterioration in which the high period is long and the low period is short.

FIG. 4 is a timing chart of main signals explaining the operation of the transmission apparatus.

FIG. 5 is a block diagram showing a conventional transmission device.

FIG. 6 is a diagram illustrating the operation of a conventional transmission device.

FIG. 7 is an explanatory diagram of an operation of a receiving unit performing ideal data transfer.

FIG. 8 is a circuit diagram showing a transmission path protection unit and a reception unit.

FIG. 9 is an explanatory diagram of the operation of the receiving means in a state where the balanced transmission line is disconnected.

FIG. 10 is an explanatory diagram of an operation of a receiving unit in which realistic data transmission / reception is performed.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 transmitting means 10 data signal generating means 11 data compensation signal generating means 12 signal characteristic changing means 2 receiving means 21 data processing means 23 signal degradation detecting means 3 transmission path protection means L balanced transmission path S data signal S 'data signal CLK data compensation Signal CLK 'Data compensation signal CLK / Data compensation signal CLK /' Data compensation signal

Claims (1)

[Claims] 1. A transmission apparatus for transmitting and receiving data via a balanced transmission line, comprising: a data signal generating means for generating a data signal to be transmitted; and a data compensation for compensating a data signal from the data signal generating means. A data compensating signal generating means for generating a signal;
Signal characteristic changing means for varying the duty ratio of the low period and the high period, transmitting means for transmitting the data signal and the data compensation signal processed by the signal characteristic changing means to the balanced transmission path, and receiving from the failure of the balanced transmission path Transmission line protection means for protecting the means, reception means for receiving and outputting the data signal and the data compensation signal sent via the balanced transmission path, and data processing means based on the data compensation signal from the reception means And a signal deterioration detecting means for detecting the deterioration of the data signal inputted to the signal characteristic and feeding back the deterioration information signal to the signal characteristic changing means.