JPH09214566A - Communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely reproduce transmission data which a transmission station transmits on a reception side so as to prevent the deterioration of transmission efficiency even if noise gets into a communication line. SOLUTION: When a reception station receives a transmission frame from the transmission station, an H counter 53 and an L counter 54 respectively count H level pulse/L level pulse width for prescribed pulse cycle quantity. A comparator 55 compares respective count values and detects the difference and the counter of the smaller count value. A transmission part 7 forms a previously equivalent request based on the difference and information on the counter of the smaller count value and outputs it to the transmission station. When the transmission station receives the previously equivalent request, a flag/status detection circuit 52 retrieves status information on the previously equivalent request, and reads a previously equivalent direction and a level which is previously equivalent. The transmission part 7 forms transmission data obtained by changing the duty ratio of the waveform of transmission data based on the information and transmits it to the reception station.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication system for transmitting by cable, and more particularly to a communication system for transmitting transmission data in which waveform distortion of transmission data is pre-equivalent.

[0002]

2. Description of the Related Art Conventionally, a programmable controller and
For example, a method is generally adopted in which input / output devices such as a sensor, a switch, and a relay are connected by a wire cable, digital / analog conversion is performed on transmission data, and serial communication is performed.

However, in such a wired communication system for transmitting data, due to intersymbol interference due to group delay characteristics and attenuation characteristics, for example, a waveform of transmission data output from a transmitting station is shown in FIG. 15 (a). If the waveform is
The waveform received by the receiving station after the transmission data is converted into analog is distorted as shown in FIG.

Therefore, when the receiving station restores the transmission data from this distorted waveform to a digital signal, the restored transmission data is a pulse of the transmission data transmitted by the transmitting station, as shown in FIG. 15 (c). There is a problem that the transmission data cannot be accurately reproduced because the width may be wider or narrower than the width.

As described above, the reception station cannot accurately reproduce the transmission data due to the distortion of the waveform due to the inter-symbol interference, and further, the reception station has the threshold level higher than 0V as shown in FIG. 15 (d). , The recovered transmission data due to the waveform distorted due to intersymbol interference has a high pulse rise / fall level. Therefore, as shown in FIG. Further, there is a problem that the H level width of the pulse is constantly narrowed and the transmission data cannot be reproduced more accurately.

Therefore, as one of the solutions to such a problem, conventionally, the transmission distortion amount between the transmitting station and the receiving station is measured in advance before the communication system starts up, and this measurement is performed. Based on the amount of distortion, the waveform of the original transmission data is corrected in advance so that the transmission data is almost the same as the original transmission data at the reception station, and the original transmission data is transmitted to the reception station. That is, the pre-equivalence processing of the transmission data is being performed.

[0007]

However, as described above, in the communication system in which the transmission data is pre-equalized in advance in consideration of the waveform distortion due to the intersymbol interference and the difference in the threshold level, noise is introduced into the communication line. In this case, the waveform of the corrected transmission data causes noise and intersymbol interference, the waveform of the corrected transmission data is distorted, and as a result, the receiving station cannot reproduce accurate transmission data. there were.

Therefore, the receiving station has a problem that the transmission data is judged to be erroneous by the FCS check inspection or the like, and a request for retransmitting data is frequently made until the noise is removed, resulting in a decrease in transmission efficiency. It was

In view of the above problems, the present invention accurately reproduces the transmission data transmitted by the transmitting station on the receiving station side even when noise enters the communication line, and as a result, communication in which the transmission efficiency is not deteriorated. The purpose is to provide a system.

[0010]

In order to achieve the above object, the invention according to claim 1 preliminarily equalizes a transmission waveform of a transmission frame by a transmission station in consideration of a transmission waveform distortion when transmitting a wired line. And a communication system for transmitting to a receiving station,
The transmitting station comprises a changing means for changing the duty ratio of the transmitting frame, and the receiving station measures the waveform distortion amount of the transmitting frame received from the transmitting station, and the measuring means. Only when the measured distortion amount of the transmission frame waveform is within a predetermined range, there is a judgment means, and when the distortion amount of the transmission frame waveform is not within the predetermined range by this judgment means, the duplication of the transmission frame is performed. −
And a pre-equivalence request means for transmitting a pre-equalization request for changing the Tee ratio to the transmitting station.

A second aspect of the invention is characterized in that, in the first aspect of the invention, the transmission frame is a Manchester code.

According to a third aspect of the present invention, in the first aspect of the present invention, a transmission frame having Manchester code and a duty ratio of 50% until the transmission station receives a pre-equivalence request from the reception station. Is transmitted to the receiving station.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the pre-equivalence request has information indicating a pre-equivalent direction and information indicating a pre-equivalent amount for the pre-equivalent direction. It is characterized by

According to a fifth aspect of the invention, in the invention of the fourth aspect, the information indicating the pre-equivalent direction widens the width of either the H level waveform or the L level waveform. And the information indicating the pre-equivalent amount is an amount that widens the width of the waveform.

A sixth aspect of the present invention is characterized in that, in the fifth aspect of the invention, the pre-equivalent amount is a system clock frequency unit.

According to a seventh aspect of the invention, in the first aspect of the invention, the transmitting station and the receiving station have the same system clock frequency.

The invention described in claim 8 is characterized in that, in the invention described in claim 1, the measuring means measures waveform distortion with a transmission waveform indicated by status information of the transmission frame.

According to a ninth aspect of the present invention, in the first aspect of the present invention, the measuring means sets the H level pulse width and the L level pulse width in a predetermined pulse cycle in the transmission frame to the system clock. The number of outputs is converted, and the amount of distortion of the transmission frame waveform is measured by the difference between the number of outputs of the system clock of the H level pulse and the number of outputs of the system clock of the L level pulse obtained by the conversion.

The invention described in claim 10 is characterized in that, in the invention described in claim 9, the predetermined pulse cycle is a pulse cycle indicated by status information of the transmission frame.

According to an eleventh aspect of the present invention, in the first aspect of the present invention, the pre-equivalence requesting means determines the duty cycle of the transmission frame according to the distortion amount of the pulse waveform of the transmission data.
It is characterized in that the pre-equivalence request with different changes in the tee ratio is transmitted to the transmitting station.

According to a twelfth aspect of the present invention, in the invention according to the first aspect, a pre-equivalent transmission frame is sent to the receiving station only when the transmitting station receives a pre-equivalence request from the receiving station a predetermined number of times. It is characterized by transmitting.

According to a thirteenth aspect of the present invention, in a communication system having a relationship between a master station and a slave station and having a polling selecting system, the master station automatically performs polling preequivalent processing on the slave station. It is characterized by transmitting.

According to a fourteenth aspect of the present invention, in the thirteenth aspect of the present invention, the pre-equalization-processed polling is transmitted when the master station is turned on.

According to the present invention, the receiving station measures the amount of distortion of the transmission frame waveform received from the transmitting station and issues a pre-equalization request to the transmitting station to change the duty ratio of the transmitting frame when necessary. Send. Then, the transmitting station transmits the transmission data whose duty ratio has been changed in advance to the receiving station based on the pre-equivalence request from the receiving station, so that the receiving station can reduce the influence of the waveform generated during the transmission.

Further, according to the present invention, in the communication system of the polling selecting system, the master station automatically transmits the pre-equivalent polling to the slave station.
It becomes easy to judge whether the line is defective due to noise on the line or the line is defective due to the failure of the device itself.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a communication system according to the present invention will be described below with reference to the drawings.

<First Embodiment> FIG. 1 is a block diagram showing the arrangement of a communication system according to the first embodiment.

The communication system of this embodiment includes a transmitting station 1.
And a receiving station 2 are connected via a cable 3 to transmit a transmission frame composed of a Manchester code, and when transmitting the transmission frame, a transmission frame pre-equivalent in consideration of waveform distortion is preliminarily considered. It is a communication system that transmits to the receiving station 2.

Further, in this communication system, the transmitting station 1 and the receiving station 2 have the same system clock frequency.

Here, the Manchester code conversion is shown in FIG.
As shown in, H (High) level is first set to L (Low) level in the pulse waveform forming the transmission frame before conversion to Manchester code, and then converted to H level at a predetermined location, usually the center, as a boundary. Also, it means that the L level of the transmission frame before conversion to Manchester code is first set to H level and then converted to L level.

Therefore, when converting the transmission frame to Manchester code, if the boundary between the H level and the L level is set at the center of the pulse, the transmission code converted to Manchester code always has a duty ratio of 50%.

Incidentally, as shown in FIG. 3, "H, H,
When the pulse waveform of the transmission frame at the L, L, H "level is converted into Manchester code," L, H, L,
A pulse waveform having H, H, LH, L, L, and H ″ levels is obtained.

Next, the structure of the transmission frame transmitted between the transmission station 1 and the reception station 2 will be described with reference to FIG.

This transmission frame 90 includes transmission data for transmitting original data, a transmission request for transmission from the transmission station 1 to the reception station 2, a transmission response for transmission to the transmission station in response to this transmission request, and There is a type of retransmission request to be transmitted to the transmitting station 1. These are as shown in the figure.
A start flag area 91 in which a flag indicating the start of a frame is stored, and a status area 9 in which status information indicating the type and transmission state of a transmission frame is stored
2, a node address area 93 in which a source node address and a destination node address are stored, and a transmission data area 94 in which original transmission data is stored.
And a FCS (Fram Check Seqen) that stores a cyclic code for performing a CRC (Cyclic Redundancy Check) check.
ce) area 95 and an end flag area 96 in which a flag indicating the end of the frame is stored.

The status area 92 has a size of 1 byte and has the following information.

Information indicating the type of the transmission frame is stored in bits 0, 1, and 2. If "(0,0,0)" is stored, it indicates that the transmission frame is transmission data, and if "(0,0,1)" is stored, preequivalence is performed. It indicates that it is a request, and that it is a transmission request in the case of “(0,1,0)”, and it is a transmission response in the case of “(0,1,1)”. It means that there is “(1,0,0)
In the case of ", a resend request is shown.

Bit 3 has information indicating the amount of data that can be handled. When "0" is stored, it indicates that 4-bit data can be processed, and when "1" is stored, 8-bit data can be processed.

Bit 4 has information about the presence / absence of a pre-equivalence request. When it is "0", it indicates that there is no pre-equivalence request, and when it is "1", there is a pre-equivalence request. It is shown that.

Bit 5 has information indicating the direction of pre-equivalence, and when it is "0", the width of the H-level pulse waveform is widened (hereinafter referred to as pre-equivalence in the H-level direction). In the case of “1”, it means that the width of the L-level pulse waveform is widened (hereinafter, referred to as pre-equivalence in the L-level direction).

Bit 6 and bit 7 are reserved as spares.

FIG. 5 is a block diagram showing the configuration of the transmitting station 1 and the receiving station 2.

In a general communication system, a station connected to a wired line acts as a transmitting station at some times and as a receiving station at other times, so that the transmitting station 1 and the receiving station of this embodiment are used. The station 2 has the same configuration as shown in FIG.

The transmitting station 1 and the receiving station 2 perform a process of receiving transmission data and a transmission request from the transmitting station 1 and measuring the amount of distortion of the waveform when the station itself works as the receiving station 2. When the own station functions as the transmitting station 1, the receiving unit 5 that performs processing such as interpreting the content of the pre-equivalence request transmitted from the receiving station 2, and the main control that controls the receiving unit 5 and the transmitting unit 7 The unit 6 sends a pre-equivalence request, a transmission response, and a resend request to the transmitting station 1 when the own station acts as the receiving station 2, and transmits the transmission data and the transmission request when the own station acts as the transmitting station 1. The receiver 6 is provided with a transmitter 6 for transmitting.

Here, the receiving unit 5 detects the digital filter 51 for removing the noise of the transmission frame such as the transmission data transmitted from the transmitting station, the flag and the status contents, and when the flag is detected, the H counter is detected. The flag / status detection circuit 52 for activating the 53 and the L counter 54, and H for measuring the width of the H level pulse and the L level pulse in the pulse waveform indicating the status information of the transmission frame by the count value of the number of outputs of the system clock.
The counter 53 and the L counter 54 are compared with the count values counted by the H counter 53 and the L counter 54,
If the difference is outside the predetermined range, the counter with the smaller count and the comparator 55 that outputs the count difference and the flag when the flag information is received from the digital filter 51 are sampled, that is, the bits of the transmitted transmission frame. A synchronous clock required for specifying the position is generated, and this clock is received by the reception buffer 57,
The FCS check circuit 58 and the synchronization control circuit 56 for outputting to the reception control unit 59, the reception buffer 57 for sampling the reception data based on the synchronization clock and temporarily storing the data, and the FCS area 94 in the reception data 90. It is composed of an FCS check circuit 58 for detecting an error in the received data using the cyclic code and a reception control unit 59 for controlling the receiving unit 5 as a whole.

The main controller 6 controls the receiver 5 and the transmitter 7 described later.

The transmission unit 7 outputs transmission data, a pre-equivalence request and a retransmission request in accordance with an instruction from the main control unit 6, and a transmission control unit 71 for generating a data selector switching timing, which will be described later, a flag, and a status. , A data selector 72 that generates a transmission frame such as transmission data in the order of data and FCS, an FCS generation circuit 73 that generates a cyclic code for performing a CRC check, and a Manchester encoding circuit 74 that converts the transmission frame into a Manchester code. And a pre-equivalent circuit 75 for converting the waveform of the transmission frame into a predetermined duty ratio.

Here, the above-mentioned H counter 53 and L
The count value measured by the counter 54 will be further described with reference to FIG.

While the receiving station 2 is in operation, as shown in FIG.
It becomes the standard for the processing operation timing of the station itself, and the system clock with a unique frequency is always output.
The transmitted transmission frame is received, and thereafter, the H counter 53 and the L counter 54 make the flag detection circuit 52.
When activated by, the H counter 53 and the L counter 54 respectively indicate the above-mentioned status information stored in the status area 92, that is, the width and L level pulse indicated by the H level pulse in the pulse waveform of 1 byte. Is measured as the number of system clock outputs.

Incidentally, at the H level in FIG.
Counting is required, and 10 counts are required at the H level in the figure. Also, L in
The level requires 8 counts, and the H level in the figure requires 6 counts.

Next, as shown in FIG. 7, in the transmitting station 1, the transmission data transmitted to the receiving station 2 (see in the figure) has a waveform distortion outside a predetermined range, and the receiving station 2 transmits to the transmitting station. After outputting the pre-equivalence request for 1 (see the figure), the transmitting station 1
Will be described in detail with reference to the flowcharts of FIGS. 8 and 9 based on the pre-equivalence request.

(1) Processing until the receiving station 2 receiving the transmission data sends a pre-equivalence request to the transmitting station 1 The transmitting station 1 transmits the transmitting data to the receiving station 2 and receives the transmitting data. The digital filter 51 of the receiving station 2 that has been removed removes noise from the transmission data and removes it from the reception buffer 57.
And output to the flag / status detection circuit 52 (step 810).

When the flag / status detection circuit 52 detects the flag indicating the beginning of the transmission data from which noise has been removed, the H-counter 53 and the L counter 54 are activated, and the contents of the status are checked and sent. It is detected that the received frame is transmission data (step 820).

H counter 53 and L activated
The counter 54 counts the number of outputs of the system clock for the width of the H level pulse and the L level pulse of the pulse waveform indicating the status information in the transmission frame, and outputs the count value to the comparator 55 (step 830). .

The comparator 55 compares the count values counted by the H counter 53 and the L counter 54,
It is detected whether or not the difference is outside the predetermined range (step 8).
40) If the difference is outside the predetermined range (step 840; Y), the counter with the smaller count value and the count difference are stored in a memory (not shown) (step 850), while the difference is predetermined. If it is within the range (step 840; N), the process of transmitting the pre-equivalence request to the transmitting station 1 is terminated.

During the above-described processing, the synchronizing circuit 56 that receives the flag information from the digital filter 51 generates the synchronizing clock necessary for sampling, and supplies this to the receiving buffer 57. The signal is output to the reception control unit 59, and the reception buffer 57 samples the command frame output from the digital filter 51 based on the synchronous clock, and temporarily stores this.

The FCS check circuit 58 also receives the FCS of the received data 90 output from the digital filter 51.
CR by referring to the cyclic code stored in area 94
C check is performed to check the transmission data for errors.

The reception controller 59 determines whether or not the transmission data has been received (step 860). That is, when the reception control unit 59 receives the information indicating that the end flag of the transmission data is detected from the flag / status detection circuit 52, the reception control unit 59 determines that the reception of the transmission data is completed, and the information indicating that the end flag is detected. It is determined that the transmission data has not been received until the request is not received.

When the reception control unit 59 determines that the transmission data has been received (step 860; Y), it activates the main control unit 6, while it determines that the transmission data has not been received. (Step 860; N),
The state is maintained until the reception of the transmission data is completed.

Then, the main control section 6 gives an instruction to the transmission control section 71 of the transmission section 7 to transmit a pre-equivalence request to the transmission station 1, and also information necessary for the pre-equivalence request, for example, the transmission station 1. Node address, the node address of the own station 2, the direction of pre-equivalence, etc. (hereinafter referred to as pre-equivalence information) are output to the transmitter 7 (step 870).

Here, as the node address of the transmitting station 1 and the node address of its own station, the information of the transmission data temporarily stored in the receiving buffer 57 is used, and the direction of pre-equivalence is determined by the receiving control unit 59. Received comparator 55
The counter with the smaller count value is used.

Receiving the pre-equivalence information, the transmitting unit 7 creates a pre-equivalence request as follows and transmits it to the transmitting station 1 (step 880).

That is, when the transmission control unit 71 of the transmission unit 7 receives an instruction from the main control unit 6 to transmit a pre-equivalence request, it instructs the data selector 71 to create a pre-equivalence request.

Then, the data selector 71
The status having the pre-equivalent direction, the node address, and the FCS are formed in this order, and are sequentially output to the Manchester encoding circuit 74.

Here, the pre-equivalence request start flag area 9
1 contains the same flags as transmission data and resend request, and bit 0,
Information 1 (1
0,1) "is information indicating that there is a pre-equivalence request in bit 4, and information indicating a pre-equivalence direction is in bit 5.
For example, if the ruling party is in the H level direction, "0" is entered. The node address area 93 stores the node address of the transmitting station 1 that receives the pre-equivalence request and the node address of the local station 2 that has transmitted the pre-equivalence request. The data area 94 is empty. FCS
The area 95 contains the CRC cyclic code generated by the FCS generating circuit, and the end flag area 96 contains the same flags as the transmission data and the retransmission request.

The Manchester encoding circuit 74 converts the start flag, the status having the pre-equivalent direction, the node address, the FCS and the end flag, which are sequentially formed, into a Manchester code and outputs it to the pre-equivalence circuit 75.

The pre-equivalent circuit 75 transmits the formed pre-equivalent request to the transmitting station 1 based on the instruction of the transmission control unit 71 without converting the duty ratio.

(2) Processing in which the transmitting station 1 that has received the pre-equivalence request transmits to the pre-equivalent transmission data receiving station When the transmitting station 1 receives the pre-equivalence request from the receiving station 2, the digital filter 51 The requested noise is removed, and this is output to the reception buffer 57 and the flag / status detection circuit 52 (step 910).

When the flag / status detection circuit 52 detects the flag indicating the beginning of the pre-equivalence request from which noise has been removed, the flag / status detection circuit 52 activates the H-counter 53, the L counter 54, and the reception control section 59, and the H-counter 53 and L-counter 53. Counter 5
The count of 4 is incremented (step 920).

After that, the flag / status detection circuit 52
Checks the contents of the status, and when it detects that the sent one is a pre-equivalence request, it stops counting up the H counter 53 and the L counter 54 and clears this count value to 0 (step 93
0).

Here, the reason why the counting of the H counter 53 and the L counter 54 is stopped to be incremented and the count value is cleared to 0 is that the process currently being performed depends on the pre-equivalence request from the receiving station 2. This is because it is necessary to perform a process of outputting a command frame having a predetermined duty ratio, and it is not necessary to make a pre-equivalence request to the receiving station 2.

The flag / status detection circuit 52 further checks the contents of the status, detects the pre-equivalent direction from the information contained in bit 5 in the status area 92, and latches it in a register (not shown) (step 940). .

During the above-described processing, the synchronizing circuit 56 which receives the flag information from the digital filter 51 generates the synchronizing clock necessary for sampling, and uses this as the receiving buffer 57. Output to the reception control unit 59, the reception buffer 57 samples the pre-equivalence request output from the digital filter 51 based on the synchronous clock, and temporarily stores this.

Further, the FCS check circuit 58 outputs the FCS of the pre-equivalence request 90 output from the digital filter 51.
CR by referring to the cyclic code stored in area 94
C inspection is performed to check data for errors.

The reception control unit 59 determines whether the pre-equivalence request has been received (step 950). That is, when the reception control unit 59 receives information indicating that the end flag of the pre-equivalence request is detected from the flag / status detection circuit 52, the reception control unit 59 determines that the transmission data is completely received, while the reception control unit 59 indicates that the end flag is detected. It is determined that the pre-equivalence request has not been received until the information is received.

When the reception control unit 59 determines that the pre-equivalence request has been received (step 950; Y), it activates the main control unit 6 and determines that the pre-equivalence request has not been received. If so (step 950;
N), the state is continued until the reception of the pre-equivalence request is completed.

When the main control unit 6 is activated by the reception control unit 59, the main control unit 6 causes the transmission control unit 71 of the transmission unit 7 to receive the reception station 2.
To the pre-equivalent transmission data (step 960).

Then, the data selector 71
The status, the node address, and the FCS are formed in this order, and are sequentially output to the Manchester encoding circuit 74 (step 970).

Here, the start flag area 91 which constitutes the transmission data before pre-equivalence contains the same flags as the transmission data, the pre-equivalence request, etc. which have been issued previously, and bit 0, bit 0, The information 1 and 2 contains information "(0,0,0)" indicating that the data is transmission data. In the node address area 93, the source of the pre-equivalent transmission data, that is, the node address of the local station 1 and the destination node address of the pre-equivalent transmission data are stored. The transmission data area 94 contains the original data to be transmitted, the FCS area 95 contains the CRC cyclic code generated by the FCS generation circuit, and the end flag area 96 contains the previously transmitted transmission data. Contains the same flags as the pre-equivalence request.

The Manchester encoding circuit 74 converts the start flag, the status having the pre-equivalent direction, the node address, the FCS and the end flag, which are sequentially formed, into a Manchester code and outputs it to the pre-equivalent circuit 75 (step 980).

The pre-equivalent circuit 75 reads the pre-equivalent direction latched in the register (not shown) based on the instruction of the transmission control unit 71, and widens the width of the read pulse waveform in the pre-equivalent direction by one system clock. That is, transmission data having a changed duty ratio is formed and transmitted to the receiving station 2 (step 990).

In the communication system of the first embodiment, the duty ratio of the transmission data is measured, and as a result, when the duty ratio is out of the predetermined range, the pre-equivalence request is output to the transmitting station 1, Since the transmitting station 1 receiving the request transmits the pre-equivalent transmission data to the receiving station 2 based on the pre-equivalence request, the receiving station 2 can flexibly reproduce accurate transmission data. .

Therefore, in the receiving station, the error rate of the transmission data due to the FCS check inspection and the like is reduced, so that the retransmission request of the transmission data is reduced and the transmission efficiency can be improved.

<Second Embodiment> The communication system of the second embodiment is substantially the same as the receiving unit 5, the main control unit 6 and the transmitting unit 7 provided in the transmitting station 1 and the receiving station 2 of the first embodiment. Although having the same configuration, when acting as the receiving station 2, a pre-equivalence request having different pre-equivalent magnitudes can be transmitted to the transmitting station 1 according to the distortion amount of the pulse waveform of the transmission data. Is configured. Therefore, the pre-equivalence request has a bit configuration that allows the status area 92 to indicate a pre-equivalence level indicating a plurality of pre-equivalence levels.

For example, referring to FIG. 10, the status area 92 has a size of 1 byte.
It has the following information:

Information indicating the type of the transmission frame is stored in bits 0, 1 and 2, and the contents thereof are the same as those in the first embodiment (see FIG. 4 if necessary).

Information indicating the amount of data that can be handled is stored in bit3, and the content is also the same as in the first embodiment (see FIG. 4 if necessary).

Bit 4 has information indicating the pre-equivalent direction. When it is "0", it indicates the pre-equivalence in the H level direction, and when it is "1", it indicates the pre-equivalent direction. Shows equivalence.

Information indicating the pre-equivalence level is stored in bits 5, 6 and 7. In the case of "(0,0,0)", the pre-equivalence level is set to 0, which means that the transmission data does not need to be pre-equivalent. In the case of (0,0,1), Pre-equivalent level 1 to
This means that the pulse width of the level to be in the pre-equivalent direction shown above should be widened by one system clock. In the case of (0, 1, 0) ”, the pre-equivalent level 2 In the case of (0,1,1) ", the pre-equivalent level 3 is set, and it is shown that it is widened by 3 system clocks. , 0) ”, the pre-equivalent level is set to 4 and it is indicated that it should be widened by 4 system clocks.

For example, assuming that the pre-equivalent direction is the H level direction and the transmitting station 1 receives the pre-equivalent request having the pre-equivalent level of 3, the transmission data having the duty ratio of 50% is transmitted before the pre-equivalence. As shown in FIG. 11, the transmitting station 1, which has been doing so, advances the rising edge of the H-level pulse by 3 system clocks and makes the falling edge the same as before so that the pulse width becomes 3 system clocks. Send the transmission data that has been widened.

In the second embodiment, the pre-equalization request having different pre-equivalent magnitudes can be transmitted to the transmitting station 1 according to the distortion amount of the pulse waveform of the transmission data. It is possible to obtain accurate transmission data more quickly than in the embodiment. Therefore, the transmission efficiency is also superior to that of the first embodiment.

<Third Embodiment> The communication system of the third embodiment copes with noise and temporary distortion of the transmitted wave, and therefore, when the transmitting station 1 receives a pre-equivalence request from the receiving station 2 a predetermined number of times. This is the only communication system that outputs pre-equivalent transmission data for the first time.

As shown in FIG. 12, the communication system of this embodiment has substantially the same configuration as the transmitting station 1 of the first or second embodiment, except that the receiving section 5 is different.
When the pre-equivalence requests are continuously received, the T counter 61 that counts the pre-equivalence requests and when the pre-equivalence requests are repeated a predetermined number of times, the main control unit 6 is activated via the reception control unit 59. When it is detected that the count value counted by the T counter 61 and the reference value stored in the start reference register 62 are compared with each other, and the count value is the same as the reference value. In addition, it has a comparator 63 that outputs an instruction to activate the main control unit 6 to the reception control unit 59 and clears the T counter 61 to zero.

In the third embodiment, as described above, the first
Alternatively, since the T counter 61, the activation reference register 62, and the comparator 63, which are not provided in the second embodiment, are provided, the waveform of the transmission data is distorted for a short time due to the temporary generation of noise, and at the same time the noise disappears. When the waveform of the transmission data becomes normal, the transmission efficiency is rather improved if the pre-equivalence request is not output every time the waveform is distorted.

That is, when the waveform is temporarily distorted, the pre-equivalence request corresponding thereto is issued. Even if the pre-equivalent transmission data is output based on the request, if the noise disappears immediately, The pre-equivalence request for returning is inevitably output, and the transmission efficiency is inevitably deteriorated.

<Fourth Embodiment> A communication system according to a fourth embodiment is a communication system which has a relationship between a master station and a slave station and controls connection of communication lines by a polling selecting method. When the station turns on the power and requests transmission to the slave station, that is, polls, the slave station polls the master station due to noise between the master station and the slave station, for example, reflection of a polling signal, as shown in FIG. Is a communication system in which the master station automatically sends pre-equivalent polling to the slave station when the master station cannot recognize the transmission and does not transmit the transmission response, that is, selecting.

In the communication system of this embodiment, the master station has the same configuration as that of the transmitting station 1 of the first or second embodiment, so description of the configuration will be omitted.

Next, the operation of this embodiment will be described with reference to the flow chart shown in FIG.

The master station, when the power is turned on, transmits a poll without pre-equivalence processing to the slave station (step 110),
At the same time, the reception monitoring timer is up (step 1
20) After that, it is judged whether or not selecting from the slave station which transmitted the polling for the polling is within a predetermined time (step 130).

When there is selecting from the slave station within a predetermined time (step 130; Y), the master station performs normal processing, that is, the line between the master station and slave station is connected, and normal transmission processing is performed. (Step 150), the process is terminated, and when there is no selecting within a predetermined time (step 130; N), it is determined that the slave station cannot recognize polling due to line noise, The polling in which the pre-equivalent processing for the predetermined pre-equivalent level is performed in the H level direction is transmitted to this slave station (step 140), and at the same time, the reception monitoring timer is timed up (step 160).

The master station again determines whether or not the selection for polling from the slave station which has transmitted the polling is within a predetermined time (step 170).

When there is selection from the slave station within the predetermined time (step 170; Y), the master station performs normal processing (step 180) and terminates the processing, while selecting within the predetermined time. If there is no ringing (step 170; N), it is determined whether the number of times of polling is within a predetermined number of times (step 190).

When the master station judges that the number of times of polling is less than the predetermined number of times (step 190; Y),
While returning the processing to step 140 and performing the same processing, when it is determined that the number of times is equal to or more than the predetermined number (step 19
0; N), it is determined that the pre-equivalent direction is opposite, and the polling command, which has been pre-equivalent for the predetermined pre-equivalent level in the L level direction, is transmitted again to this slave station (step 200), At the same time, the reception monitoring timer is incremented (step 210).

The master station again determines whether or not the selection for polling from the slave station which has transmitted the polling is within a predetermined time (step 220).

When there is selection from the slave station within a predetermined time (step 220; Y), the master station carries out normal processing (step 230) and ends the processing.
When there is no selecting within the predetermined time (step 220; N), it is determined whether the number of times of polling is within the predetermined number of times (step 240).

When the master station judges that the number of times of polling is less than the predetermined number of times (step 240; Y),
While returning the process to step 200 and performing the same process, when it is determined that the number of times is equal to or greater than the predetermined number (step 25
0; N), abnormal processing, that is, the communication system administrator recognizes an abnormal state of powering down the slave station, failure of the master station or slave station device, disconnection of the line and occurrence of extremely large noise, and terminates the processing. (Step 240).

In the communication system of the fourth embodiment, when the master station turns on the power and polls the slave stations, the master station automatically sends the polling with the transmission waveform shaped to the slave stations. Therefore, it is possible to determine whether the line disconnection at the time of turning on the power supply is noisy due to noise, or the line itself is disconnected due to a failure of the device itself, and post-processing becomes easy.

[0107]

As described above, according to the present invention, the receiving station measures the distortion amount of the transmission frame waveform received from the transmitting station and, if necessary, changes the duty ratio of the transmitting frame. Send an equivalence request to the transmitting station. Then, since the transmitting station transmits the transmission data whose duty ratio has been changed in advance to the receiving station based on the pre-equivalence request from the receiving station, the receiving station can reduce the influence of the waveform generated during the transmission, and the accurate The transmitted data can be reproduced.

Therefore, the receiving station does not judge that the transmission data has an error by the FCS check inspection or the like, and the transmission efficiency can be improved.

In particular, the receiving station transmits a pre-equivalence request in which the duty ratio of the transmission data is changed in accordance with the amount of distortion of the pulse waveform of the transmission data to the transmitting station. You can get the data.

Further, since the transmitting station transmits the pre-equivalent transmission frame only when the pre-equivalence request is received from the receiving station a predetermined number of times, the transmission data is transmitted only for a short time due to the temporary noise. If the waveform is distorted and there is no noise and the transmitted data waveform is normal,
Since the pre-equivalence request is not output each time, the transmission efficiency can be improved.

Further, according to the present invention, in the communication system of the polling selecting system, the master station automatically transmits the pre-equivalent polling to the slave station.
It becomes easy to judge whether the line is defective due to noise on the line or the line is defective due to the failure of the device itself, and the post-processing becomes easy.

[Brief description of drawings]

FIG. 1 is an explanatory diagram illustrating an outline of a communication system according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram illustrating Manchester codes.

FIG. 3 is an explanatory diagram showing an example of a waveform when a transmission frame waveform is converted into Manchester code.

FIG. 4 is an explanatory diagram illustrating a transmission frame used in the communication system according to the first embodiment.

FIG. 5 is a block diagram showing a configuration of a station used in the communication system according to the first embodiment.

FIG. 6 is an explanatory diagram illustrating a method of measuring a pulse level width.

FIG. 7 is an explanatory diagram illustrating a protocol of the communication system according to the first embodiment.

FIG. 8 is a flowchart illustrating a processing operation of the communication system according to the first embodiment.

FIG. 9 is a flowchart illustrating a processing operation of the communication system according to the first embodiment.

FIG. 10 is an explanatory diagram illustrating a transmission frame used in the communication system according to the second embodiment.

FIG. 11 is a diagram showing transmission data subjected to pre-equalization processing in response to a pre-equalization request.

FIG. 12 is a block diagram showing a configuration of a station used in the communication system according to the third embodiment.

FIG. 13 is an explanatory diagram illustrating a communication state when a line is defective in the fourth embodiment.

FIG. 14 is a flowchart showing a processing operation of the communication system according to the fourth embodiment.

FIG. 15 is an explanatory diagram explaining the reason why the waveform of a transmission frame is distorted.

[Explanation of symbols]

1 transmitting station 2 receiving station 3 cable 5 receiving section 51 digital filter 52 flag / status detecting circuit 53 H counter 54 L counter 55 comparator 56 synchronizing circuit 57 receiving buffer 58 FCS check circuit 59 receiving control section 61 T counter 62 starting reference register 63 Comparator 6 Main control unit 7 Transmission unit 71 Transmission control unit 72 Data selector 73 FCS generation circuit 74 Manchester coding circuit 75 Pre-equivalent circuit 90 Transmission frame (transmission data, pre-equivalence request, transmission request, transmission response, resend request) 91 Start Flag area 92 Status area 93 Node address area 94 Transmission data area 95 FCS area 96 End flag area

Claims (14)

[Claims] 1. A communication system in which a transmission station pre-equivalents a transmission waveform of a transmission frame and transmits the transmission waveform of a transmission frame to a reception station in consideration of a transmission waveform distortion when transmitting a wired line, wherein the transmission station is the transmission station. The receiving station is provided with a changing unit for changing the duty ratio of the frame, and the receiving station measures the waveform distortion amount of the transmission frame received from the transmitting station and the transmission frame waveform measured by the measuring unit. Judgment means for judging whether or not the distortion amount is within a predetermined range, and a judgment means for changing the duty ratio of the transmission frame only when the distortion amount of the transmission frame waveform is not within the predetermined range by this judgment means. A pre-equivalence requesting means for transmitting an equivalence request to the transmitting station, and a communication system. 2. The communication system according to claim 1, wherein the transmission frame is a Manchester code. 3. The transmitting station transmits a transmission frame with Manchester code and a duty ratio of 50% to the receiving station until receiving a pre-equivalence request from the receiving station. Item 1. The communication system according to Item 1. 4. The communication system according to claim 1, wherein the pre-equivalence request has information indicating a pre-equivalent direction and information indicating a pre-equivalent amount for the pre-equivalent direction. 5. The information indicating the pre-equivalent direction is information indicating that the width of either the H-level waveform or the L-level waveform is widened, and the information indicating the pre-equivalent amount. The communication system according to claim 4, wherein is a quantity that widens the width of the waveform. 6. The communication system according to claim 5, wherein the pre-equivalent amount is in units of system clock frequencies. 7. The communication system according to claim 1, wherein the transmitting station and the receiving station have the same system clock frequency. 8. The communication system according to claim 1, wherein said measuring means measures waveform distortion with a transmission waveform indicated by status information of said transmission frame. 9. The measuring means converts the H level pulse width and the L level pulse width in a predetermined pulse cycle in the transmission frame by the number of outputs of the system clock, and the converted H level pulse is obtained. The difference between the number of system clock outputs and the number of L level pulse system clock outputs,
The communication system according to claim 1, wherein the amount of distortion of the transmission frame waveform is measured. 10. The communication system according to claim 9, wherein the predetermined pulse cycle is a pulse cycle indicated by status information of the transmission frame. 11. The pre-equalization requesting means transmits a pre-equalization request to the transmitting station, the pre-equalization request having different changes in the duty ratio of the transmission frame according to the distortion amount of the pulse waveform of the transmission data. The communication system according to claim 1, characterized in that 12. The transmission station transmits a pre-equivalent transmission frame to the receiving station only when a pre-equivalence request is received from the receiving station a predetermined number of times.
A communication system as described. 13. A communication system having a relationship between a master station and a slave station and using a polling selecting method, wherein the master station automatically transmits pre-equivalent polling to the slave station. Communication system. 14. The communication system according to claim 13, wherein the polling subjected to the pre-equalization process is transmitted by the master station when the power is turned on.