JP2844709B2 - Communication control device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a communication control device for transmitting and receiving data and the like via a communication circuit, and more particularly to improving the reliability of a transmission system.

<Conventional Technology> Data is exchanged between communication control devices connected via a communication circuit based on the following method.

That is, in the case of one-to-one communication such as point to point,
In response to the transmission of a command frame by the communication control device on the transmitting side (hereinafter, referred to as “transmission station”), the communication control device on the receiving side (hereinafter, referred to as “receiving station”) responds by returning a response frame. .

At this time, in order to avoid duplicate reception of the same command frame, if the transmitting station does not receive the response frame from the receiving station normally, it requests a retransmission of the response frame instead of retransmitting the command frame. A response retransmission request frame is sent out.

In a system such as a multipoint system in which three or more communication stations are connected to a communication line, a command number is added to a command frame in order to avoid duplicate reception of the same command frame.・ The frame is retransmitted.

<Problems to be solved by the invention> However, in the former method of transmitting a response retransmission request frame, due to the influence of noise or the like,
The receiving station that has received the response retransmission request frame may return a response frame corresponding to the previously received command frame according to the command frame to be responded to immediately before, so that the current command frame is There was a risk of disappearance.

Further, in the latter method in which three or more communication stations are provided and a sequence number is added to a command frame and transmitted, when transmitting and receiving a command frame, the transmitting station and the receiving station respectively communicate with each other. There is a problem that the total number of communication stations is limited because information is managed for each communication station.

An object of the present invention is to solve the problems as described above, and can avoid the duplicate reception of command frames regardless of the number of communication stations, and eliminate the loss of command frames. An object is to obtain a high communication control device.

<Means for Solving the Problems> According to the present invention, which solves the above problems, a sequence bit is added to a frame to be transmitted, and a frame to be transmitted is determined according to the sequence bits in the received frame. The specific configuration is as follows.

That is, a command frame is transmitted to a partner station connected by a communication line, and the command station is transmitted from the partner station.
A transmission function for transmitting a response retransmission request frame when a response frame corresponding to the frame cannot be received, and transmitting a command frame identical to the command frame when receiving a command retransmission request frame from the partner station. And receiving the command frame,
When the command frame is normally received, the response frame is returned, and when the response retransmission request is received, the communication control device having a reception function of transmitting the response frame. A sequence bit to be inverted every time transmission is added to the command frame, and the same sequence bit as the sequence bit added to the command frame transmitted immediately before when transmitting the response retransmission request frame is added to this command bit. A sequence bit generation adding means for adding to the response retransmission request frame is provided in the transmission function, the sequence bit added to the received command frame is stored, and internally when the response retransmission request frame is received. Remembered sequence
A communication control apparatus characterized in that the reception function is provided with sequence bit storage means for comparing with the bit value and instructing transmission of a response frame when they match and instructing transmission of a command retransmission request frame when they do not match. It is.

Also, the transmission function transmits the command frame and the response retransmission request frame with the transmission source address of its own station added, and transmits the transmission source address.The reception function stores the transmission source address, and transmits the response retransmission request. When a frame is received, the sequence bits and the transmission source address in the response retransmission request frame are compared with the sequence bits and the transmission source address stored therein. May be provided, and a comparison means for instructing transmission of a command retransmission request frame when either one does not match may be provided.

<Operation> The communication control device of the present invention operates as follows.

(1) The transmission function adds a sequence bit when transmitting a command frame and a response retransmission request frame. Upon receiving the response retransmission request frame, the reception function transmits a response frame or a command retransmission request frame according to the added sequence bits and the internally stored sequence bit values.

(2) The transmission function adds a transmission source address together with a sequence bit when transmitting a command frame and a response retransmission request frame. When the response function receives the response retransmission request frame, the response function or the command retransmission request frame is determined based on the added sequence bits and transmission source address and the internally stored sequence bits and transmission source address values. Is sent.

<Embodiment> FIG. 1 is a block diagram showing a configuration of a communication control device embodying the present invention.

The communication control device 1 is connected to a communication line L, and internally includes a transmission function 2, a reception function 3, an interface function 4 with the communication line L, and other functions 5 necessary for transmission and reception.

The transmission function 2 generates a command frame and transmits the command frame together with the transmission source address. Each time a command frame is transmitted, the sequence bit sb is inverted and added to the command frame. Sequence bit management unit 22, which stores
If normal reception was not successful when receiving a response frame, a response retransmission request frame is sent out.
Also, it has a command retransmitting unit 23 for retransmitting a command frame when receiving a command reproduction request frame.

The receiving function 3 includes a frame receiving unit 31 that receives a command frame, a storage unit 32 that stores a sequence bit sb included in the command frame and a transmission source address SA,
When a command frame is normally received, a response frame is transmitted, and when a response retransmission request frame is received, a sequence bit sb added therein and a sequence bit sb internally storing a source address SA
And a response retransmission unit 33 for transmitting a response frame or a command retransmission request frame in comparison with the transmission source address SA.

FIG. 2 is an example in which the communication control devices 1 of the present invention perform one-to-one data transmission via the communication line L.

The transmission / reception operation at this time will be described with reference to the operation diagram of FIG.

In addition, the address of one communication control device 1 is set as N and the transmitting station is set, and the address of the other communication control device 1 is set as N + 1 and the receiving station is set.

In FIG. 3, in the case of (1) normal operation, (2) when a response frame is not received and recovery is made by a response retransmission request, (3) a response retransmission request is transmitted without response frame transmission due to noise and a command retransmission request is issued. The case of recovery will be described in three cases.

(1) When a command transmission request is generated in the transmitting station, the sequence bit sb is inverted (in this example, inverted from “1” to “0”), and the command frame CF1 is transmitted. The sequence bit sb “0” and the source address AS “N” are added to the command frame CF1.

This allows the receiving station to determine the sequence bit sb
“0” and the source address SA “N” are set, and the command frame CF1 is captured by the receiving station. The response frame RF1 is transmitted from the receiving station to the transmitting station, and the command transmission operation ends.

(2) When a command transmission request is generated at the transmitting station, the sequence bit sb is inverted from “0” to “1”, and the command
The frame CF2 is transmitted with the sequence bit sb "1" and the transmission source address SA "N" added. The receiving station sets the sequence bit sb “1” and the source address SA “N”, fetches this command frame CF2,
Transmits frame RF2.

Here, noise z1 is added to the response frame RF2,
If not transmitted to the transmitting station correctly, the transmitting station transmits to the receiving station a response retransmission request frame RR2 to which the same sequence bit sb "1" and the source address SA "N" as the command frame CF2 are added. .

The receiving station internally stores the sequence bit sb “1” and the source address SA “N” added to the response retransmission request frame RR2 in the sequence bit.
The sb “1” is compared with the transmission source address SA “N”, and a response frame RF2 ′ to the command frame CF2 is transmitted to the transmission station because they match. Thus, the command transmission operation ends.

(3) A command transmission request is generated at the transmitting station, the sequence bit sb is inverted from “1” to “0”, and the sequence bit sb “0” and the transmission source address SA “N” are added to the command.・ Send frame CF3 to the receiving station.

At this time, it is assumed that noise z2 is present in this command frame CF3, transmission cannot be performed normally at the receiving station, and noise z3 is received at the transmitting station.

As a result, the transmitting station could not receive the response frame corresponding to the command frame CF3, and thus added the sequence bit sb “0” and the source address SA “N” and sent the response retransmission request frame RR3 to the receiving station. Send out.

In the receiving station, the received response retransmission request frame RR
Sequence bit sb “0” in 3 and source address SA
“N” and the internally stored sequence bit sb “1”
And the source address SA “N”, and because the sequence bit sb does not match, a command retransmission frame is sent to the transmitting station.
Send CR.

This causes the transmitting station to re-enter command frame CR3
The same command frame CF3 'to the receiving station,
The receiving station sets the sequence bit sb "0" and the source address AS "N" in the command frame CF3 'internally, and fetches this command.

Then, the receiving station sends a response frame RF3 to the transmitting station.
And the command transmission operation ends.

In the above operations (1), (2) and (3),
Since transmission / reception is performed between one-to-one communication control devices (transmitting station and receiving station), the address of the transmitting station, that is, the source address SA
“N” may or may not be added.

Now, next, as shown in FIG. 4, the address "N",
The communication between three or more communication control devices, in which the "N + 1" and "N + 2" communication control devices 1 are connected to the communication line L, will be described with reference to the operation diagram of FIG.

This figure shows that the addresses “N” and “N + 2” as transmitting stations,
Communication between three stations with address "N + 1" as a receiving station,
(1) is a communication between the transmitting station “N” and the receiving station “N + 1”,
(2) is communication between the transmitting station “N + 2” and the receiving station “N + 1”.

(1) A command transmission request is generated from the transmission station "N", and the inverted sequence bit sb "0" and the transmission source address SA
“N” is added to the command frame CF1 and transmitted to the receiving station.

The receiving station “N + 1” stores the sequence bit sb “0” and the transmission source address SA “N” internally, fetches this command, transmits the response frame RF1 to the transmitting station, and successfully executes the command transmission operation. finish.

(2) Next, it is assumed that a command transmission request has occurred at the transmitting station “N + 2”.

The transmitting station “N + 2” has the inverted sequence bit sb
Command frame with “0” and source address SA “N + 2”
Add to CF2 and transmit to receiving station "N + 1".

At this time, the receiving station “N + 1” cannot normally receive this command frame CF2 due to the noise z1, and the transmitting station “N + 1”
The noise z2 is also given to “+2”.

After transmitting the command frame CF2, the transmitting station “N + 2” does not return a corresponding response frame, so the sequence bit sb “0” similar to the command frame CF2 is transmitted.
Then, a response retransmission request RR2 is transmitted to the receiving station "N + 1" with the transmission source address SA "N + 2" added.

The receiving station “N + 1” transmits the sequence bit sb “0” in the response retransmission request RR2 and the source address SA “N +
2 "is compared with the internally stored sequence bit sb" 0 "and the source address SA" N ".

As a result of the comparison, the value of the sequence bit sb matches “0”, but the value of the source address SA differs between “N” and “N + 2” and does not match, so that the transmitting station (“N + 2”) On the other hand, it sends out a command retransmission request frame CR.

The transmitting station "N + 2" which has received the command reproduction request frame CR transmits the same command frame CF2 'as the previously transmitted command frame CF2 to the receiving station "N + 1".

As a result, the receiving station “N + 1” has the sequence bit sb
This command is fetched by setting “0” and the source address SA “N + 2”, a response frame RF2 is transmitted to the transmitting station “N + 2”, and the command transmission operation is completed.

In this way, even if the number of communication stations is three or more, transmission / reception operations can be performed smoothly without loss of command frames and duplicate reception.

<Effects of the Invention> As described above, according to the communication control device of the present invention, even in a one-to-one communication operation or a communication operation of three or more stations,
Duplicate reception of the same frame, loss of a command frame, and the like can be eliminated, and a more reliable communication control device can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a communication control device embodying the present invention, FIG. 2 is a diagram showing a one-to-one connection of the device of the present invention, and FIG. 3 is a transmission / reception operation of a one-to-one communication control device. FIG. 4 is a diagram showing the connection of three units of the device of the present invention;
FIG. 5 is a diagram showing an example of the transmission / reception operation in the connection shown in FIG. DESCRIPTION OF SYMBOLS 1 ... Communication control apparatus, 2 ... Transmission function, 21 ... Frame transmission part, 22 ... Sequence bit management part, 23 ... Command retransmission part, 3 ... Reception function, 31 ... Frame reception part, 32 ..... storage unit, 33 ..... response resending unit, 4 ... interface function, 5 ... other functions, L ..... communication line.

Claims (2)

(57) [Claims] A command frame is transmitted to a partner station connected by a communication line, and when a response frame corresponding to the command frame cannot be received from the partner station, a response retransmission request frame is transmitted. ,
When a command retransmission request frame is received from the partner station, a transmission function of transmitting the same command frame as the command frame, and when the command frame is received, and when the command frame is normally received, the A communication control device having a function of transmitting a response frame and receiving the response retransmission request, and having the function of transmitting the response frame. A sequence bit generation addition for adding to the frame a sequence bit identical to the sequence bit added to the command frame transmitted immediately before transmission of the response retransmission request frame to the response retransmission request frame Means to the transmission function And storing the sequence bits added to the received command frame and comparing it with the internally stored sequence bit value when the response retransmission request frame is received. A communication control device, wherein a sequence bit storage means for instructing frame transmission and instructing transmission of a command retransmission request frame when they do not match is provided in the reception function. 2. The transmission function transmits the command frame and the response retransmission request frame with a transmission source address of the own station added thereto, and stores the transmission source address in the reception function. When the response retransmission request frame is received, the sequence bits and the transmission source address in the response retransmission request frame are compared with the internally stored sequence bits and the transmission source address. The communication control device according to claim 1, further comprising comparison means for instructing frame transmission and instructing transmission of a command retransmission request frame when either of them does not match.