JPH09247198A - Star type data transmitter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To utilize the carrier sense multiple access with collision detection(CSMA/CD) system in compliance with the standards while ensuring real time performance by sending a dummy frame to each station and selectively sending the dummy frame so as to disable transmission by a station equipment. SOLUTION: A dummy frame is generated from a dummy generating section 13 and given to a hub basic function section 11 through a dummy frame input signal 25 and sent to each station equipment via a transmission data line 21. The dummy frame input signal 25 received by the hub basic function section 11 is sent to all station equipments 51-54. Then transmission inhibit sections 17, 19 controls a specific one station equipment to inhibit transmission based on a dummy frame control signal 23 received from a dummy transmission control section 12. The station equipment not receiving the dummy frame input signal 25 to attain data transmission because it has a token. The station equipment having a token sends a transmission frame to the hub device 10 through transceivers 26, 27.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a star-type data transmission device in which a plurality of station devices are connected in a star shape around a hub device via a transmission line to mutually transmit data.

[0002]

2. Description of the Related Art IEEE 80, which is the mainstream of the current LAN
2.3 method (Insertnet) is CSMA / CD (C
aria Sensa Multi Acces / Co
Media access control, which is an abbreviation for "Listen Detect" (XEROX Ethernet). In the CSMA / CD, each station device monitors the signal on the common transmission path and transmits it if there is a free space for a certain period of time, and if there is no free space, delays the transmission until it becomes available. Also, during transmission, it is monitored whether there is a collision with another station, and if a collision occurs, the transmission is interrupted and the transmission is performed again with a delay of a predetermined time. Due to such CSMA / CD operation, when the usage rate of the transmission path becomes high, collisions frequently occur, or there are cases where transmission cannot be performed forever. Therefore, it is not suitable for applications requiring real-time performance.

In order to realize the real-time property that information can be exchanged reliably within a fixed time, IEEE802.4
A method of adopting a token-passing type media access control unit represented by the standard, and Japanese Patent Publication No. 4-39819.
And a function for transmitting to an IEEE802.3 system station device in which a transmission delay is not compensated without causing a collision, and an HDLC (High)
Level Data Link Control)
A system in which a media access function is added to a device having no media access control function such as a system has been used so far.

[0004]

However, the above-mentioned conventional token passing system is not widely used and the equipment is expensive. In addition, there are few types of equipment prepared, and new development is necessary as necessary. Furthermore, the method of adding functions to the station device of IEEE802.3 is not a standard, so that various station devices need to be independently developed, resulting in high cost.

Therefore, the present invention provides a star-type data transmission device which can be used as it is by a standard-compliant CSMA / CD system station device while ensuring real-time performance by a method of adding a function to IEEE802.3. To aim.

[0006]

In order to achieve the above object, the invention according to claim 1 provides a transmission line of a hub device,
In a star type data transmission device in which a plurality of station devices having a CSMA / CD system media access control are connected in a star shape, a configuration in which a dummy frame containing no data information can be transmitted from the hub device to each station device The star-type data transmission device is characterized in that means for disabling transmission of the station device by selectively transmitting the dummy frame to each of the station devices is added.

In order to achieve the above-mentioned object, the invention according to claim 2 is a star type in which a plurality of station devices having a CSMA / CD system media access control are connected in a star shape to a transmission path of a hub device. In the data transmission device, a dummy frame containing no data information can be transmitted from the hub device to all station devices other than a specific one station device of the station devices, and transmission can be performed only to the specific one station device. The star-type data transmission device is characterized in that, when the specific one-station device starts transmission of a transmission frame, transmission of the dummy frame is stopped, and means for relay-transmitting the transmission frame to all-station devices is added. Is.

According to the invention corresponding to claim 1 or claim 2, pseudo token passing can be realized without changing the media access method of the IEEE802.3 standard. In the IEEE802.3 standard media access system, that is, the CSMA / CD system, the station device cannot always transmit within a certain time. On the other hand, the token passing system enables real-time transmission because the transmission right is always sent within a fixed time. Therefore, the transmission device is effective for a device requiring real-time property such as a control LAN.

In order to achieve the above-mentioned object, the invention according to claim 3 is a star type in which a plurality of station devices having media access control of CSMA / CD system are connected in a star shape to a transmission line of a hub device. In the data transmission device, when transmission of a specific station device by the transmission right control function is completed, the transmission right is transferred to the station device by transmitting a dummy frame from the hub device excluding another one station device, and this operation is performed. It is a star type data transmission device characterized in that means for circulating the transmission right to each station device is added by repeating in a predetermined order.

According to the invention corresponding to claim 3, the transmission order of the station device is set in advance, and when the transmission is started, the transmission right is given to the station device having the first transmission order. The transmission right is circulated in a preset order, the transmission right is returned to the first station device when the transmission of the last station device is completed, and the transmission right is repeated in the same order. By transmitting the method shown here as an example in an arbitrary order, the transmission right can be circulated in a preset order.

In order to achieve the above object, the invention according to claim 4 is characterized in that an interval between the dummy frame and the transmission frame or between the dummy frame and the dummy frame is set to an interframe interval of a CSMA / CD system. 3. The star-type data transmission device according to claim 2, wherein by making the size smaller, a frame collision caused by simultaneous transmission from the plurality of station devices and a dead time associated therewith are avoided.

According to the invention corresponding to claim 4, the interframe interval provided between the dummy frame and the transmission frame or between the dummy frame and the dummy frame is CSMA.
In order to prevent the frame collision seen in the / CD method, the intervals between the frames are set to be equal to or more than the interframe interval. As a result, frame collision can be avoided and the transmission efficiency can be improved.

In order to achieve the above object, the invention according to claim 5 provides the transmission right to a certain station device a plurality of times per revolution, and to another station device once per a plurality of revolutions. The star type data transmission apparatus according to claim 3, wherein the station data is given to the station apparatus in an arbitrary order so that each station can be given a transmission priority.

According to the invention corresponding to claim 5, a plurality of transmission rights are given in one round to increase the priority of a specific station device, and transmission rights are given in an arbitrary order to lower the priority. As a result, it is possible to give priority to transmission for each station device.

In order to achieve the above object, the invention according to claim 6 monitors the transmission time transmitted by the station device at one time, and a difference between a transmission start time of the last time and the transmission start time of this time and a target. 4. The maximum circulation time is controlled by calculating the transmission permission time from the circulation time and transferring the transmission right to the next station device at the end of the frame that has exceeded the transmission permission time. Is a star type data transmission device.

According to the invention corresponding to claim 6, by controlling the transmission permission time per station by the circulation timer,
The maximum lap time can be made almost constant. In order to achieve the above object, the invention according to claim 7 is such that, in the hub device, the number of frames transmitted by the station device at one time is monitored, and when the predetermined number of frames is completed, the next station is transmitted. 4. The star type data transmission device according to claim 3, wherein the maximum circulation time is controlled by transferring the transmission right to the device.

According to the invention corresponding to claim 7, the maximum round-trip time can be made substantially constant by monitoring the number of frames transmitted at one time by the station device. In order to achieve the above-mentioned object, the invention according to claim 8 is to monitor a transmission time period in which the station device transmits at one time, and when the transmission end time of a frame which has reached a predetermined time or more 4. The star-type data transmission device according to claim 3, wherein the maximum circulation time is controlled by transferring the transmission right to.

According to the invention corresponding to claim 8, the maximum circulation time can be made substantially constant by monitoring the transmission time that the station device transmits at one time. In order to achieve the above object, the invention according to claim 9 starts the orbit in synchronism with a reference clock given from the inside or the outside of the hub device, and outputs a dummy frame when one orbit ends and then outputs the dummy frame. 4. The star-type data transmission device according to claim 3, wherein the circulation is stopped until the reference clock of 2. comes.

According to the invention corresponding to claim 9, by synchronizing the transmission circulation operation with an external reference clock, the circulation can be started and stopped in synchronization with the application software using this transmission device. it can.

In order to achieve the above-mentioned object, the invention according to claim 10 performs transmission control operation in the hub device even if the transmission right is not given, or after receiving the transmission right. 4. The star type data transmission device according to claim 3, wherein the station device that never stops transmitting is logically or physically separated from the hub device. According to the invention corresponding to claim 10,
The abnormal port can be logically or physically disconnected from the hub device.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a star type data transmission device according to the present invention will be described below with reference to FIGS. 1 to 5. FIG. 1 is a basic system configuration diagram of the present invention.

The basic system of the present invention is the hub device 1.
0 and the station devices 51, 52, 53, 54, and the cables 31, 3 connecting the hub device 10 and the station devices 51, 52, 53, 54.
It is composed of 2, 33, and 34.

The hub device 10 includes a station device having a CSMA / CD system media access control, a cable 31,
It is connected in a star shape via 32, 33 and 34. The cables 31 to 34 use twisted pairs or optical cables.

FIG. 2 is a diagram for explaining the configuration of the hub device 10. The hub basic function unit 11 relays or retransmits a received frame, and the dummy frame control for controlling the transmission of the dummy frame. A dummy transmission control unit 12 that outputs a signal 23, a dummy generation unit 13 that generates a dummy frame input signal 25 and supplies it to the hub basic function unit 11, a transmission time per transmission of the station device and an abnormal state monitoring, disconnection instruction, A transmission monitoring unit 14 that controls the hub basic function unit 11 such as the circulation of the transmission right and the priority of the station device, a circulation timer unit 15 that measures the circulation time, an external reference clock unit 16 that gives a reference clock, and a specific station device. Transmission prohibition units 17 and 19 and reception detection units 18 and 20, which prohibit transmission of dummy frames, for example, station devices 51 and 54, and cables 31 and 34, respectively. Transceiver unit 26, 27,
A transmission data line 2 that connects between the hub basic function unit 11, the transmission prohibition units 17 and 19, and the reception prohibition units 18 and 20, respectively.
1 and the reception data line 22.

The hub basic function unit 11 is IEEE802.3.
A compliant CSMA / CD hub controller is used. In order to give the CSMA / CD system hub controller real-time performance, a dummy frame is used to give a transmission right to only one specific station.
The dummy frame is generated by the dummy generation unit 13, is input to the hub basic function unit 11 through the dummy frame input signal 25, and is transmitted to each station device via the transmission data line 21.

However, the dummy frame input signal 25 input to the hub basic function unit 11 is transmitted to all the station devices 51-5.
4 is transmitted, the transmission prohibition units 17 and 19
A dummy frame control signal 23 output from the dummy transmission control unit 12 controls not to transmit only a specific one-station device. Since the station device that does not receive the dummy frame input signal 25 has the transmission right, data can be transmitted.

The station device having the transmission right is the transceiver unit 2
The transmission frame is transmitted to the hub device 10 via 6 and 27. This transmission frame is input to the hub basic function unit 11 via the reception data line 22, and in response to this, the hub basic function unit 11 outputs the transmission frame to all station devices except the station device that transmitted the transmission frame. At this time, if the dummy frame is not stopped, the transmission frame cannot be output.

Therefore, the station device (51
To any of 54 to 54), the transmission detection section 18 and 20 detect the transmission frame to stop the dummy frame and notify the transmission monitoring section 14 through the reception detection signal 24. Upon receiving the detection of the transmission frame, the transmission monitoring unit 14 instructs the dummy transmission control unit 12 to end the dummy frame and stop the dummy frame transmission. The transmission frame sent to the hub basic function unit 11 via the reception data line 22 by the cancellation of the dummy frame is the transmission data line 21.
Through, to all station devices that do not have the transmission right.

The transmission permission period of the station device having the transmission right depends on the time permitted from the circulation time by the circulation timer unit 15, the transmission time permitted by the transmission monitoring unit 14 per transmission right, and the maximum number of frames. Given.

FIG. 3 is an example of a transmission frame used in the embodiment of the present invention. In FIG. 3, four A, B, C, and D station devices 51 to 54 are connected to the hub device 10, and each station device 5
This is a state of a transmission frame when 1 to 54 is permitted to transmit one transmission frame with one transmission right.
The transmission right circulates in order from the station A device to the station B device, the station C device, and the station D device, and no priority is set.
Also, the shaded frames in the figure are dummy frames, the white frames are transmission frames, and ti is the interframe interval.

Time elapses from left to right in the figure. First, the transmission right is given to the station A device, and after an interframe interval is opened, a dummy frame is transmitted from the dummy generation unit 13. At this time, the dummy frame is received by all the stations except the station A device. While the station A device does not transmit the transmission frame, continues transmitting dummy frames,
After a certain period of time, transmission of the dummy frame ends, and the transmission right is transferred to the next station device.

Next, a dummy frame is transmitted after the interframe interval is opened, but the interframe interval should not be longer than the interframe interval of the CSMA / CD system. When the transmission right is transferred to the B station apparatus, the B station apparatus has the transmission data, and therefore the transmission frame is transmitted after the inter-frame interval of the CSMA / CD system is exceeded.
Send to 0. When the hub device 10 detects the transmission frame from the B station device, it immediately stops the dummy frame transmission and transmits the transmission frame to a device other than the station device having the transmission right. After the transmission of the B station device is completed, the transmission right is transferred to the C station, the inter frame interval is opened, and the dummy frame is transmitted. The same operation is performed by the C station device and the D station device, and after the transmission right of the D station device is completed, the transmission right is transferred to the A station device. In this way, the transmission right circulates.

FIG. 4 shows the data layer / permission time per transmission right. In this figure, a condition for permitting the transmission of a plurality of frames per one transmission right is added to the example of the transmission frame of FIG.

Here, the case where the transmission of the station D is completed and the transmission right is transferred to the station A is shown. Explaining the limitation by the maximum number of transmission frames in this example, when the maximum number of frames is set to 3, the transmission monitoring unit 14 counts the number of transmission transmission frames of the A station from the time when the transmission right is transferred to the A station, Upon the end of the third transmission frame, the transmission right of station A is terminated.

Similarly, the transmission right permission time is limited by the limit value by turning on the timer in the transmission monitoring unit 14 at the stage when the transmission monitoring unit 14 transfers the transmission right to the station A device and measures the transmission time. The transmission right is terminated when the limit value determined in advance is exceeded, but if the transmission frame is being transmitted at the limit value stage, the transmission right is terminated with the end of the transmission. In this way, each station device controls the transmission time individually by the limitation by the maximum number of transmission frames and the control by the limit value of the transmission permission time, and keeps the maximum circulation time constant.

In the transmission time control method, each control is performed independently, and if any one of the conditions is met,
Perform individual control. In addition, there is no priority when controlling.

FIG. 5 shows the transmission timing by the external reference clock unit 16. Upon receiving the reference clock from the external reference clock unit 16, the transmission monitoring unit 14 hands over the transmission right to the station device in an arbitrarily determined order. In the case of the figure, the transmission is first started from the station A device, and when the transmission time of the station A device is completed, the transmission right is handed over to the station B device.
This operation is continued up to the D station device, but when the transmission of the D station device is completed, that is, when the transmission for one round is completed earlier than the external reference clock, the transmission is stopped. Then, when the next reference clock is generated, the transmission of the station apparatus at that time is ended, the transmission of the round is ended, and the next round is started. With this method, the maximum lap time can be kept almost constant.

According to the embodiment described above, the IEEE
Pseudo token passing can be realized without changing the media access method of the 802.3 standard. IEEE802.3 standard media access method,
That is, in the CSMA / CD system, the station device cannot always transmit within a fixed time. On the other hand, the token passing system enables real-time transmission because the transmission right is always sent within a fixed time. Therefore, the transmission device is effective for a device requiring real-time property such as a control LAN.

The present invention is not limited to the above-described embodiments, but can be modified and implemented as follows. (1) In the above-described embodiment, it is assumed that the transmission right always goes to each station device in one round, but the transmission right may be given multiple times in one round, or once in several rounds. Then, a priority can be set for a specific station device. Specifically, the transmission unit monitoring unit 14 in FIG. 2 is given a transmission right to a specific station device a plurality of times per revolution, or is given to another station device once per a plurality of revolutions. It is possible to give priority to transmission to each station apparatus by giving it to the station apparatus. In this case, in order to increase the priority of the specific station device, a plurality of transmission rights may be given in one round, and in order to decrease the priority of the specific station device, the transmission rights may be given in any order. The priority setting must be set before the hub device 10 starts transmission.

(2) By controlling the transmission permission time per one station device by the circulation timer unit 15, the maximum circulation time can be made almost constant. Specifically, the transmission time that the station device transmits at one time is monitored, and the transmission permission time is calculated from the difference between the time when the last transmission was started and the time when this transmission is started, and this difference and the target lap time. However, by shifting the transmission right to the next station at the end of the frame that has exceeded the transmission permission time, the maximum circulation time can be made almost constant. This is executed by controlling the transmission time by the transmission monitoring unit 14 in FIG.

(3) The maximum round-trip time can be made almost constant by monitoring the number of frames transmitted by the station device at one time. Specifically, the number of frames may be monitored, and the transmission right may be transferred to the next station device when the number of frames exceeds a certain level.

(4) The maximum circulation time can be made almost constant by monitoring the transmission time that the station device transmits at one time. Specifically, the transmission time transmitted by the station device at one time may be monitored, and the transmission right may be transferred to the next station device at the end time of the frame that has exceeded a certain level.

(5) In FIG. 2, the station devices 51 to 54 having an abnormality (transmitting although the transmission right is not given, or the transmission right control operation is performed after the transmission right is received) A station device that does not stop transmission) can be logically or physically separated from the hub device 10. Specifically, the transceiver units 26 and 27 and the transmission prohibition unit 1 of FIG.
A contact is put between 7 and 19 or a switch is put between the hub basic function unit 11 and the station devices 51 to 54.
Then, the transmission monitoring unit 14 monitors the abnormal state of the station device,
If an abnormality occurs, the hub basic function unit 11 is notified and the station device is logically disconnected, or the transmission monitoring unit 1 is directly connected.
4 may be configured to operate the disconnection switch to physically disconnect it, and disconnect the abnormal station device. As a result, safe data transmission can always be guaranteed. Furthermore, by configuring the detached station device to return to the connected state by the reset switch, it is possible to easily perform the restoration of the station device after repairing the faulty station device.

(6) The external reference clock section 16 of FIG.
It is not necessarily outside the hub device 10 as in the embodiment,
A reference clock provided from the inside of the hub device 10 can be similarly implemented. Specifically, it may be anything as long as it starts the circulation in synchronization with the reference clock, and when one circulation is completed, the circulation is stopped until the next reference clock arrives while outputting a dummy frame.

[0045]

According to the present invention, the following effects can be obtained. That is, the pseudo token passing can be realized without changing the media access method of the IEEE802.3 standard. In the IEEE802.3 standard media access system, that is, the CSMA / CD system, the station device cannot always transmit within a certain time. On the other hand, the token passing system enables real-time transmission because the transmission right is always sent within a fixed time.
Therefore, the transmission device is very effective for devices requiring real-time property such as a control LAN.

The hub device of the present invention is IEEE80.
All that is required is to add a real-time control media access control function to the 2.3-compliant hub controller, and the station device can use the inexpensive device that is compliant with international standards and is popular.

Further, when it is desired to set the priority to the specific station device, the priority can be easily set by giving the transmission right a plurality of times in one round. On the contrary, when it is desired to lower the priority of the station device than that of other station devices, it can be easily executed by giving the station device a transmission right once every several turns.

[Brief description of drawings]

FIG. 1 is a basic system configuration diagram of a star type data transmission device of the present invention.

FIG. 2 is a block diagram showing the configuration of the hub device of FIG.

FIG. 3 is a time chart showing an example of a transmission frame used in FIGS. 1 and 2.

FIG. 4 is a time chart showing an example of a data transmission permission time of the station device permitted per one transmission right of FIG.

5 is a time chart showing the transmission timing by the external reference clock of FIG.

[Explanation of symbols]

 10 ... Hub device, 11 ... Hub basic function unit, 12 ... Dummy transmission control unit, 13 ... Dummy generation unit, 14 ... Transmission monitoring unit, 15 ... Circulation timer unit, 16 ... External reference clock unit, 17, 19 ... Transmission prohibited Part, 18, 20 ... Reception detection part, 21 ... Transmission data line, 22 ... Reception data line, 23 ... Dummy frame input signal, 24 ... Reception detection signal, 25 ... Dummy frame input signal, 26, 27 ... Transceiver part, 31 , 32, 33, 34 ... Cables, 51, 52, 53, 54 ... Station devices.

Claims (10)

[Claims] 1. A star type data transmission apparatus in which a plurality of station apparatuses having a CSMA / CD system media access control are connected in a star shape to a transmission path of the hub apparatus, wherein the hub apparatus is connected to each station apparatus. A star-type data transmission characterized in that a dummy frame that does not include data information can be transmitted, and means for disabling transmission of the station device by selectively transmitting the dummy frame to each station device is added. apparatus. 2. A star-type data transmission device in which a plurality of station devices having media access control of CSMA / CD system are connected in a star shape to a transmission line of the hub device, wherein the hub device specifies one of the station devices. All the station devices except the one station device are transmitted a dummy frame containing no data information to enable transmission only to the specific one station device, and the specific one station device starts transmission of the transmission frame. Then, the star-type data transmission device is characterized in that the transmission of the dummy frame is stopped and a unit for relay-transmitting the transmission frame to the all-station device is added. 3. A star-type data transmission device in which a plurality of station devices having media access control of CSMA / CD system are connected in a star-like manner to a transmission path of a hub device. When the transmission is completed, a dummy frame is transmitted from the hub device except for another one station device to transfer the transmission right to that station device, and by repeating this operation in a predetermined order, the transmission right is circulated to each station device. A star-type data transmission device, characterized in that a means for causing it is added. 4. Simultaneous transmission from the plurality of station devices by setting an interval between the dummy frame and the transmission frame or between the dummy frame and the dummy frame to be smaller than an interframe interval of the CSMA / CD system. 3. The star-type data transmission device according to claim 2, wherein the frame collision caused by the above and a dead time associated therewith are avoided. 5. By giving the transmission right to a station device in any order, for example, to a certain station device a plurality of times per revolution, and to another station device once in a plurality of revolutions 4. The star-type data transmission device according to claim 3, wherein the data transmission device has a priority of transmission. 6. The transmission time transmitted by the station device at one time is monitored, the transmission permission time is calculated from the difference between the previous transmission start time and the current transmission start time, and the target circulation time, and the transmission permission time is equal to or more than the transmission permission time. 4. The star-type data transmission device according to claim 3, wherein the maximum circulation time is controlled by transferring the transmission right to the next station device at the end of the frame. 7. In the hub device, the station device is 1
By monitoring the number of frames to be transmitted each time, and when the predetermined number of frames is completed, the transmission right is transferred to the next station device,
4. The star type data transmission device according to claim 3, wherein the maximum circulation time is controlled. 8. The maximum round-trip time can be reduced by monitoring the transmission time that the station device transmits at one time and transferring the transmission right to the next station device at the end of transmission of a frame that has reached a predetermined time or more. The star type data transmission device according to claim 3, wherein the star type data transmission device is controlled. 9. A method for starting rotation in synchronism with a reference clock supplied from the inside or outside of the hub device, and stopping the rotation until the next reference clock arrives while outputting a dummy frame when one rotation is completed. The star-type data transmission device according to claim 3, characterized in that 10. The hub device, wherein the hub device is configured to perform transmission even if a transmission right is not given or to stop transmission despite performing a transmission control operation after receiving the transmission right, 4. The star type data transmission device according to claim 3, which is logically or physically separated from the device.