JPS62221236A - Data transmission equipment - Google Patents

Abstract

PURPOSE:To maintain system function by inhibiting repeat normally in one of plural node stations connected into a loop by a pair of clockwise and counterclockwise transmission lines but starting repeat there if abnormality occurs. CONSTITUTION:Plural nodes 101-10n are connected into a loop by a counterclockwise transmission line 4 and a clockwise transmission line 4. One of nodes 10i, for example, the node 10n is defined as the switch node, and repeat of a signal from above is inhibited normally in the switch node. If data frames received by the switch node 10n in both directions within a certain time do not coincide with each other, lines are judged to be abnormal and repeat of the signal is started. Thus, system functions are maintained to prevent the complete stop of the system, and the abnormal position is located easily to quickly perform the abnormality processing.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Field of Application) The present invention provides a method for cascading a plurality of control devices in a ring shape via a transmission path to mutually transmit data.
The present invention relates to a data transmission device that reconfigures a system so that a complete failure does not occur when an abnormality occurs in a part of a transmission path or a control device.

(Prior Art) Regarding media access control that controls the allocation of transmission paths for data transmission equipment that performs time-division data transmission, I
Various standardization efforts are underway at the EEE Society and ISO.

Especially IEEE802.4 committee and ISODP882
The token passing bus method promoted in 4 uses a media access control method that ensures transmission within a certain fixed time, so it is beginning to be adopted as a standard for control transmission equipment on factory floors. .

In the token passing bus method, only a control device (node) that holds a token with a designated transmission right can transmit data, and by passing a frame representing the transmission right to each node in turn, it is possible to send data to each node. Grant transmission rights sequentially.

Each node transmits a data frame to be transmitted within a time allotted to each node within a preset token circulation time.

Therefore, each node has a deterministic media access control method that always completes transmission within a predictable time.

FIG. 6 shows a general system configuration of the token passing bus method.

In FIG. 6, each node 10. -1o, and 1o,
,+.

10n are connected in a multi-drop manner to common transmission paths L1 and L1, respectively, to form a bus type (broadcast system) transmission system.

L2 is coupled by repeater 20 to nodes 1o, ~
lOn is now able to function as one system.

In the token passing bus method, media access is controlled by receiving and passing token frames between each node, so it is logically equivalent to a logical ring in which each node is connected in a ring shape. , Gara 1o.

The receiver is passed to 10, . . . , 10n in order, and returns to 101 again.

Each node monitors the receiving and passing of token frames, and when the system is running, the node to which the token frame was received and passed receives the token frame, and the node that received the token frame monitors the status of the sending node and detects the loss of the token. Receiving a token frame reconfigures the logical ring for passing.

In addition, when the system needs to be restarted at system start-up or due to a redundant bus failure resulting in multiple token frames, a no-signal detection timer and contention processing using a sorting algorithm regarding the node address assigned to each node are used to restart the system. Configure a healthy logical ring.

Furthermore, in the token passing bus system, the types and formats of frames exchanged between nodes are defined, and the general format of frames is as shown in FIG.

That is, as shown in Fig. 7, the frame includes PREAMBLE, which is a pattern sent to set the modem clock and level of the receiving section, start delimiter SD, frame control 1" C1, destination address DA, and source address S.
A, an information section DATA-UNIT, a frame check sequence FC8, and an end delimiter ED.

Also, Figure 8 shows an abort frame.

SD is the start delimiter, ED is the end delimiter,
This is used to terminate frame transmission midway.

That is, an abort frame is transmitted by a node that does not wish to continue the frame that started transmission, and is inserted by a repeater when it receives an invalid code sequence.

IEEE802 on token passing bus system
- According to the regulation 4, an effective frame is a portion sandwiched between a start delimiter SD and an end delimiter ED that have a signal pattern that can be distinguished from data.

As mentioned above, the token passing bus type transmission device specified by IEEE802.4 has a bus-type system configuration, and therefore, is implemented using electrical transmission/reception (one circuit and coaxial cable).

It is technically possible to use an optical fiber cable as a transmission path, but in this case an optical star coupler with a mixing function is required, and the cost is higher than that of a pure electric coaxial cable. Become.

In addition, when using an optical star coupler, it is necessary to match the optical power level of the optical receiving circuit, and in order to receive optical input from nodes at different distances, an optical receiver with a wide input sensitivity and an a*w1 range of optical output are required. A wide optical transmitter is required, and as the number of nodes increases, the cost of the optical equipment also increases, leading to an increase in the cost of the system.

The method shown in FIG. 9 is an inexpensive and highly scalable method for controlling transmission paths without changing the media access control method specified by IEEE802.4.

Each node 10□~10n using one-to-one opposing optical transceiver
There is a method of interconnecting them in cascade via optical transmission paths.

However, with this method, data sent from each node is received and repeated in order by adjacent nodes before being transmitted to all nodes, so it is possible for one node to malfunction or stop, or for a disconnection to occur at one point on the transmission path. When this happens, the entire function stops.

Also, in this method, the data sent by one node is
Since data is received from the opposite side of the transmitting node after going around the ring-shaped transmission path, each node must control the erasure of its own transmitted data that returns from the opposite side.
The inherent property of the bus-type transmission line of the 802.4 token passing system is that the data transmission node only needs to emit the transmission output unilaterally, and the output signal propagates along the transmission line toward the end point. However, it is not possible to receive the signal at each node and terminate it at the end point.

(Problems to be Solved by the Invention) The present invention involves cascading a plurality of control devices in a ring shape via a transmission path to mutually transmit data, and
When an abnormality occurs in a part of the transmission line or control device, the system is reconfigured to avoid a complete outage, and in particular, the original method of data transmission using the IEEE802.4 standard media access control method is changed to optical star. The object of the present invention is to provide an inexpensive and highly expandable data transmission device that can be realized without using expensive optical components such as couplers.

[Structure of the invention]

(Means and operations for solving the problem) FIG. 1 is a basic system configuration diagram of the present invention, in which each node 10□ to 1
0n can be received from both left and right directions, and can be replayed in both left and right directions, and two sets of transmission paths L1.0n are provided in both left and right directions. L.

cascaded in a ring through node 1
At least one of 01 to lOn (10n in Figure 1) does not always repeat in either the left or right direction, and is switched so that it can repeat in both the left and right directions only when one other node is abnormal. It is configured as a switch node.

FIG. 2 shows the basic configuration of each node 10 including switch nodes, in which 11 is a media access control unit that executes a media access control function, 12 is a media access control unit that performs data communication using a transmission function, and provides various services. A node control unit 13 that controls functions is a modem, and an interface signal 3 is connected between the modem 13 and the media access control unit 11.
interconnected by 0.

A switch node can be realized by partially changing the modem circuit settings of a normal node, and has the function of determining whether or not the same frame is received from both directions within a preset period of time. This detects abnormalities in other nodes or transmission lines and performs switch operations such as canceling repeat prohibition.

In other words, in FIG. 1, the switch node 10n is always
does not perform a repeat operation, therefore, the transmission line L1gL is terminated by the switch node LOn, and the transmission line L1gL is terminated by the switch node LOn.
~10n-, performs the same transmission operation as in the case of the bus system.

That is, at all times, the switch node 10n receives the same frame from the left and right sides within a preset period of time that is greater than the maximum time difference received through the left transmission path L□ and the right transmission path. If a disconnection or abnormality occurs in a part of the node and data transmission is interrupted, the same frame is not received from both directions within the above-mentioned fixed time, so the switch node 10n determines this and prohibits its own repeat. At the same time, an abort frame is sent in both directions.

Normal nodes other than switch nodes 10. ~10,1, when receiving an abort frame, repeats the abort frame, and determines whether the other receiving fd unit has also received an abort frame (B), and transmits check pattern data according to the determination result to the abort frame. This identifies the abnormal location, stops repeating the node in question, and reconfigures the system using this node as a terminal station.

FIG. 3 shows an abort frame format with the above-mentioned check pattern CHECK added. For example, when an abort frame is received from both sides, the check pattern is set to 1.
111, and when an abort frame is received only from one side, the check pattern is set to ``''01.

FIG. 4 shows node 10. This shows the occurrence of an abort frame when the leftward transmission path between node 10. and node 10□ is disconnected. receives the 7-boat frame only from the rightward transmission path, so it repeats AB·0 in the rightward direction and does not repeat in the leftward direction.

Node 10. repeats AB・1 because abort frames are input from both the left and right directions. Thereafter, the abort frame is repeated in the same manner as shown in FIG.

Since each node is configured to stop its repeat function upon receiving the AB-0 7-vote frame, nodes 101.10. stops its repeat operation and functions as an end station of the transmission path, and the switch node becomes capable of repeating and stops transmitting abort frames. As a result, the transmission system is reconfigured, and nodes to1. to.

System functionality is maintained even if the transmission line between the two is disconnected.

(Embodiment) FIG. 5 shows an embodiment of the circuit configuration of the modem 13 of the node 10 used in the present invention.

In FIG. 5, the rightward and leftward transmission paths,
The received signals from L, respectively, are sent to the receiver (R1゜R,)
56 and 57 to the reception control circuit (RVCTl).

The received data is reproduced at 3t86.87 at RVCT, ) 52.53, and the frame coincidence detection circuit (FCIN) 42 outputs the abort frame detection time M (ABD'l', ABDT,
)44°45, check pattern detection circuit (CHDT,
.

CHD T, ) 47, 49, and receive (Ftill selection circuit (
FR8L) to the transmission repeat control circuit (SRCTl, 5RCT, ) via the exclusive OR circuit 61.60
It is input to 54 and 51.

Some transmission data from the media access control unit 11 (T
DT), a transmission clock (TCLK), and a transmission start/stop timing signal (TST/TSP).
) 40, and its output is input to the OR circuits 62 and 63 as the transmission data signal 83, and is also input to the transmission repeat control circuit (SRCT).

S RCT > 54.51 is input.

Therefore, the transmission data signal 83 is ORed with the reception data signal 86.87 in the OR circuits 62.63, respectively, to obtain reception data 92.93, which is sent to the reception data (RDT) and reception clock (RCLK) via the FR8L43.

The media access control unit 11 receives the received data signal 91 including the reception start/stop timing signal (R5T/R8P).
is input.

64 is a switch node function designation switch, which becomes a switch node by opening this switch.

65 is a monitoring time setting switch determined by the total length of the system, and if the FCI N42 does not detect received data of the same frame from the left and right sides within this set time, an abort transmission condition (ff number 84) is generated, and the abort sequence control circuit ( ABSQ) 41 and repeat prohibition release signal 8
5 and an abort frame transmission start signal 82.
The abort pattern generation circuit (ABPG) 40
Accordingly, the ABPG 40 generates abort frame data 81 and inputs it to the OR circuit 59.

As a result, the abort frame is transmitted in both left and right directions via the transmission repeat control circuits 51 and 54.

When the switch node function designation switch 64 is closed and designated as a general node, the non-switch node condition signal 9o is outputted via the inverter circuit 66 to ABDT144. ABD
T, 45. CHDT□47° is input to CHDT, 49 and switch control circuit (SWCT) 50.

In this state, abort frames are received from the transmission paths in both directions, and the abort frame detection circuit ABDT144. ABD
When T□45 detects an abort frame, detection output 9
4. ! J7 and 95.06 are check pattern generation circuits (CHPG, respectively).

CHPG, ) 46, 4g, and when both detect an abort frame, a check pattern of ``1'' is generated, and when only one detects an abort frame, a check pattern of 10'' is generated.

5WCT50 is non-switch node condition 90, FCIN4 indicating that the same frame is not received from both directions.
frame mismatch output signal 88 of 2, and CHDT, 4
7. Check detection signal 70.71 from CHDT, 49
is input, it is determined whether the check pattern 111 is being received from both directions, or whether one is 10', and if the left direction reception input is 101, the right side transmission/reception prohibition signal 73 is activated, and the right direction reception input is %0', the left side transmission/reception prohibition signal 72 is activated to prohibit right side transmission/reception or left side transmission/reception, respectively.

As a result, the node in question is logically disconnected from the node adjacent to the right or left side, and the switch restores the repeat function, allowing the node to function as the end station of the bus-type transmission path. The transmission system is reconfigured and data transmission resumes.

In FIG. 5, the transmission line L1. L, is used as an optical fiber to transmit an optical signal, and the amount of light is 0'tll156.57
Although optical/electrical conversion is performed using optical transmitters 55 and 58, it is also possible to directly transmit electrical signals without using optical signals; in this case, the earthenware optical receiver 56
, 5 and the optical transmitter 55.5Jl can be omitted.

(Effects of the Invention) As explained above, according to the present invention, a plurality of nodes including a switch node are cascade-connected in a ring shape via a pair of transmission paths that transmit data in opposite directions, and the repeat of the switch nodes is normally connected. When data transmission is interrupted due to an abnormality or disconnection in a normal node or transmission line, the switch node detects this and starts repeating. Therefore, system functionality is maintained and complete system shutdown is prevented.

In addition, since a transmission system can be configured through cascade connections, optical transmission using optical fibers is easy, and an expensive optical star coupler with a mixing function, which is required in the case of the conventional bus type, is not required, making optical transmission economical. It is possible and
In particular, it is possible to economically realize an optical transmission system compatible with a token passing bus type transmission device specified by IEEE802.4.

Further, in the present invention, since the node where the abnormality is detected becomes the end station of the bus-type transmission line, the abnormality can be easily identified and the abnormality can be quickly processed.

[Brief explanation of drawings]

Figure 1 is a system diagram showing the basic configuration of the present invention, Figure 2 is a diagram showing the configuration of each node used in the present invention, and Figure 3 is the format of an abort frame with a check pattern used in the present invention. 4 is a diagram showing an example of the abort frame rate state in the present invention, FIG. 5 is a circuit diagram showing an embodiment of the modem in FIG. 2, and FIG.
The figure shows the general configuration of a bus-based transmission system.
FIG. 7 is a data frame format diagram, FIG. 8 is a data frame format diagram, and FIG. 9 is a system diagram showing an example of a conventional indigenous transmission device. 10, ~10rl... Node 11... Media access control unit 12... Node control unit 13... Modem 40...
・Abort pattern generation circuit (ABPG) 41...Abort sequence control circuit (ABSQ) 42...
・Frame coincidence detection circuit (FCIN) 43...Reception selection circuit (FR8L) 44.45...Abort frame detection circuit (ABDT)
,,ABDT,) 46, 48...Check pattern generation circuit (CHPG
1, CHPG, ) 47, 49... Check pattern detection circuit (CHDT, CHDT,) 50... Switch control circuit (SWCT) 51.54.
...Transmission repeat control circuit (SRCT, 5RCT,) 52, 53-...Reception control circuit (RV CT, ,R
V CT, ) 55, 58... Optical transmitter 56.57
... Optical receiver 64 ... Switch node function designation switch 65 ... Monitoring time setting switch Agent Patent attorney Yoshiaki Inomata (and one other person) Figure 1 Figure 2 Figure 4 -

Claims (6)

[Claims] (1) Multiple nodes that can send and receive data in both directions and repeat data in both directions are cascaded in a ring shape via a pair of transmission paths that transmit data in opposite directions, and then The data transmission device is characterized in that at least one node of the data transmission device is configured as a switch node that normally prohibits repeating and starts repeating when data frames received from both directions within a certain period of time are not the same. (2) A patent in which the switch node is provided with a frame coincidence detection circuit that cancels the repeat prohibition of the switch node and sends an abort frame to another node when the data frames received from both directions within the certain period of time are not the same. A data transmission device according to claim 1. (3) The data transmission device according to claim 1, wherein the switch node is configured with the same circuit as the other nodes, and the switch function is given by changing the circuit settings. (4) The above-mentioned pair of transmission lines are constructed of optical fiber cables, and each node including a switch node is provided with an optical receiver and an optical transmitter for performing optical/electrical conversion at the receiving end and the transmitting end, respectively. The data transmission device according to item 1. (5) When each node receives an abort frame, it determines whether or not it has also received an abort frame from the receiving end on the opposite side, and applies a check pattern indicating the determination result to the abort frame. 2. The data transmission device according to claim 1, further comprising a check pattern generation circuit for additionally transmitting a check pattern. (6) A claim that prohibits a node that has received an abort frame with a check pattern indicating that the abort frame is received from only one side from transmitting and receiving the abort frame on the side that received the abort frame. The data transmission device according to item 5.