JPH06164611A - Communication system for ring type local area network - Google Patents

Abstract

PURPOSE:To provide a communication system for a ring type local area network which can simplify its constitution and the signal processing and unnecessitates assignment of addresses to the terminal units. CONSTITUTION:A master unit M and the terminal units CH1-CH60 are successively connected with a ring type transmission line L in a transmission/reception enable way. These units M and CH1-CH60 successively transmit and receive the frames where plural blocks of the same bit length are connected in time sequence. Then the master unit M sets the address flag of each block, and each of units CH1-CH60 resets the address flag of the head block having its set address flag and then reads and writes the input/output data on the head block as its own data.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ring type local area network communication system.

[0002]

2. Description of the Related Art Conventionally, a bus type or ring (loop) type local area network (LAN) is often used. In the conventional ring type LAN, the token ring system described below is mainly used. That is, in this token ring system, a token including a flag indicating that writing is not possible circulates around the ring transmission line, and each terminal unit can only write when the flag of the received token indicates that writing is possible (token empty). After that, a frame consisting of the self address, the other party (transmission destination) address, and the data is written and transmitted to the next terminal unit.

[0003]

However, in the above-mentioned conventional token ring system, an address must be set for each terminal unit, and further, when writing and transmitting data, the self address and the partner address are combined. However, there is a problem in that the system configuration and system startup work become complicated.

In particular, each device connected to each terminal unit of the LAN operates by a simple start / stop command from the master unit, and each device operates / stops itself or operates normally / stops.
In the case of a simple device control configuration in which only an abnormal status display is transmitted to the master unit, the token ring method as described above is too complicated compared to the configuration of each of these devices, and L
It offsets the effectiveness of AN.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide a ring-type local area network communication system having a simple system configuration, high reliability, and simple system startup work. , Its purpose is.

[0006]

A communication system of a ring type local area network according to the present invention comprises a master unit and a plurality of terminal units each having a communication function, which are connected to each other on a ring-shaped transmission line to which transmission and reception can be sequentially performed. A ring-type local area network communication method for performing communication between the master unit and each of the terminal units by circulating a frame in which a plurality of blocks of equal bit length are sequentially connected in sequence, In the Nth block of the master unit on the transmission line, the input data to be communicated between the Nth terminal unit and the master unit, the output data, and the control flag are respectively placed in the same bit position. The control flag carries an address flag indicating the address of each terminal unit. The master unit sets the address flag of each block and reads / writes the input data and output data of each block in the order of connection of the terminal units, and the terminal units set the address flags. The address flag of the leading block in the state is reset, and the input data and output data of the leading block are read / written as their own data.

In a preferred mode, the control flag includes a write flag indicating a write status of each terminal unit, each terminal unit writes its own data as input data to its own block and sets the write flag, The master unit resets the write flag of the block that has read the input data. In a preferred aspect, the control flag includes an off-line flag indicating whether or not the terminal unit is writable, and the master unit is in a block corresponding to the predetermined terminal unit when the communication with the predetermined terminal unit is cut off. The offline flag is set and each terminal unit stops reading / writing of the input / output data in the self block when the offline flag in the self block is set.

In a preferred mode, the control flag includes a reception error flag which indicates the presence or absence of a reception error of each terminal unit, and when each terminal unit cannot receive next time within a predetermined allowable time from the time of previous reception. Send the reception error flag. In a preferred mode, when the master unit receives the reception error flag, the master unit retransmits a frame transmitted previously a predetermined number of times without writing it.

In a preferred mode, the terminal unit resets the reception error flag in the self block when the output data of the self block in the retransmission frame is normally read. In a preferred aspect, the allowable time of each block is configured by adding a different additional waiting time to each frame 1 round time.

[0010]

The ring-type local area network is composed of a master unit and a plurality of terminal units each having a communication function, which can be sequentially transmitted and received through a ring-shaped transmission line. The master unit and each terminal unit sequentially transmit and receive a frame in which a plurality of blocks each having the same bit length are connected in time-sequential order through this transmission path.

The Nth block of the frame stores the input data, the output data and the control flag, which are to be communicated between the master unit and the Nth terminal unit and the master unit on the transmission line, in the same bit position. Carried, the control flag includes an address flag indicating the address of each terminal unit. The master unit sets the address flag of each block and reads / writes the input data and output data of each block in the connection order of each terminal unit (counted from the master unit on the transmission path). Each terminal unit resets the address flag of the head block in which the address flag is set, and further reads / writes the input data and output data of this head block as its own data.

That is, in this embodiment, each block corresponding to each terminal unit circulating on the transmission line is arranged into a frame in the order of connection of the terminal units counted from the master unit on the transmission line, and a predetermined bit of each block is further arranged. An address flag is provided at the position. Here, the master unit sets all address flags of each block and reads / writes input data and output data of each block.

Then, the first terminal unit in the traveling direction from the master unit as a starting point reads / writes the input data and the output data of the first block (self block for the first terminal unit) in the frame. Then, the Nth terminal unit in the above direction reads / writes the input data and the output data of the Nth block (self block for the first terminal unit) in the frame. Particularly in the present invention, each terminal unit resets the address flag in its own block. As a result, as the frame passes through each terminal unit, the address flags of each block are sequentially reset from the first block. After all, it is understood that the terminal units in an arbitrary order may read / write the first (head) block in which the address flag is set as the self block from the received frame.

[0014]

As described above, in the communication system of the ring type local area network of the present invention, blocks for individually storing data and control flags of each terminal unit are arranged sequentially in the order of connection of each terminal unit. Form a new frame (block train), circulate on the transmission path, and each terminal unit recognizes the first block with an address flag of 1 as its own block, and resets the address flag of its own block to the next terminal. It uses a ring-type local area network configuration that transmits to the unit.

With this configuration, it is not necessary to set the address of each terminal unit one by one, the change on the way is simple, and it is not necessary to write the self address and the partner address together with the data when transmitting the data. It is possible to realize a local area network communication method that is simple in configuration and data processing and easy to start up the system.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a communication system of a ring type local area network of the present invention will be described below with reference to the drawings. This ring-type local area network includes a master unit M and 60 terminal units CH1 to CH.
A ring-type local area network is configured by connecting the respective transmitting terminals S and receiving terminals R of 60 by serial transmission lines L.

Master unit M and terminal unit CH
1 has an 8-bit microcomputer, and the transmitting terminal S and the receiving terminal R are I / O of these microcomputers.
Configuring the interface. Furthermore, the I / O interface of the master unit M is the keyboard K, CR
It is connected to the T display device C and has a transmission terminal and a reception terminal for the upper LAN.

I / O of each terminal unit CH1 to CH60
The interface has two pairs of input terminals and two pairs of output terminals for pair cables, respectively, and the above two pairs of input terminals of the terminal units CH1 to CH60 are individually connected to the two pairs of output terminals of each automatic machine 1 to 60. The two pairs of output terminals of the terminal units CH1 to CH60 are individually connected to the two pairs of input terminals of the automatic machines M1 to M60.

In each of the automatic machines M1 to M60, the first output terminal is a terminal which outputs a non-defective signal A which indicates its normal state, and the second output terminal is a signal B which indicates an abnormal state of the input self. The first input terminal is a terminal that receives the start command C, and the second input terminal is a terminal that receives the stop command D. Of course, even if the normal state / defective state is displayed by the first output terminal of each of the automatic machines M1 to M60, and other signals such as the output timing of the non-defective signal A are displayed by the second output terminal. Good.

That is, each of the automatic machines M1 to M60 is a relatively simple device and receives a 2-bit operation command (output data) and outputs a 2-bit status display (input data). Of course, the above 4-bit input / output data is set to 1
It is of course possible to divide the data into bits + 3 bits. FIG. 2 shows the structure of an information group (frame) circulating in this ring LAN.

One frame consists of a 64-bit sequential bit string, STX consisting of the first 2 bytes is the head byte indicating the start of the frame, and ETX consisting of the last 2 bytes is the tail byte indicating the end of the frame.
The 3rd byte to the 62nd byte of the frame respectively form the 1st to 60th blocks. The first block includes input / output data A to D of the terminal unit CH1, and the Nth block includes input / output data A to D of the Nth terminal unit CHN. Therefore, in FIG.
The block is given the same code CH1 as the terminal unit CH1, and the 60th block is given the same code CH60 as the terminal unit CH60.

FIG. 3 shows the bit structure of an arbitrary block. Each block is composed of 8 bits, and is composed of an address flag, an offline flag, a reception error flag, a terminal write flag, an input data A, an input data B, an output data C, and an output data D in order from the upper bit. . What is important here is that each terminal unit CH1 to CH
60 is to read / write the input / output data A to D only in its own block. In other words, the Nth terminal unit CHN counting from the master unit M is
The master unit M reads / writes the input / output data A to D of the Nth block CHN in the frame, and the master unit M inputs / outputs data A to D of the Nth block CHN in the frame.
The point is to read / write D as the Nth terminal unit CHN.

The operation of this ring type LAN will be described below. First, the operation of the master unit M will be described with reference to FIGS. However, here, the terminal unit CH1
It is assumed that CH60 is in operation. When the power is turned on, initialization is performed (100), and an offline flag process is first performed (102). This off-line flag processing checks whether or not there is a terminal unit which is instructed in advance by the keyboard K not to receive the input data (command to the automatic machine) A and B, and if there is, it should be transmitted next (here. Then, the process of setting the off-line flag of the block corresponding to the terminal unit in the (first) frame.

Next, the input data A and B to be written are sequentially set in the respective blocks of the frame to be transmitted, and the output data (the status display of each automatic machine) C to D to be read are read. Since it is the first time here, the output data to be read is 0. Further, the address flags of all blocks in the frame to be transmitted are set, the write flags are reset (104), and transmission is performed (10
6).

Next, it is checked whether or not the reception processing operation is completed (whether or not a reception end flag, which will be described later, is set) (108), and if not completed, it is checked whether or not the built-in timer is over (110). Here, the built-in timer operates from the end of the previous transmission, and the delay time Tm is set. The above reception processing operation is processed by the interrupt routine of FIG. 5, which interrupt routine operates by STX reception from the terminal unit CH60, performs reception processing of each subsequent block, and sets a reception end flag by ETX reception (200 ), Return to the main routine.

The delay time Tm of the built-in timer is set to 71 seconds, which is the maximum frame round-trip time Tc (10 seconds in this case) plus a predetermined time ΔT (61 seconds in this case). If the time is over in step 110, step 11
Proceed to step 2 to perform alarm processing (112), and the routine ends. The alarm processing subroutine in this case refers to processing for transmitting a flag indicating poor reception from the terminal unit CH60 to the upper LAN and displaying it on the CRT display device C.

If the time is not over in step 110, the process returns to step 108 to wait for the reception completion, and if the reception is completed, the reception end flag is set,
It is checked whether the reception error flag is set in the reception frame (114). If the reception error flag is set, the number of retransmissions S is a predetermined value (here, 2
(116), and if not, reset the previously transmitted frame to the register for transmission without processing (118), add 1 to the number of retransmissions S (120), It is transmitted (106).

If the number S of retransmissions exceeds the predetermined value (two times in this case) in step 116, the process proceeds to step 112, alarm processing is performed, and the routine ends. The alarm processing subroutine in this case refers to processing of transmitting the address of the terminal unit corresponding to the block including the reception error flag and the flag indicating the reception failure to the upper LAN, and displaying the reception failure on the CRT display device C. .

Next, the operation of each of the terminal units CH1 to CH60 will be described with reference to the flowchart of FIG. When the power is turned on, initialization is performed (300), and it is checked whether the reception processing operation is completed (whether a reception end flag described later is set) (302). If not completed, an automatic machine managed by itself is used. Read / write data between (3
03), and then it checks whether the built-in timer is over (304). Here, the built-in timer operates from the time when the previous transmission is completed, and the delay time Tn (n = 1 to 60) is set.

The above reception processing operation is processed by an interrupt routine (not shown) similar to the interrupt routine of FIG. 5, and this interrupt routine operates by the STX reception from the immediately preceding terminal unit CHn-1, and the subsequent blocks are processed. Reception processing is performed, a reception end flag is output by ETX reception (200), and the process returns to the main routine. The delay time Tm of the built-in timer is a value 10 + n obtained by adding a predetermined time ΔT (here, (1 × the number n of the terminal units CH1 to CH60) seconds) to the maximum frame round trip time Tc (here, 10 seconds).
Set to seconds. For example, the delay time of the terminal unit CH10 is set to 20 seconds.

If the time is over in step 304, the flow advances to step 306 to create a frame in which the reception error flag of the own block is set (a frame with a reception error flag), and the process advances to step 318 to generate this frame with a reception error flag. Send. The address flags of the self block of the frame with the reception error flag and the blocks upstream thereof are reset.

On the other hand, if the time is not over in step 304, the process returns to step 302 to wait for the reception completion, and if the reception is completed, the address flag and the reception error flag in the self block of the reception frame are reset (308). Check 310 if the offline flag is set. If the off-line flag is set, the process proceeds to step 318 and the input / output data A to D of the received frame is transmitted without change. If the off-line flag is not set, the self-blocking of the received frame (that is, the frame) is performed. The output data C and D of the first block in which the address flag is set) are read, and the input data A and B are written. More specifically, these input / output data A to D are set in the own transmission buffer memory (312). In this specification, read means transfer from the storage area holding the received frame to its own output data C and D storage areas. Further, in step 312, the write is a process of rewriting the data of the input data A and B of its own block, that is, when the input data A or B is 0, 1 is set, and when the input data A or B is 1, it is reset to 0. When you do.

Next, in step 312, it is checked whether or not the write (rewrite) is performed (314). If not, the process proceeds to 318 to transmit the frame, and if it is performed, the write flag is set. , Frame is transmitted (318). Next, the built-in timer is restarted and the process proceeds to step 302 to prepare for the next reception completion.

The operation and effect of the above embodiment will be described below. (A) First, in this embodiment, the input / output data of each terminal unit is circulated as a sequentially continuous frame, and the address for identifying the block of each terminal unit is composed of a 1-bit address flag. Then, the master unit sets the address flags of all blocks, and each terminal unit resets the address flag of the leading block whose address flag is set, and identifies this leading block as its own block. .

As a result, all terminal units CH1 to CH6
In the case of 0, it is not necessary to set the self address and the destination address for transmission as in the conventional case, and the LA has a very simple circuit configuration and processing operation of the terminal units CH1 to CH60.
N can be configured. (B) Next, since the terminal unit includes a write flag indicating the writing (rewriting) of its own data (input data A, B), the master unit can easily identify the state change of each automatic machine, and , If the write flag can be normally transmitted even if the input data A and B are erroneously transmitted, the master unit is irrespective of the erroneous transmission of the input data A and B.
There is no false detection.

(C) Next, since each block has an offline flag for instructing the write inhibition of the terminal unit,
The input data A and B of the terminal unit that the master unit does not want to communicate with will not be rewritten. (D) Each block includes a reception error flag indicating whether or not there is a reception error in the terminal unit, and each terminal unit has a predetermined permissible time exceeding one frame round-trip time from the last frame reception time (or transmission time). If the next frame cannot be received even after the time elapses, the master unit sends a reception error display frame with the reception error flag of its own block set, so the master unit can easily determine which terminal unit is in a bad transmission state. Can be identified and displayed.

(E) When the master unit receives the reception error flag, it retransmits the previously transmitted frame a predetermined number of times without writing it. Therefore, due to some temporary transmission failure or the like on the transmission line or a specific terminal unit. When a communication failure occurs and is then restored, the communication can be restored normally. Naturally, the terminal unit resets the reception error flag in the self block when the output data of the self block in the retransmission frame is normally read.

(F) An arbitrary terminal unit n receives a frame with a reception error flag (reception error display frame) transmitted by all the terminal units downstream and upstream of itself from the terminal unit in which the transmission failure has occurred, and The delay time is set so that the frame with its own reception error flag is transmitted after the frame is transmitted downstream. In this way, transmission processing and reception processing do not overlap at any terminal unit, and signal processing becomes simple.

The following modifications are possible in the communication system of the ring type local area network of the present embodiment described above. That is, it is possible for one terminal unit to occupy a plurality of consecutive blocks (for example, two blocks). In this way, a 1-byte block can be allocated to a simple automatic machine, and a plurality of blocks can be allocated to an automatic machine that requires complicated data exchange.

In this case, various composite block configurations are possible. The simplest example is that one terminal unit uses the bits of specified input / output data A to D of a plurality of consecutive blocks. Therefore, in this case, the prescribed input / output data bits (4 bits in the first embodiment) of the number of consecutive blocks used by one terminal unit × 1 block are data bits.

What is important here is that this terminal unit resets all the address flags of a plurality of consecutive blocks used by itself and transmits them to the next terminal unit. Since each of the other flags needs only one bit, the bit positions of the remaining blocks of the continuous plurality of blocks except the first block can be diverted to data bits.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of a communication system of a ring type local area network of the present invention.

FIG. 2 is a byte configuration diagram of a cyclic frame.

3 is a bit configuration diagram of the block of FIG. 2. FIG.

FIG. 4 is a flowchart showing the operation of the master unit shown in FIG.

5 is a flowchart showing the operation of the master unit of FIG.

6 is a flowchart showing the operation of the terminal unit of FIG.

[Explanation of symbols]

 M master unit CH1 to CH60 terminal unit

Claims (7)

[Claims] 1. A frame in which a plurality of blocks each having the same bit length are time-sequentially connected to each other on a ring-shaped transmission path to which a master unit and a plurality of terminal units each having a communication function are sequentially connected so that they can be transmitted and received. In the communication method of a ring-type local area network for performing communication between the master unit and each of the terminal units, the N-th block of a frame is the first from the master unit on the transmission path. Input data, output data, and a control flag to be communicated between the Nth terminal unit and the master unit are carried in the same bit position, and the control flag is an address indicating the address of each terminal unit. Flag, the master unit sets the address flag of each block In addition, the input data and the output data of each block are read / written in the order of connection of the terminal units, and each terminal unit resets the address flag of the leading block whose address flag is set and A ring-type local area network communication method that reads / writes the input data and output data of the above as its own data. 2. The control flag includes a write flag indicating a writing status of each terminal unit, each terminal unit writes its own data as input data to its own block and sets the write flag, and the master unit sets The communication system of a ring type local area network according to claim 1, wherein the write flag of a block that has read input data is reset. 3. The control flag includes an off-line flag indicating whether or not the terminal unit can be written, and the master unit is in a block corresponding to the predetermined terminal unit when the communication with the predetermined terminal unit is cut off. 2. The ring type local area network according to claim 1, wherein the offline flag of the ring type local area network is set, and each terminal unit stops read / write of input / output data in its own block when the offline flag in its own block is set. Communication method. 4. The control flag includes a reception error flag indicating whether or not there is a reception error in each terminal unit, and each terminal unit has passed a predetermined allowable time exceeding one frame round time from the time of the last frame reception. 2. The ring-type local area network communication system according to claim 1, wherein a reception error display frame in which the reception error flag of its own block is set is sent out even if the next frame reception cannot be performed. 5. The ring-type local area network communication system according to claim 4, wherein said master unit retransmits a previously transmitted frame a predetermined number of times when receiving the reception error flag without writing the frame. 6. The ring type local area network according to claim 5, wherein the terminal unit resets a reception error flag in its own block when the output data of its own block in the retransmitted frame is normally read. Communication method. 7. The N (N> 2) th terminal unit, which is counted downstream from the faulty terminal unit having a fault in frame transmission, is downstream from the faulty terminal unit and more than the Nth terminal unit. The communication system of the ring type local area network according to claim 4, wherein after transmitting the reception error display frame transmitted by each upstream terminal unit, the reception error display frame of itself is transmitted.