JPS60220640A - Information communication system - Google Patents

Abstract

PURPOSE:To make sure retransmission possible by providing a means, which detects contravention of a rule of the transmission code encoded to a certain standard to detect collision between nodes, in each of plural nodes sharing a transmission line and using the transmission line preferentially for retransmission. CONSTITUTION:Each node 1 is provided with a carrier detecting part 12, to which a reception signal 18 from the transmission line is inputted to detect the use state of the transmission line, and a collision detecting part 13' to which the signal 18 is inputted to detect whether transmissions collide against each other or not. In this case, the Manchester code where the signal level is inverterd in the center of a bit is used as the code rule of a binary digital signal to be transmitted. If transmissions from two nodes occur on the transmission line and collide against each other, the detecting part 13' detects contravention of the code rule from the signal 18 and outputs a collision detection signal 19 because the code on the transmission line contravenes this rule. Stations where new transmission requests occur are supended transmitting them at the collision detection time until transmission information from transmission and reception stations which coolide against each other before are retransmitted completely, thereby avoiding collision at the retransmission time.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to an information communication system, and in particular to an information communication system in which transmission path resources are shared between a plurality of information processing devices and packet communication is performed using Manchester codes. Regarding the system.

[Background of the invention]

This type of information system attempts to economize transmission resources by sharing transmission path resources by organically interconnecting locally distributed information processing devices.

FIG. 1 is a system diagram showing an example of a transmission line network used in this type of information communication system.

In FIG. 1, the transmission line network includes nodes It l 12 + Ig + . . . which are communication control devices (transmission/reception stations).
.

1, and each node 11 * 1ml 13 + ""
It consists of a transmission line 2 to which HIm are commonly and equally connected, and a terminating resistor 3 provided at the end of the transmission line.

FIG. 2 is a block diagram showing the internal configuration of node 1.

In the figure, node 1 includes a processor 4 that performs internal processing, and a DMA control unit 5 that directly accesses memory during transmission and reception.
and a memory 6 for storing various data and programs.
, an internal bus 7, an external interface unit 8 for connecting with external information processing equipment, a path buffer 9 for temporarily storing transmitted and received data, and a serial/parallel conversion unit 10 for serial/parallel conversion of transmitted and received data. and the serial/parallel converter 10
The network transmission signal 1 is encoded by encoding the transmission data from
At the same time, a code converter 11 takes in the network reception signal 18 and decodes it, a carrier detector 12 detects the carrier on the transmission path 2, and detects that a collision has occurred on the transmission path 2. collision detection signal 19
and a collision detection section 13 that outputs.

An example of the configuration of the collision detection section 13 used in the node 1 is shown in FIG.

In FIG. 3, the collision detection circuit 13 performs a delay 16 that temporally matches the network transmission signal 17 with the network reception signal 18, and an exclusive OR operation that compares the comparison reference signal 20 obtained by the delay 16 with the network reception signal 18. It consists of a circuit 15 and a flip/70 tube 14 that latches the comparison result.

The operation of the information communication system including the node 1 configured in this way will be explained with reference to FIGS. 1 to 5.

FIG. 4 is a time chart shown to explain the operation of the collision detection section 13 shown in FIG. 3. FIG. 5 is a time chart showing a retransmission procedure when a collision occurs in the information communication system.

First, the general operation of the above information communication system will be explained.

A certain node 1. When transmitting data, the carrier detecting section 12 confirms that there is no carrier on the transmission path 2, and then transmits the data. When the collision detection unit 13 detects a collision with a transmission from another node 1, generally the node 1. is for retransmission.

Here, the operation of detecting a collision by the collision detection section 13 will be explained.

During normal operation, that is, during the period TI shown in FIG. 4, the comparison reference signal 20 and the network reception signal 18 match, and the output 21 of the exclusive OR circuit 15 is "O".

Therefore, the flip/flop 14 does not operate, and the output Q1 of the clip/flop 14, that is, the collision detection signal 1
9 becomes 0''.

When an abnormality occurs, that is, when a collision occurs, the comparison reference signal 20 and the network reception signal 18 do not match, and the output 21 of the exclusive OR circuit 15 becomes '1'', as shown in period T2 in FIG. This is sampled by the sampling clock 22, and the output latched by the 7-rip/four-tub 14 is output as the collision detection signal 19.

Next, an example of the transmission procedure will be explained with reference to FIG.

Each node It, 1x+1g+..., 1. When a transmission request is generated internally, the carrier detection section 12 first starts carrier sensing, and after confirming that there is no carrier on the transmission path 2, starts transmission. Now, tentatively,
Suppose that a transmission request occurs inside node II at time tl, then time t! When node II performs carrier sensing at time t2 and confirms that transmission path 2 is empty as a result of the carrier sense, node II performs carrier sensing at time 1. The text 23 is sent during this time. While node II is transmitting, when node 11 generates a transmission request internally at time t3 and node 1k generates a transmission request at time t4, both nodes IJ and It start carrier sensing, but since there is a carrier from node II, Waiting for transmission, node 1j, lh at the end point ts of text 23
Both detect carrier-off (no more carrier) and start text transmission after time t6. Naturally,
At this time t7, a collision occurs between the nodes 11 and lh.

Recognizing the occurrence of the collision, the nine nodes IJIII refer to their internal random numbers, wait for times TJI and Thl, and perform carrier sensing again at times to and tto, respectively. ζNow, if To<T+u is set, transmission path 2
Assuming that there is no carrier on the network, node IJ starts transmission after sensing the carrier and successfully retransmits it.

On the other hand, when the node lh senses the carrier after Tkx has elapsed, it detects the carrier of the node 1j, so it waits until the text 24 of the node 11 ends and carrier off is detected. During this time, when a transmission request occurs within node 1 at time ttx, node 1t also waits for carrier-off detection.

When both detect carrier-off at time ttz, they start transmitting at the same time, so a collision occurs again. in this case,
Both nodes lk and lz refer to random numbers internally, and each Tsv
+Tt, but the second retransmission is not required for node 1, and node 1's wait time Tw m (n is the number of retransmissions) is 'r,, 1. <'r,,< T,, ,,,,
・<1>Tv(II+l)1ml +1(Tw(+
＋＋su＜ Tv(n+x)wax ”°(2)Twm
max < Tw(i+ll ml+i'...(3)
Since there is generally a relationship, Ttlmaz < Tk2tm I-. Therefore, node 1 will be retransmitted after node 1t finishes retransmitting, but if another node 1 transmits during this time, node 1 will be unable to retransmit until there are no nodes that can collide with it. . Generally, retransmission is given up after a specified number of retransmission failures, so the information that was intended to be retransmitted ends up not being transmitted. As described above, since the collision detection unit 13 of each node performs collision detection by comparing the transmitted data and received data of the own node 1, collisions of the own node 1 can be detected, but collisions between other nodes can be detected. Since collisions cannot be detected, other nodes will collide with new transmissions in response to retransmissions due to collisions, and as the number of retransmissions increases, the weight also increases. There is a problem in that the transmission to the node 1 that has woken up is delayed the last time.

[Purpose of the invention]

The present invention has been made in view of the above problems, and its purpose is to provide an information communication system that prevents retransmission failures and is equipped with a highly efficient and reliable transmission network. be.

[Summary of the invention]

In order to achieve the above object, the present invention detects a violation of a transmission code code encoded in each node based on a certain rule, thereby detecting a collision between the own node and another node, and When a collision occurs between the two, priority is given to retransmission.

According to the information communication system of the present invention, retransmission can be ensured successfully and retransmission can be prevented, thereby ensuring immediacy and high efficiency of the transmission network.

[Embodiments of the invention]

Hereinafter, embodiments of the present invention will be described based on the drawings from FIG. 6 onwards. In the embodiments of the present invention, the same components as those shown in FIGS. 1 to 5 will be described with the same reference numerals.

FIG. 6 is a block diagram showing the internal configuration of each node 1f used in an embodiment of the information communication system according to the present invention. The difference between the node 1f shown in FIG. 6 and the node 1 shown in FIG. 2 is that only the received signal 18 is supplied to the collision detection unit 13, and the collision detection unit 13 is configured to detect a collision using only the received signal 18. It is in.

Next, regarding the collision detection operation at the node 1, the seventh
This will be explained using FIGS. 8 and 9.

FIG. 7 shows the transmission codes used in this embodiment.

In FIG. 7, when transmitting a binary digital signal indicating 'θ'' and '1'', according to this code convention, a pulse rises at the center of Bs, Bs, Bs,... Assume that the upper side indicates O'', and the fall of the cross indicates 9 mold 1'', and the signal level is always inverted at the center of B).

This is commonly called the Manchester code.

FIG. 8 shows the internal circuit of the collision detection section 13'.

In FIG. 8, a network reception signal is applied to the input end of DT clip/flop 24, and a signal from its output end Q is applied to the input end of DT7 rip/flop 25. The flip/flop 24.25
A clock p signal cLK, CLK is supplied to the input terminal T of the . The output signal from the output terminal Q of the clip/flop 25 is supplied to the input terminal of the shift register 29. A clock signal (CLK) 34 is input to the clock input terminal CLKK of the shift register 29 . The comparison signal 30 at the output terminal Q of the shift register 29 is supplied to one input terminal of the exclusive OR 28, and is exclusive ORed with the received signal 18 inputted to the other input terminal thereof. An output signal 32 is obtained. This output signal 32 is applied to the input end of flip/flop 26. A reception clock 31 from the synchronization circuit 23 is input to an input terminal T of the slip/flop 26 . The output signal 33 from the output terminal Q of the clip/flop 26 is supplied to the input terminal of the flip/70 tube 27.
A collision detection signal 19 is obtained from the output terminal Q of .

The operation of the collision detection section 13' will be explained below with reference to FIG. 9.

In FIGS. 8 and 9, the received signal 18 is
T7 lip/70 lip (hereinafter abbreviated as F/F) 24.2
5, synchronization is established with the sampling crotch 34,
The signal is shifted by 1/2 bit in a shift register to obtain a comparison signal 3o. By comparing the received signal 18 and the comparison signal 3o, it is possible to monitor that the signal level always inverts before and after the center of the bit, according to the Manchester code convention. The clock component of the received signal 18 is sent to the synchronization circuit 2.
When the rising edge of the pulse of the reception clock 31 extracted by 3 is viewed from multiple positions, the reception signal 18 and the comparison signal 30 correspond to the second half and first half of the center bit of the Manchester code, respectively. Therefore, if the received signal 18 conforms to the rules of the Manchester code, the signal levels of the received signal 18 and the comparison signal 3o will always be opposite if the pulse of the comparison signal 30 rises at multiple positions. Therefore, the output 32 of the exclusive OR circuit 28 is
The rise of the reception clock is always "1" at multiple positions (Fig. 9, period To).

However, when a collision occurs and the Manchester code rules are broken, the output signal 32 of the exclusive OR circuit 28 becomes 0'' when the reception clock 31 rises at multiple positions, as shown in period To2 in FIG. Therefore, the Q output signal 33 of the F/F 26 obtained by sampling the output 32 of the exclusive OR circuit 28 using the reception clock 31 will be
It rises from '0'' to ''1''. By latching this with the F/F 27, it is possible to obtain the collision detection signal 19.

In this way, it is possible to directly detect a collision from the received data regardless of whether the own node 1 has transmitted the data, so it is possible to detect not only a collision between the own node but also a collision between other nodes.

Next, a procedure for prioritizing retransmission in the event of a collision with another node based on the collision detection described above will be explained using FIG.

First, transmission during normal times is the same as in the conventional example, and the node 13
, lh until a collision occurs, the explanation is exactly the same as in FIG. 5. That is, node 1, which internally generated a transmission request at time taox, performs carrier sense at time taox, and if the line is free, transmits the text. Node IJ, lh is at time N t aos w t ao 4
A transmission request is made at , carrier sense is performed, and when carrier off is detected at time tans, transmission is performed. Node IJ,lk
If a collision occurs between nodes, each node waits for a wait time TJI*Th1 assigned in descending order of node number.

Here, if the node number is nl and the minimum wait time is ΔT, then the first wait time T a 1 of node 1 is T1;ΔT-n (4).

ΔT is the smallest possible value that can be determined by software. Therefore, T o + T** is as follows.

T1凰==ΔT−j、Tht=ΔT−k...
(5) While node IJ waits for TJl,
Continue doing Career Sense and measure the time during the Career Otsu section. If 4 other nodes 1 (node 1l-1, which has a lower number than node IJ) do not transmit after TJI,
At time thO*, node IJ starts transmitting. on the other hand,
Node 1 also measures the time of the carrier off section while waiting for Thx. In this case, carrier-off continues until node 11 transmits, so node 1 measures TJI as carrier-off time. Tb
! After the lapse of time, since the carrier of "Node 1" exists on the transmission path 2, Node 1 waits for the carrier to turn off. When node 11 finishes transmitting and detects carrier off at time tact, node 1 is further weighted by Ths (time t, I2 to taia). At this time, Tit is Tk2=Tht T11 (6). This means that if the numbers of node IJ and node 1 are far apart,
There is a possibility that nodes 1 with numbers between j and k will retransmit.
It is from.

Thereafter, the weighting is the same as the first weighting. If node 1 with a number between j and k does not retransmit, node 1 has T
After elapse of k2, the data is transmitted from time tai4, and the retransmission is successful.

Further, all other nodes including the node It which was not transmitting at the time of the collision recognize that the collision has occurred in another node by the above-mentioned 7.-doware. From the carrier-off immediately after the collision, the node 1t and other nodes 1 measure the time of the carrier-off section. Until this measurement time reaches the specified value To, all the nodes that have detected the collision with other nodes are: To=Δ'l'-m (7) where m is the maximum node number. In other words, it waits until the node 1° that has the longest wait time starts retransmission. Tsumashi,
In the case of node 1t, it waits until Tvt +Tv* +Ts = To - (8) before transmitting. At this point, the history of collisions with other nodes is cleared for all nodes.

According to the above procedure, the nodes 1 that require retransmission can always retransmit in the order of the node 1's subscript number from the smallest, and no collision will occur during retransmission.

Therefore, unnecessary occupation of the transmission path 2 due to repeated retransmissions can be eliminated, and overall efficiency is improved.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to detect collisions not only between the own node but also between other nodes, and because the transmission path is cleared with priority given to retransmission, retransmission can be performed reliably once. This eliminates the need for delayed retransmissions and significantly reduces the number of collisions, thereby improving the immediacy of transmission over the transmission network.

This has the effect of significantly improving reliability and efficiency.

[Brief explanation of drawings]

Figure 1 is a configuration diagram showing the overall configuration of the information communication system;
FIG. 2 is a block diagram showing the internal configuration of a node used in a conventional information communication system, FIG. 3 is a circuit diagram showing the configuration of a collision detection section provided in a conventional 7-board, and FIG. 5 is a time chart showing the transmission procedure of a conventional information communication system. FIG. 6 is an internal diagram of a node used in an embodiment of the information communication system according to the present invention. Block diagram showing the configuration, No. 7
The figure shows the transmission code used in one embodiment of the present invention: day → toss, 4 tos ζV;÷→to setting 1jR day M white to standing 1+
→hi 2 low i) - A block diagram showing the detailed configuration of the collision detection section used on the side of the driver, FIG. 9 is a time chart shown to explain the operation of FIG. 8, and FIG. 5 is a time chart shown to explain a transmission procedure of one embodiment. 1. 11 + is l is l ..., 1
．． ...Node, 2...Transmission line, 3...Terminal resistor,
4... Processor, 5... DMA control unit, 6...
- Memory, 7... Internal bus, 8... External interface, 9... Path buffer, 10... Serial/parallel conversion section, 11... Code conversion section, 12... Carrier detection section, 13.13'...Collision detection unit, 14...D-T
Flip/70 tubes, 15...exclusive OR circuit, 16
... Delay, 17... Transmission signal, 18... Reception signal, 19... Collision detection signal, 20... Comparison reference signal, 21... Exclusive OR circuit output, 22... Sampling Clock, 23...Text, 24°25.2
6.27...D-T flip/flop, 28...
Exclusive OR circuit, 29...shift register. Agent Patent Attorney Tatsuyuki Unuma No. 2 tank 3 drawing oval 6 also Yukima: l i l : (i print 8

Claims (1)

[Claims] 1. Information communication in which transmission path resources are shared between a plurality of transmitting and receiving stations, and each transmitting and receiving station is equipped with at least a carrier detection unit that detects the usage status of the transmission path and a collision detection unit that detects whether transmission is colliding. In the system, a fixed transmission code is used, and the collision detection unit in each transmitting/receiving station determines whether the transmission code on the transmission path violates the above regulations.Collision occurs when multiple transmitting/receiving signals are transmitted simultaneously. If the collision detection section detects that a collision has occurred between other transmitting and receiving stations, the retransmission of the information transmitted from the previously colliding transmitting and receiving station is completed. An information communication system characterized by refraining its own station from transmitting transmission information for which a new transmission request has been generated.