FR2635934A1 - Seqenced one-way link for intercommunication of data processing modules, especially of computers - Google Patents

Abstract

The aim of the invention is to provide a network in which each subscriber can dynamically manage access to the intercommunication link. This makes it possible to do away with centralised arbitration, and to provide a theoretical maximum throughput proportional to the number of subscribers. This aim is achieved with the aid of a one-way link 21 consisting of means of conveying in parallel, for each word transmitted by the network, on the one hand the corresponding datum, and on the other hand an identifier for the said datum, and of an exchanger module associated with each data processing module 22, 23, 24, which affords the connection to the network of the associated module, each exchanger module including: . means for interpreting the said identifier associated with each datum; . means for selective acquisition of the data intended for the processing module; . means for write-retransmission over the network of the current word received by the exchanger module; . means for writing to the network a new word originating from the associated processing module; . means for clearing the said word received by the exchanger module.

Description

One-way sequenced link
intercommunication of processing modules
data, including computers.

 The field of the invention is that of networks for putting data processing modules into communication, allowing each module to send data to another module connected to the network, and to receive data sent to it from the network.

 In this type of network, words circulate on a link accessible to all subscribers. The words are circulated by moving each word from "box" to "box", along the link, at each clock period.

 Such a network finds, for example, a non-limiting application for the intercommunication of computers.

 The computers are in particular used to carry out signal processing, that is to say to carry out on a signal a certain number of successive operations on data which arrive in significant number. When a computer even of high power is not enough, it is necessary to implement the processing by several computers which must therefore intercommunicate.

We already know computer intercommunication networks, constituted by devices as shown in FIG. 1A and 1B,
The known network of FIG. 1A consists of a linear data bus 10 to which subscriber computers 11, 12, 13 are connected. These computers communicate with the bus 10 through input-output buffer circuits 14, 15, 16, respectively.

 The type of computer known in FIG. 1B comprises a circulating and closed bus 17, to which computers 18, 19, 20 are connected through buffer circuits 21, 22, 23.

 These buses 10, 17 generally use centralized access arbitration, which particularizes one or more of the subscribers. On the other hand, the total bandwidth, and therefore the total speed is shared between the different subscribers, which limits the number of connectable subscribers.

Networks are also known which allow decentralization of access arbitration. We can thus cite in the case of linear buses, the
Gibus, or the Ethernet bus. In these networks, each subscriber detects for himself whether the bus is free, and resolves collision problems.

In the area of rotating buses, we can point out that of the CAPITAN calculator, where each active subscriber is associated with a time slot for bus access: "The CAPITAN 600 MIPS parallel calculator for real-time imaging" (Gérard
Gaillat, first Image Colloquium, Biarritz, May 1984). More prec: #ent in this parallel computer, the intercommunication link of the different processing modules is divided into successive circulating "boxes", forming trains of "boxes" of which at least certain boxes of determined rank in the train are specifically affected the transmission of information intended for one or more specific subscribers. An improvement to this type of bus can also be found in French patent publication 2571567.

 These existing decentralized networks have the disadvantage of sharing the bandwidth between the subscribers.

 The subject of the invention is a network which makes it possible in particular to overcome the various drawbacks of existing networks.

 More specifically, a first objective of the invention is to provide a network in which each subscriber is capable of dynamically managing access to the inter-communication link. This allows to get rid of centralized arbitration, and to provide a theoretical maximum speed proportional to the number of subscribers.

 A complementary objective is to provide such a network which is compatible with a unidirectional link either linear or rotating (that is to say in a ring).

 Another objective of the invention is to provide such a network allowing both the distribution of each data item to a specific subscriber of the network, as well as the dissemination of one item of data to several subscribers.

These objectives, as well as others which will appear subsequently, are achieved using an intercom network of data processing modules, in particular of computers, of the type constituted by a one-way data transmission link, linear or ring, said data being transmitted in time multiplex in the form of successive words originating from and / or being intended for at least one of said modules connected to the network,
characterized in that said unidirectional link is made up of parallel routing means, for each word transmitted by the network, on the one hand of the corresponding data, and on the other hand of an identifier of said data,
and in that an exchanger module, associated with each data processing module, ensures the connection to the network of the associated module, each exchanger module comprising
means of interpretation of said identifier associated with each data item
means for the selective acquisition of data intended for the processing module
re-transmission means for writing to the network of the current word received by the exchanger module
means for writing a new word on the network from the associated processing module
means for emptying said word received by the exchanger module,
each of said means of acquisition, writing, retransmission and emptying being selectively controlled by said means of interpretation of said identifier.

Advantageously, said exchanger means each comprise common means for writing to the network the current word received and / or a new word, constituted by a set of two synchronized multiplexers, a first of said multiplexers ensuring the routing of the data of each word, and the second multiplexer ensuring the referral of the identifier of the current word,
said multiplexers being able to take three positions, under control of said identifier interpretation means
a first retransmission position on the network of the current word received
a second position for writing a new word on the network
a third position of abstention from writing on the network for the current cycle.

According to another characteristic of the invention, said exchanger module comprises three consecutive word storage registers, the first and third of said registers ensuring the interface of the exchanger module with the network, at the input and output of said exchanger module respectively, said identifier interpretation means are connected between the first and second of said registers, and the selective word reading and writing means are mounted between the second and third of said registers, said exchanger module operating according to a cycle of three clock periods
a first power cycle of said identifier interpretation means with the value of the identifier of the current word received
a second control cycle of the reading and writing means by said identifier interpretation means
a third word writing cycle on the network at the output of the exchanger module.

 In order to allow the dissemination of data to several subscribers of the network of the invention, said identifier advantageously consists of a first subfield containing information addressing the current data and a second subfield containing a diffusion information of the current word to several data processing modules.

Other characteristics and advantages of the invention will appear on reading the following description of a preferred embodiment of the invention, given by way of illustration and not limitation, and the appended drawings in which
FIGS. 1A, 1B show diagrammatically the morphology of known networks of the linear type (FIG. 1A) and in a ring (FIG. 1B)
FIG. 2 diagrams the morphology of the intercommunication network according to the invention
FIG. 3 represents the different functional elements characteristic of the exchanger module associated with each data processing module connected to the network according to the invention; ;
FIGS. 4A, AB, 4C show diagrammatically the routing, the distribution and the writing of data on the network of the invention, for three consecutive subscribers, during three successive clock periods
FIG. 5 represents the block diagram of a preferred embodiment of an exchanger module according to the invention, intended to operate with a one-way link carrying 30-bit words.

 The morphology of the unidirectional link network of the invention is shown in FIG. 2.

 The link 21, linear or ring, allows the intercommunication of several subscribers 22, 23, 24.

 Access to the network of each subscriber 22, 23, 24 is effected, in a decentralized manner, through exchanger modules 25, 26, 27 inserted in the one-way link 21.

 Each exchanger module 25, 26, 27 communicates with its subscriber 22, 23, 24 respectively through an input / output buffer 28, 29, 30.

 FIG. 3 represents the diagram of a changer module according to the invention, associated with a specific subscriber. There are as many exchangers as subscribers and they are all essentially identical.

 Each word transmitted by the link 21 is mainly broken down into two fields (each field is a number of pairs of signals carrying 1 bit): a "data" field 31 and an "identifier" field 32. If the data 31 are, for definition, processed in the subscribers, on the other hand, the identifier 32 does not appear in the subscribers, it only travels on the bus to control the exchanger.

The functions of the exchanger
to receive the words transmitted by the link 21,
. to interpret the identifier 32 and to act accordingly, that is to say to acquire the data of which it is the recipient, to let transit the others and to send data as soon as possible out of the subscriber.

 The data 31 and the identifier 32 are conveyed on the bus at the rate of a clock of period T.

 The exchanger module operates in 3 clock strokes (3T), plus one stroke for clock resynchronization as we will see later.

It includes, in its block diagram, three buffer registers R1, R2, R3 interfacing with the link 21. Each buffer is formed by two parts: one T1 receives the "given" field, the other
T2 receives the "identifier" field.

 To interface with the subscriber, the exchanger includes an inlet buffer 38 and an outlet buffer 39.

 The "core" of the exchanger consists of two multiplexers 33, 34 with three positions, one on the given link 31, the other on the identifier link 32. These multiplexers 33, 34 implement actions 40 to perform on data and identifiers.

 A switch 37 controlled on the connection between the link 21 and the input buffer 38 participates in the development of the actions, by constituting a selective switching means ensuring the acquisition of the words received by the exchanger module and intended for the processing module. associated with the exchanger module.

 A register 41 temporarily stores the identifiers of the words newly written on the network, coming from the subscriber.

 Actions 40 are caused by a control module 44 acting on the multiplexers 33, 34, and the switch 37.

 These actions are programmed by the subscriber (pairs address 42 / action 43) according to the identifiers to which he is aware. This programming takes place in random access memory (RAM) 35 with also writing to the register 41, by the management unit (U.G.) 36 of the subscriber and is therefore easily modifiable by the subscriber.

The two data multiplexers 33 and identifier 34 work in synchronism so that there are six possible actions indicated in the table below, corresponding to the 6 combinations of the positions of the multiplexers 33, 34 and of the switch 37
ACTION TABLE
Switch 37 Multiplexers Action
Input buffer 33 34 40
1 open position 1 Pass
2 closed position 1 Read data
and let
pass
3 closed position 3 Read and "emptying"
of the identifier
and data
4 closed position 2 Read and write
5 open position 2 Write
6 open position 3 "Emptying" of
the identifier and
of the data
The action of reading means passing data from the link 21 to the input buffer 38 (the subscriber acquires the data).

 The act of writing means passing data from the output buffer 39 to the link 21 (the subscriber supplies the data to the network).

 The six possible actions depend on the input identifier. An identifier number is reserved for the empty identifier which signifies the absence of a word for the current period, at the input of the exchanger module.

 In the case where the identifier is empty, the action 40 carried out is either action 1 of the table of actions, when nothing is to be emitted on the network, or action 5 of the table, if a datum must be issued by the subscriber module.

In the case where the identifier is not empty, the actions 40 are as follows
non-recipient of the current word action 1
subscriber recipient of the current word action 2, if there are other recipients (distribution).

 the subscriber is the only recipient of the current word, and has nothing to put on the action 3 network.

 . the subscriber is the sole recipient of the current word and must send data on the action 4 network.

 . action 6 is reserved for the initialization of link 21.

 In FIGS. 4A, 4B, 4C, a portion of the network has been shown diagrammatically for three consecutive subscribers nl, n, n + 1 with samples of input E and output S for three successive clock periods T, T + 1 , T + 2.

For each subscriber, the changer module 45, 46, 47 is shown diagrammatically by 5 cross-shaped boxes
3 3 consecutive boxes, inserted in the link, and corresponding to the three registers R1,
R2, R3 of the exchanger module;
2 2 boxes 38, 39 corresponding to the input and output buffers respectively of the subscriber.

 The inscriptions Eij and S in the boxes correspond to the word coming from, or intended for the link 21. The index i identifies the subscriber intended for the data contained in the word, and the exponent j orders, for information, words from the same destination.

 From T to T + 1, the action relating to the exchanger n-l is "let pass", that relating to the exchangers n and n + l is "read and write". From T + 1 to T + 2, the action relating to the exchanger n-l is "read and write" while that relating to the exchangers n and n + l is n pass ".

 This explanatory example of the principle further indicates that in order to be able to write, the output register R3 must be freed, either by the subscriber itself because the sample in the register R2 is read (this is the case of the figures), or because the register is empty.

 The multiplexers 33, 34 and the switch 37 are controlled from an analysis of the identifier of each word between the input register R1 and the register R2. For this, at time T, the identifier addresses the RAM memory 35 which contains the list of actions as a function of all the identifiers. RAM 35 provides the command word which defines the actions.

 At time T + 1, the commands shown in broken lines in FIG. 3 are carried out.

In summary
if the subscriber is the recipient of the data, he takes it, can modify the identifier and possibly sends a data in # output,
otherwise it lets pass the data and the identifier,
or if the data is empty, it optionally emits data as an output with a new identifier.

 The empty identifier (position 3) corresponds to a given empty field 31.

 In the case where a subscriber has to broadcast data to several subscribers, the identifier contains this information in the form of the number of recipients minus one (distribution code).

The exchanger that recognizes the input identifier acquires the data and tests the broadcast code. If its value is not zero, it decrements it and sends the data and the new identifier to the next subscriber. If its value is zero, it is the only one or the last concerned by the data and puts the identifier empty.

 FIG. 5 represents a preferred embodiment of a changer module according to the invention, intended to operate with a one-way link carrying 30-bit words.

 These words are, for example, transmitted by a standard cable, of the "marine" type, consisting of 30 twisted pairs.

 In these 30-bit words, the "data" field has 16 bits plus 1 parity bit, the "identifier" field has 12 bits, 2 of which correspond to the broadcast field and 1 to parity. A wire is reserved for the transmission of the clock signal of period T.

 The functional elements of Figure 5, which correspond to those of Figure 3, have the same references.

The size of the main internal connections to the exchanger module of Figure 5 are expressed in binary elements (eb),
Unlike the exchanger module of Figure 3, the exchanger module of Figure S includes an additional register 51 located upstream of the input register R1 to perform resynchronization 52 of the internal clock 53 of each subscriber on the master clock.

 For a linear link, the master clock is the internal clock of the most upstream subscriber called the initial subscriber. For a ring-type link, the initial subscriber can be any one and is designated during initialization by the supervisor. It is considered to be the closing point of the ring and it ensures resynchronization between its incoming and outgoing flows so as not to lose data in transit.

 The programming of the RAM memory 35 for sending control words 40 from the identifier of each word transmitted by the network is carried out under the control of a sequencer 54 controlled by the management unit 36 of the processing module associated with the exchanger module.

 The management unit 36 of the processing module dirtyly commands a module 41 for transmitting, on 12 eb, the identifier of each new data item written on the link 21, at the output of the exchanger module.

 As in FIG. 3, this data comes from a FIFO buffer circuit 39 connected to the internal bus 56 of the processing module.

Claims (7)

 1. Intercommunication network of data processing modules, in particular of computers, of the type constituted by a one-way data transmission link, linear or ring, said data being routed in time multiplex in the form of successive words originating from and / or being intended for at least one of said modules connected to the network,  characterized in that said one-way link (21) consists of parallel routing means, for each word transmitted by the network, on the one hand of the corresponding data (31), and on the other hand of an identifier ( 32) of said data (31),  and in that an exchanger module (25, 26, 27), associated with each data processing module (22, 23, 24), ensures the connection to the network of the associated module, each exchanger module comprising  means (35, 44) for interpreting said identifier associated with each data item  means (37) for the selective acquisition of data intended for the processing module  means (33, 34) for writing re-transmission on the network of the current word received by the exchanger module  means (33,34) for writing on the network a new word coming from the associated processing module  means (33, 34) for emptying said word received by the exchanger module,  each of said acquisition, writing, re-transmission and emptying means being selectively controlled by said means (35) for interpreting said identifier.  2. Network according to claim 1 characterized in that each of said exchanger modules comprises common means for writing on the network the current word received and / or a new word, constituted by a set of two multiplexers (33,34) synchronized, a first (33) of said multiplexers ensuring the routing of the data (31) of each word, and the second (34) multiplexer ensuring the routing of the identifier (32) of said current word,  said multiplexers (33,34) being capable of taking three positions (1,2,3), under control of said identifier interpretation means (35,44)  a first position (1) for re-transmission on the network of the current word received  a second position (2) for writing a new word on the network  a third position (3) to abstain from writing to the network for the current cycle.  3. Network according to claim 1, characterized in that said exchanger modules comprise means for acquiring the current word received constituted by means (37) for selective switching to an input buffer (38) of the processing module of data associated with said exchanger module, said switching means (37) being controlled by said means for interpreting the identifier (35,44).  4. Network according to claim 1, characterized in that said identifier interpretation means (35,44) are constituted by a circuit (35) for decoding the identifier part of the current word received, and for generating a corresponding control word (40).  5. Network according to claim 4, characterized in that said decoding circuit (35) consists of a random access memory, programmable by the data processing module associated with the exchanger module.  6. Network according to claim 1 characterized in that said exchanger module comprises three consecutive word storage registers (R1, R2, R3), the first (R1) and the third (R3) of said registers ensuring the interface of the exchanger module with the network (21), at the input and output of said exchanger module respectively,  and in that said identifier interpretation means (35,44) are connected between the first (R1) and the second (R2) of said registers and the means for selective reading and writing of words are mounted between the second (R2) and the third (R3) of said registers, said exchanger module operating according to a cycle of three clock periods::  a first supply cycle of said identifier interpretation means (35,44) with the value of the identifier (32) of the current word received  a second cycle of control of the means (33, 34, 35) of reading and writing by said means of interpretation of identifier (35,44)  a third word writing cycle on the network (21) at the output of the exchanger module.  7. Network according to claim 1, characterized in that said identifier (32) consists of a first sub-field containing information addressing the current data and a second sub-field containing information broadcasting the common word in several data processing modules.