GB2168214A - Data handling systems - Google Patents

Abstract

A data handling system comprising a multiplicity of data processing modules 1, 3 releasably retained side by side in a rack 5 and interconnected by optical links 7, 9. The transmission medium of each link suitably includes an air gap 13 so that each module can easily be withdrawn from the rack, when desired. The modules are preferably so interconnected as to form a data transmission ring. In a second embodiment (Fig. 3 not shown) a fibre optic element (17) is included in the air gap. <IMAGE>

Description

SPECIFICATION Data handling systems This invention relates to data handling systems.

More particularly the invention relates to data handling systems of the kind (hereafter referred to as the kind specified) comprising: a multiplicity of data processing modules which are releasably retained in a rack; and means interconnecting the modules for the transmission of data therebetween.

In conventional forms of such a system each module comprises a circuit board carrying electric components and connections between the components, and at least one connector part, e.g. an edge connector, connected with said components and adapted to mate with a respective one of a multiplicity of complementary connector parts carried on a mother circuit board, or backplane. The backplane carries a complex of connections which provide the desired interconnections between the modules, and also carries further connections and one or more further connectors by means of which the modules may receive power inputs and receive inputs from and deliver outputs to associated equipments, for example, in the case of an avionics system, gyros, air data systems and electric or electrohydraulic actuators.

In such a system of any complexity, the connector between each module and the backplane necessarily has a large number of pin and socket connections, with the consequent reliability problems associated with such connections.

It is an object of the present invention to provide a data handling system of the kind specified wherein this problem is alleviated.

According to the present invention in a data handling system of the kind specified interconnection between the modules is provided at least partly by way of optical data links between the modules.

Preferably said optical data links form part of a data transmission ring linking the modules.

In one such arrangement the modules are disposed along the rack in side by side relationship; and each said optical data transmitter and an optical data receiver respectively associated with adjacent modules.

In one particular such arrangement a single said optical link is provided between each adjacent pair of modules in the rack and the end modules in the rack are connected by an electrical data link to complete said ring.

In another particular such arrangement two said optical links having opposite propagation directions are provided between each adjacent pair of modules in the rack and each end module in the rack provides an electrical data link to complete said ring.

In a system according to the invention the transmission path of each said optical link preferably includes an air gap to facilitate removal of modules from the rack.

Two data handling systems in accordance with the invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a schematic diagram illustrating the first arrangement; Figure 2 is a diagram illustrating the mode of operation of the arrangement of Fig. 1; Figure 3 illustrates a modification of the arrangement of Fig. 1; and Figure 4 illustrates a module for use in the second arrangement.

Referring to Fig. 1, the first arrangement to be described comprises a number of data processing modules 1, 3 disposed side by side along the length of a rack 5.

One end module 3 carries an optical data receiver 7 and the other end module 3 carries a optical data transmitter 9.

Each intermediate module 1 along the length of the rack 5 carries an optical data receiver 7 on one side and an optical data transmitter 9 on its opposite side.

Each receiver 7 converts received optical signals to electrical signals and supplies them to a terminal 11 connected with the electric circuitry of the associated module 1 or 3.

Each transmitter 9 receives electrical signals from the associated terminal 11 and transmits them as optical signals.

Each receiver 7 receives optical data from the transmitter 9 on the adjacent module 1 or 3 to one side and each transmitter 9 transmits optical data to the receiver 7 on the adjacent module 1 or 3 to the other side. The transmission path between each transmitter 9 and receiver 7 is constituted by an air gap 13 to facilitate withdrawal of the modules from the rack.

The end modules 3 in the rack are connected by an electrical data link 15.

The arrangement constitutes a so-called active data transmission ring of the kind well known in the computer art. Thus, as illustrated in Fig. 2, the modules 1, 3 are disposed at spaced positions around a unidirectional data transmission ring 13, 15. In operation, a module requiring to transmit data takes control of the ring and transmits a message to its neighbour in the transmitting direction. The neighbour will receive the message and instantaneously re-transmit it to its neighbour in the transmitting direction. At the same time the module will inspect the contents of the message to see if it is addressed to itself.

If a module receives a message for itself, it will direct the message to its own circuitry as well as re-transmitting it to the next module on the ring. If the message is not intended for itself, it will simply re-transmit the message to the next module. This action is repeated until the module that sent the original message receives it back again. At this point the originating module removes the message from the ring; the module can then send another message or relay control to another module so it can send a message.

Referring now to Fig. 3, in a modification of the arrangement of Fig. 1, each transmission path between a receiver 7 and a transmitter 9, instead of being constituted wholly by an air gap, is constituted by a light guide 17, e.g.

a fibre optic element, with an air gap 19 at each end.

In the second arrangement to be described, two optical links having opposite propagation directions are provided between each adjacent pair of modules 1, 3. The active data ring then comprises the series connection of optical links of one direction of propagation, an electrical data link between the receiver and transmitter of one end module, the series connection of the optical links of the other direction of propagation, and an electrical data link between the receiver and transmitter of the other end module.

An intermediate module for use in such an arrangement is illustrated in Fig. 4. The module has a first receiver 7a and a first transmitter 9a on opposite sides of the module adjacent one edge 21 of the module, and a second receiver 7b and a second transmitter 9b on opposite sides of the module adjacent the opposite edge 23 of the module, the first receiver 7a and second transmitter 9b being on one side of the module, and the first transmitter 9a and the second receiver 7b being on the other side of the module. The transmitter and receivers and associated terminals (not shown) are suitably carried by an electric connector part 25 which mates with an edge connector of a printed circuit board 27 carrying the circuitry of the module. The end modules (not shown) are similar but with a receiver and transmitter on one side only interconnected via an electrical data link.

It will be appreciated that in a system according to the invention a backplane or equivalent means (not shown) will also normally be provided to connect the modules with power supplies and other associated equipment, which backplane may conveniently be connected with the modules using conventional pin and socket electrical connectors.

However, the backplane will be of substantially less complexity than those employed in comparable known systems in which all of the data between modules is routed by way of the backplane. Furthermore, the connections between the modules and the backplane are considerably less numerous than is required in such known systems. The reliability of the system is, for this reason at least, improved.

Claims (8)

1. A data handling system comprising a multiplicity of data processing modules which are releasably retained in a rack wherein interconnection between the modules is provided by way of optical data links between the modules.

2. A system according to Claim 1 wherein said optical data links form part of a data transmission ring linking the modules.

3. A system according to Claim 2 wherein the modules are disposed along the rack in side by side relationship; and each said optical data link comprises an optical data transmitter and an optical data receiver respectively associated with adjacent modules.

4. A system according to Claim 3 wherein a single said optical link is provided between each adjacent pair of modules in the rack and the end modules in the rack are connected by an electrical data link to complete said ring.

5. A system according to Claim 4 wherein two said optical links having opposite propagation directions are provided between each adjacent pair of modules in the rack and each end module in the rack provides an electrical data link to complete said ring.

6. A system according to any preceding claim wherein the transmission path of each said optical link includes an air gap to facilitate removal of modules from the rack.

7. A system according to Claim 6 wherein said transmission path includes a light guide with an air gap at each end.

8. A data handling system substantially as hereinbefore described with reference to Figs.

1 and 2, or Fig. 3, or Fig. 4 of the accompanying drawings.