STAR CONNECTION APPARATUS THROUGH FLAT CABLE

Abstract: Star connection apparatus through flat cable for modu­ lar electronic systems wherein a central unit (MU) has to exchange electrical signals with each of a plurality of peripheral units (U1, U2, UN) having identical connection interface and wherein a flat cable (21) is provided with a plurality of connectors (220, 221, 222, 22N), one for each unit. Each connector has a plurality of housings devoted to receive a corresponding plurality of electrical connection elements, but a selective arrangement of connection ele­ ments in the corresponding housings is actually provided. Further the connection interface in the peripheral units is provided with a number of connection terminals (41, 42, 4N) at least equal to the number of such peripheral units (31, 32, 3N, 41, 42, 4N....61, 62, 6N) and electrically connected each other.

Description: Star connection apparatus through flat cable The present invention relates to a star connection apparatus through flat cable for modular electronic systems. It is known, for instance, that in data processing systems the several units, constituted by printed circuit boards on which the electronic components are mounted, are connected each other through a set of leads devoted to the transfer and to the exchange of electrical signals among them. The units, whether they are identical or different, are modular, that is they are characterized by printed circuit boards having the same physi cal sizes and the same terminals for electrical connection with the out side. In order to reduce the number of electrical connections among the seve ral units, bus connections are used. A bus connection is characterized by that a set of N leads connects a corresponding number N of terminals of M units (with M > 2) among them and therefore allows the exchange of electrical signals among all the M connected units. Generally it is not possible or suitable to use only bus connections among several units; selective connections are also necessary which al low the exchange of electrical signals between two units of a plurality M. In particular connections are artoften necessary which allow the exchange of signals between a unit and each of M-1 units of a system. These selective connections, considered on their whole, define a socalled star connection system. Several solutions are known for carrying out such selective connections among units of an electronic system. As the units are constituted by printed circuit boards, they are paral lely arranged each other in a chassis provided with a back panel. Each unit is provided with a connector having several terminals or with an edge having connection fingers which are engaged into a corresponding female connector mounted on the back panel of the chassis. Therefore the number of female connectors mounted parallely each other on the back panel of the chassis is equal to the number of units or boards which may be installed into the chassis. The female connectors are provided with pins which are connected each other according the needs by means of the known "wire wrapping" tech nique. Alternatively the required connections among the pins of the several female connectors may be obtained by emboding the back panel as printed circuit and by soldering such pins on this last one. A connection of such kind is for instance disclosed by European patent application N. 80104872.9 published on March 11, 1982, serial number 0,024,663. The mentioned embodiments of connection among modular units are relati vely expensive. They are therefore substituted, when possible, by using the so-called flat cables constituted by a plurality of contiguous parallel leads. In this case each of the connectors of the several units is engaged in to a corresponding female connector fixed on the flat cable. Such kind of embodiment has been up to now limited to bus connection ap paratuses or to connections between two only units. In fact the use of flat cables for star connections would require deli cated and expensive flat-cable handlings, such as the separation of the several leads and/or the diversification of the connection interfaces of the several system units, so that no economical advantage is achieved. Such inconvenient is overcome by the connection apparatus of the present invention which allows to carry out in unexpensive and easy way star connections among units having the same electrical interface by means of flat cables and related connectors of conventional type avai lable on the market. According to the invention, the selective star connections between several units having the same interface (afterwards identified as peripheral units) and a common unit (afterwards identified as central unit are obtained by means ofa flat cable, a plurality of connectors mounted on such cable (such connectors being provided with a plurality of hou sings each devoted to receive a corresponding electrical connection element), a selective arrangement of connection elements and the direct electrical connection of several corresponding terminals in each of the units to be star connected with the common unit. These and other features of the invention will appear clearer from the following description of a preferred embodiment and from the enclosed drawings where: Figure 1 schematically shows a mixed star and bus connection system al ready known in the art, between a central unit and several pe ripheral units; Figure 2 schematically shows the embodiment, known in the art, of a bus connection apparatus through flat cable for the system of fig. 1; Figure 3 shows in perspective exploded view an electrical connection, known in the art, among flat cable, connector and electronic unit; Figure 4 schematically shows the preferred embodiment of a star connec tion apparatus through flat cable according to the invention. Fig. 1 schematically shows a modular electronic system known in the art. The system comprises a main or central unit MU and N modular units U1, U2 .... UN. Such a structure may be for instance representative of the modular memories of data processing systems. In this case main unit MU is representative of a memory control unit and units U1 ... UN are representative of memory modules identical one another at least with reference to the interface, that is with referen ce to the electrical/logical connections with the main unit MU. Units U1, UN communicate each other and with main unit MU through a set of leads or common channel or bus shown in fig. 1 by two leads 10, 11. As shown in fig.1, lead 10 electrically connects each other a terminal 12 of unit MU and a corresponding terminal 121, 122 12N of units U1, U2, UN. Likewise lead 11 electrically connects each other a terminal 13 of unit MU and a corresponding terminal 131, 132, 13N of units U1, U2, UN. An electrical signal applied by any of the units on leads 12 and 13 is received by all the other units. Such type of connection is named "bus connection" and can be easily em bodied with a flat cable, as shown in fig 2. In fig. 2, two leads L10, L11 are representative of a flat cable. A connector 14 is fixed and electrically connected to one end of the ca ble, such connector electrically connecting the cable leads to terminals 12, 13 of unit MU. N connectors 141, 142, 14N are fixed and electrically connected along the cable, such connectors electrically connecting the cable leads re spectively to terminals 121, 131 .... 12N, 13N of units U1, UN. The flat cable connectors may be, for instance, of the type disclosed in US Patent N. 3,434,093. For a better understanding of the invention, Fig. 3 shows in exploded view a flat-cable connector and its connection, on a side, with the flat cable and, on the other one, with an electronic unit. The connector comprises an insulating body 70 provided with housings, such as 71, where electrical connection elements, such as 72, are engaged. Such elements have a fork shaped end, such as 73 for element 72, which protrudes from the insulating body. Flat cable 74 is clamped between insulating body 70 and an insulating back element 75, by means of two screws 76, 77 or other equivalent devices. In such way the fork-shaped terminals pierce insulating material 78 of the cable and each of them is electrically connected with a correspon ding lead of the cable, such as 79. Each of the insulating body housing, such as 71, where the electrical connection elements, such as 72, are engaged, receives a corresponding terminal or pin, such as 80, of a male connector 81 fixed on the con- nection edge of a printed circuit of an electronic unit 82. The pins of male connector 81 are electrically contacted with the cor responding connection elements of the flat cable connector. It is to be noted that, when the flat cable connector is disassembled, the connection elements, such as 72, may be easily withdrawn from their housings. Considering again fig. 1, a lead 15 electrically connects a terminal 16 of unit MU to a terminal 161 of unit U1. The connection enables the exchange of electrical signals only between unit MU and U1. Likewise a lead 17 (19) electrically connects a terminal 18 (20) of unit MU to a terminal 182 (20N) of unit U2 (UN). The set of such connections constitutes a star connection between units U1, .... UN, and unit MU. This star connection allows, for instance, unit MU to select a unit Ui among units U1, ... UN in order that only this one be enabled to recei ve from/to send to unit MU some signals through the bus (leads 10, 11 of fig. 1). In this way it is avoided that signals present on leads 10, 11 and in tended for unit Ui be received by other units different from the selec ted unit Ui or that units different from the selected unit Ui apply at the same time some signals on leads 10, 11. Fig. 3 shows a preferred embodiment of a star connection system through flat cable according to the invention. The system comprises a flat cable 21, N+1 flat cable connectors 220, 221, 222, 22N and N+1 units MU, U1, ... UN, each provided with a connection edge(E0, El, E2, EN respectively)having connection fingers. The flat cable comprises a plurality of leads greater than or equal to N (21; 212, 21N). Such leads are parallely arranged one another between two tapes of insulating material (not shown). The insulating body of the connectors is represented by a rectangle arranged transversally to the flat cable (in the practical embodiment it is arranged perpendicularly ). The circles shown inside each connector body represent the housing for the electrical connection elements, each one arranged next to a flat cable lead. A black mark inside a housing indicates that a connection element is present in such housing. If the black mark is missing, this means that the connection element is not present. A selective arrangement of connection elements into the corresponding connector housings can be obtained during the connector manufacturing process through a selective inserting of the connection elements, as well as during the assembling process of the connection system. In this last case the connection elements can be selectively withdrawn from the housings of a connector provided with a connection element in each housing. The connection edge of each of units MU, U1, U1, UN is provided with at least N contact fingers 31, 32, 3N, 41, 42, 4N, 51, 52, 5N, 61, 62, 6N respectively. As to their interfaces, units Ul, U2, UN are identical. The star connection between unit MU and each of units U1, U2, UN is ob tained as follows. Connector 220 is provided with connection elements in all the housings devoted to receive contact fingers 31, 32, 3N of unit MU. Connector 221 is provided with a connection element in the housing devoted to receive contact finger 41 of unit U1, but it is not provided with connection elements in the housings devoted to receive contact fin gers 42, 4N of unit U1. Connector 222 is provided with a connection element in the housing devoted to receive contact finger 52 of unit U2, but it is not provided with connection elements in the housings devoted to receive contact fingers 51 and 5N of unit U2. Connector 22N is provided with a connection element in the housing devoted to receive contact finger 6N of unit UN, but it is not provided with connection elements in the housings devoted to receive contact fingers 61, 62 of unit UN. Terminals 41, 42, 4N of unit 1 are connected together by a lead C1, car ried out for instance on the printed circuit of unit U1, and functional ly constitute a single terminal T1 of unit U1. Terminals 51, 52, 5N of unit U2 are connected together by a lead C2 and functionally constitute a single terminal T2 of unit U2. The terminals of unit UN are connected together by a lead CN and func tionally consitute a single terminal TN of unit UN. Units U1, U2, UN are therefore identical, as to their interfaces at least, and provided with a terminal T which is practically obtained through the electrical connection of N connection fingers arranged in the same way. The system shown in fig. 3 therefore allows to obtain an electrical connection between terminal 31 of unit MU and terminal T1 of unit U1 through lead 211, an electrical connection between terminal 32 of unit MU and terminal T2 of unit U2 through lead 212, and an electrical con nection between terminal 3N of unit MU and terminal TN of unit UN. In other words a star connection is obtained between unit MU and each of units U1, U2, UN without particular handlings of the flat cable and without the need of differentiating units U1, U2, UN as to their interfaces. For simplicity purposes, only a star connection apparatus has been shown in fig. 3. But, practically, the described apparatus can be used for carrying out mixed connections, that is bus and star connections. Therefore it completely fulfils the requirements not only of the modular memory systems used in data processing systems, but also the ones of the multiprocessor systems where several processors communicate with a memory through a bus connection and a star connection is provided for between an access memory control unit and each of the processors, as for instance disclosed in US Patent N. 4,302,808. It must be therefore clear that the expressions "common or central unit" and "peripheral unit" do not set limits to the application fields of the invention, but they are used for clearness purposes in order to distinguish the electrical device which is functionally at the centre of the star connection from the other devices. Likewise, even if an embodiment having only one star connection has been disclosed, it is obvious to carry out multiple star connections, that is star connection with several leads between central unit and several peripheral units or among several central units and several peripheral units. Further, when problems of electrical load,(that is of current flowing into the leads) have to be solved, it is possible to carry out a star connection with sharing of electrical load among several leads and se veral connection elements through a multiplexing of them.

Claims: Claims. 1. Star connection apparatus through flat cable among an electronic central unit and several peripheral units, said units having a plu rality of connection terminals characterized by that it comprises: - a flat cable with a plurality of parallel electrical leads, - a plurality of connectors (220, 221, 222, 22N) mounted on said ca ble, each one for engagement with a corresponding unit, each of said connectors being provided with a plurality of housings is 71) devoted to receive a corresponding plurality of electrical connection elements (as 72),-each of said elements, when present, electrically connecting one of said leads with a terminal of the corresponding unit engaged in the connector, - and a set of connection elements selectively arranged in said plurality of housings of each of the connectors corresponding to said peripheral units. 2. Star connection apparatus as per claim 1 characterized by that it comprises, in each of said peripheral units an electrical connection among some terminals of said plurality, the terminals of each peri pheral unit electrically connected each other being connected to said leads of said flat cable through said selectively arranged con nection elements so as to provide a mutually exclusive connection of each one of said peripheral units to one of said leads.

Inventors: MANTELLINA, CALOGERO
Applicants: HONEYWELL INFORMATION SYSTEMS ITALIA S.P.A.
Application year: 1983
Main classification: H01R29
IPC codes: H05K7, H01R29