FR2639135A1 - System for communication between several microcomputers - Google Patents

Abstract

The system for communication between several microcomputers 32.1, 32.2, ... 32.N each including a parallel port dedicated to the connection of printing facilities, comprises a communication bus 30 including a set of bidirectional lines for communication in parallel mode and bus control lines, and, for each microcomputer, interface means 31.1, 31.2, ..., 31.N linked, on the one hand, to the said parallel port, and, on the other hand, to the said communication bus 30. The interface means are external to the microcomputers. Use in networks of microcomputers.

Description

 The present invention relates to a communication system between several microcomputers.

 The invention also relates to the method implemented in the system.

 The connection of several microcomputers in the local network currently requires equipping them with communication cards. Only microcomputers with internal connectors can also receive these communication cards and thus be integrated into a local network.

 Figure la is a simplified block view of a communication system representative of the prior art, in which each microcomputer 2.1, 2.2, ...

2.N has an internal communication card 4.1, 4.2, ..., 4.N connected to a serial transmission line 1.

 The advantages of this system are to use an internal connector of each microcomputer to the detriment of other expansion cards or specific applications, to use complex and therefore storytelling communication cards, and to present typical transfer speeds. relatively slow data, for example of the order of 115,000 bits per second.

 There are also known systems for transferring aons and files between two microcomputers 10, it, using specific communication cards 12, 13 and a parallel transmission line 14 (FIG. 1b); the communication cards are placed in internal connectors of each microcomputer. However, no extension of these systems to more than two microcomputers is planned.

 There are also communication systems between several microcomputers 21.1, 21.2, ..., 21.N, comprising a server microcomputer 20, equipped with a specific internal communication card 22, connected in a star by parallel links 23.1, 23.2, ... 23.N, to other microcomputers also equipped with internal adaptation cards 24.1, 24.2, ..., 24.N, as illustrated in figure lc. A disadvantage of such systems is that they are bad adapted to the progressive equipment in network of professional premises. Thus, any extension of the network by adding an additional microcomputer requires either to provide a new line connecting this microcomputer to the server microcomputer, or to equip one of the microcomputers of the network to make a second server.

These solutions require modifications which generally entail installation times and additional costs.

 The object of the invention is to remedy these drawbacks by proposing an ink communication system comprising several computers comprising a parallel port dedicated to the connection of printing means.

 According to the invention, this communication system comprises a communication bus comprising a set of bidirectional lines for communication in parallel mode and control lines and, for each micro-computer, interface means connected, on the one hand, to said port parallel, and on the other hand, to said communication bus, and said interface means are located outside of said microcomputers.

 thus, with the system according to the invention, it is possible to integrate into a local network any microcomputer provided with a parallel port, most often, the connection port of the printer, even if this microcomputer does not include internal connector available. In addition, the use of parallel transmission makes it possible to considerably increase the speed of transmission of data and files between microcomputers of the network, and leaves the serial port of the microcomputers available for other applications.

 According to a preferred form of the invention, the interface means comprise means for selectively connecting the printing means to the parallel port.

 Thus, the parallel port is used for both communication and data transmission to a printer. ne system according to the invention is therefore completely "transparent" vis-à-vis any printers connected to microcomputers on the network.

Other features and advantages of the invention will appear in the description below
- Figure la is a block diagram of a first communication system between microcomputers representative of the prior art
- Figure lb is a block diagram of a data transfer system between two microcomputers representative of the prior art
- Figure lc is a block diagram of a second communication system between microcomputers representative of the prior art
- Figure 2 is a block view of the communication system according to 1 invention
- Figure 3 is a schematic view of the interface socket-outlet circuit implemented in the system according to the invention
- Figure 4 is an exterior view of an interface socket outlet according to the invention.

 An effective embodiment of a local network constituted around a communication system in accordance with the invention comprises a communication bus comprising four communication lines on which transit in parallel mode four-bit words representing either commands or data. It is possible to connect a maximum of sixteen microcomputers 32.1, 32.2, ..., 32.N to the communication bus 30 via connection cables 35.1, 35.2, 35.N and interface socket-outlets 33.1, 33.2,. .. 33.N respectively connected to the parallel ports of each microcomputer of the network, with reference to FIG. 2. Printers 34 can of course be connected to the parallel ports via the interface socket-outlets. Furthermore, a source of DC power supply 36 is connected to one of the network socket-outlets to supply all of the other socket-outlets via the communication bus 30. With this system, file transfer speeds of the order of 500,000 bits per second can be achieved.

 Software means are associated with the hardware structure according to the invention. Each microcomputer of the local network thus created is provided with communication software making it possible to manage the bidirectional accesses to the communication bus of the local network and the exchanges of data between microcomputers. This software allows you to perform multi-task treatments. A memory area of at least 384 k bytes is also required in each microcomputer.

 The interface circuit 100 according to the invention comprises a port connector 50, intended to be connected to the parallel port of the microcomputer which is associated with this circuit a printer connector 100, and a communication port 300 connected to a cable. link 30, with reference to FIG. 3.

 The parallel ports fitted to most microcomputers are essentially unidirectional with regard to data transfer since their essential application is the connection of a printer.

Thus, only the lines of control signals emitted by the printer are input lines for the parallel ports. By way of example, the lines 500 of the parallel port 50 in FIG. 3 are grouped into four groups: a first group 66 relates to output lines, a second group 54 relates to control input lines, such as the lines recognition, occupation, end of page and selection corresponding to the signals that a printer normally generates and here continues the internal input bus; a third group 53 relates to data output lines in particular, the four most significant bits of a byte, while the fourth group 61 relates to the least significant four bits and constitutes the internal output bus. The communication port 300 comprises a first group 56 of bidirectional communication lines 560, a second group 57 of bidirectional bus control lines and a third group 58 of supply lines.

 The interface circuit 100 comprises a regulation unit 73, the input of which is connected both to the power supply lines 58 and to an external connection socket 47 and the output of which delivers to all of the components of the circuit. interface regulated voltage + V. If the interface circuit 100 is effectively connected via the socket 47 to an external DC voltage source, it then supplies all of the network interface circuits with this DC voltage via the lines 58 of the communication bottom. Otherwise, the regulator receives from these same lines an unregulated direct voltage from another interface circuit. A light-emitting diode 69 connected to the regulator 73 signals the supply of the interface circuit 100.

 This comprises an output control unit 60 which controls the derivation of data transmitted by the microcomputer via the output lines 61 from the parallel port 50 to the communication bus. The output control unit comprises an identification unit 65 of transfer orders, connected to predetermined lines of the groups of output lines 66, 53, assigned as control lines, and to the group of lines 61 constituting the bus. internal output. The output of the identification unit 65 is connected to the input of a line amplification unit 80. This amplification unit transmits the output signals on the communication bus 30. It is in further connected to a display circuit 70 comprising a light-emitting diode and signaling a transfer of data to the communication bus. The identification unit furthermore performs the function of arbitrating bus conflicts and controls a display circuit 71 comprising a light-emitting diode 71 signaling a transfer to the printer. The interface circuit 100 also includes an input control unit 59 whose main function is to transfer data and commands from other microcomputers of the network via the communication bus, on the internal input input bus. of the microcomputer provided with this interface circuit. As the input lines concerned 54 are normally attacked by a printer connected to the connection port 10, a selective link unit 52 of the internal input bus 54 and of control lines 66 with the printer port 100 is provided. It is controlled by the identification unit 65.

 The input control unit 59 comprises a logic circuit this shaping 82 which processes the information coming from the communication lines 56, which are then applied to the input of a memory unit 64, of FIFO type, namely a battery. where the data entered first came out first. The input information is also applied to the inputs of a digital comparator 66 to be compared with predetermined address information present on the internal output bus 61 and specific to the site concerned.

 The input control unit 59 also comprises a multiplexer circuit 67, the inputs of which are connected both to the outputs of the memory unit 64 and to the outputs of a register 81 allowing the possible direct transfer of information present at the input of the input control unit 59, and the outputs of which are connected to the internal input bus 54.

 A communication management unit 63 is also provided for processing signals transmitted on control lines 57 of the communication bus 300, for example clock and line seizure signals, and for controlling the memory unit 64 and multiplexer 67.

 The communication management unit 63 also receives a control signal from the address comparator 66 to indicate that the site concerned has been selected.

 The interface circuit which has just been described is located in a socket-housing 40, parallelepipedal and of reduced bulk, comprising on one of its faces a male connector 42, adapted to the standard of the parallel port of the microcomputer, and on the opposite face, a connector 41 for receiving a printer cable with reference to FIG. 4. Another face of the housing has a continuous power outlet 47 while the opposite face receives a cable comprising the communication bus 43 according to inv # tion. Three light-emitting diodes 44, 45, 46 of different colors are provided on another face of the box and respectively signal the power supply of the box, the communication with a printer and a data transfer.

 Of course, the invention is not limited to the examples described and shown and numerous modifications can be made to these examples without departing from the scope of the invention.

 It is thus possible to connect a communication system according to the invention to a workstation or a server of another network. It is also possible to carry out, with a system according to the invention, rapid transfers between two hard disks without any diskette manipulation being necessary.

Claims (12)

 1. Communication system between several microcomputers (32.1, 32.2 ..., 32.N) each comprising a parallel port dedicated to the connection of printing means, characterized in that it comprises a communication bus (30) comprising a set of bidirectional lines of communication in parallel mode and bus control lines, and for each microcomputer, interface means (31.1, 32.2, ..., 31.N) connected, on the one hand, to said port parallel, and on the other hand, to said communication bus, and in that said interface means are located outside of said microcomputers.  2. System according to claim 1, characterized in that said interface means comprise means for selectively connecting said printing means to said parallel port.  3. System according to claim 2, characterized in that said interface means (100) further comprises output control means (60) for selectively connecting predetermined output lines (61) of said parallel port (50) to bidirectional lines (62) of said communication bus (30) and input control means (59) for selectively connecting predetermined input lines (54) of said parallel port (50) to said bidirectional lines (62).  4. System according to claim 3, characterized in that said interface means (100) further comprises line socket management means (63), connected to said bus control lines (57), for managing the sequencing and the bidirectional transfer of data and commands within said interface means (100).  5. System according to claim 4, characterized in that said input control means (50) comprise means (64) for memorizing data and commands from said communication lines (56), connected to said communication lines , said storage means constituting a “first in-first out” type storage stack and being controlled by said line seizure management means (63).  6. System according to claims 3 to 5, characterized in that said output control means (60) include means (65) for identifying bidirectional transfer orders of data and commands from signals from said microcomputer and transmitted on predetermined control lines (66, 53) of said parallel port (50) and to arbitrate conflicts related to said transfer.  7. System according to claim 6, characterized in that said interface means (100) further comprises means (66) for comparing addresses present on said communication lines with a predetermined site address transmitted by said microcomputer via said output lines of said parallel port.  8. System according to claims 3 to 7, characterized in that said input control means (59) further comprises multiplexing means (7), the output inputs of which are connected, on the one hand, to the outputs of said means of storage (64), and on the other hand, to said communication lines (56) via register means (66) controlled by said identification means (65), and the outputs of which are connected to said predetermined input lines ( 54) of said parallel port.  9. System according to claims 1 to 8. characterized in that said interface means (100) further comprises first (70) and second (71) display means for respectively indicating a transfer of data between said parallel port (50) and said communication bus (30) and transferring data from said parallel port (50) to said printing means.  10. System according to claims 1 to 9, characterized in that said communication bus (30) further comprises a pair (58) of direct supply lines delivering an unregulated voltage and in that said interface means ( 100) further comprise regulating means (lr) the input of which is connected to said pair of supply lines and the output of which supplies said means used in said interface means, and third (69) means display for signaling the supply of said interface means (l (> C)  11. System according to claims 2 to li, characterized in that said interface means are produced with integrated circuits implemented according to the CMS technique of "mounting the components on the surface".  12. The system as claimed in claim 11, characterized in that said interface means are located in a housing (40) comprising a first connector (42) to said parallel port, a second connector (41) to said printing means, a communication cable (43) comprising said communication bus, an external DC power outlet (47) and light-emitting diodes (44, 45, 46; constituting said display means.  3. System according to claims i to 12, characterized in that said communication lines, said input lines and said output lines are respectively the number de.quatre and in that at most sixteen microcomputers can be connected to said bus Communication.