FR2724470A1 - Electronic card for emulating magnetic tape memory - Google Patents

Abstract

The tape emulator card has a memory with a defined communication interface. The interface has a data line (LDo, LDi) to deliver data in a first known format, a number of control lines (LC) to apply control signals to the memory, and a set of status lines (LE) to carry status signals from the memory. An electronic interface card (1) couples the memory to the host system through a bus (B) conforming with a standard defining a second data format. The interface card has a programmable controller (2) connected to the interface circuits to control access to data stored on the memory card, and to transport the data from the card to a standard tape interface.

Description

ELECTRONIC PROCESS AND CARD
TO EMULATE A MAGNETIC BAND MEMORY.

The invention relates to the field of computer systems and relates more particularly to systems using magnetic tape memories, also called reader-recorders or unwinders of magnetic tapes.

This type of memory, the recording medium of which is most often in the form of a removable cassette, is in particular used to save operating data from various installations. The acquisition of this data is carried out by a host system connected to the memory and which controls their recording throughout operation. This stored data can then be analyzed with a view, for example, to improving the operating process or looking for the cause of possible failures.

Such data acquisition and backup systems are for example used in warships. The data recorded during navigation is kept on shore for analysis or to carry out simulations used for the training of cabin crew.

In such a context, it is essential that the computers and the magnetic tape memories used on board are compatible with those located on land. The simplest solution, which consists of using identical equipment on board and ashore, however, comes up against the problem of modernizing the equipment. It is necessary to plan sooner or later to replace old equipment with newer equipment, particularly since the maintenance of old equipment may no longer be ensured. This replacement must be able to be carried out gradually, while ensuring interoperability between recent and old equipment. Furthermore, the cost involved should be as low as possible.

The modernization of computers located on land is the least difficult, especially since they do not have to be militarized. The problem is then to allow data exchanges between new generation computers and magnetic tape memories. For cost reasons, we will preferably choose computers conforming to one of the market standards. As the old materials are generally incompatible with these standards, it will therefore be necessary to design a specific coupler capable of converting the formats of the data exchanged and of adapting the communication protocols imposed respectively by the magnetic tape memory and the computer.

We can advantageously exploit the greater power of recent computers by increasing the number of connectable memories. It is also possible to provide a coupler capable of managing several memories with the possibility of connecting several couplers to the same computer.

With a view to further modernization, there is also the problem of replacing magnetic tape memories by more modern and less expensive memories such as magnetic disk or magneto-optical memories. As before, it is necessary to maintain the interoperability between the new memories and the old computers on board the ships or on shore. This requires an interface unit capable of communicating with the new memory so as to emulate the magnetic tape memory. One solution would therefore consist in designing an emulation card functioning as a coupler for example between a magnetic disk memory and the interface of old computers.

As this type of memory normally uses the so-called "SCSI" link which is the standard interface for peripherals, the emulation card should therefore adapt the SCSI interface to the interface of older computers.

The object of the invention is to produce a magnetic tape memory emulator at a lower cost than that of the previous solution.

To this end, the subject of the invention is a method for producing an emulator of a magnetic tape memory, said memory being adapted to a communication interface defined in particular by - at least one data line for conveying data according to a first determined format, - a first number of command lines for applying corresponding control signals to the memory, - a second number of state lines for receiving corresponding state signals from the memory, said method being characterized in that 'It consists of a) producing an electronic card capable of operating as a coup between said memory and a host system via a computer bus conforming to a determined standard which defines a second data format, said card comprising a unit programmable control unit connected to interface circuits allowing the unit to communicate with said bus, means for transferring data controlled by the control unit, connected to said interface circuit and making it possible to exchange data between said interface and said bus in accordance with said first and second formats respectively, a parallel output circuit connected to the control unit and having output and input terminals for respectively providing transmit signals and receiving receive signals, the number of said output terminals and the number of said input terminals each being at least equal to the largest of said first and second numbers, the operation as a coupler of said card being carried out by means of a first program executed by the control unit, said control signals being supplied by at least part of the output terminals and at least part of the terminals input receiving said status signals, b) connecting said card via said bus to a memory system comprising a controller adapted to udit bus, c) installing in the control unit a second program designed to cooperate with said controller and operate the card as an emulator of the magnetic tape memory, at least part of the output terminals providing said status signals and at least part of the input terminals receiving said control signals.

The interest of this solution lies first in the fact that the realization of the emulator does not imply the complete development of a specific card. The cost of development is in fact limited to that of designing the program which performs the emulator function of the card. Furthermore, the manufacture of couplers and emulators involves the manufacture of a single type of electronic card, which also leads to a reduction in costs.

The choice of a standardized bus, such as the VME bus, will therefore make it possible to use processor cards which are very widely marketed and of low cost. There are, for example, MVME 147 or MVME 162 cards sold by the company MOTOROLA and which can be configured in central units managed for example by the UNIX operating system (registered trademark).

With another configuration using an embedded program, the same card with a memory extension can be used as a device controller. Thus, the same type of processor card can be used to constitute a host system associated with a coupler card or else a disk memory controller associated with an emulation card. As the processor cards are normally provided for ensuring the management of the system bus and carrying out the initialization operations of the other units of the bus, the invention proposes to exploit this possibility. Also, the method according to the invention is further characterized in that said bus is managed by the host system or by the controller, in that for data transfer operations via the bus, said first program is provided to operate said card in slave mode vis-à-vis the host system and in that said second program is provided to operate said card in master mode vis-à-vis the controller.

In order to facilitate maintenance and inventory management, it is particularly interesting that the emulator card and the coup card are completely trivialized. For this, and according to another characteristic of the invention, the first and second programs are permanently installed in a program memory of the control unit and in that the selective activation of one of said first and second programs is carried out by means of initialization programs provided respectively in said host system and said controller.

Other aspects of the method according to the invention relating more particularly to the connection problems will be explained in more detail in the following description.

We previously mentioned the possibility of making a coup card which can be connected to a plurality of magnetic tape memories. It is then possible to use this structure to perform the emulator function without the need to provide additional inputs and outputs of the parallel input-output circuit.

For this and according to another aspect of the invention, the card is used to emulate a number of magnetic strip memories less than the number of readers that the card can connect to the host system when it operates as a coupler, so as to have 'a sufficient number of input and output terminals to allow said emulation.

The invention also relates to an electronic card allowing the implementation of the process which has just been described. The card is characterized in that it comprises a programmable control unit connected to interface circuits allowing the unit to communicate with said bus, data transfer means controlled by the control unit, connected to said circuit interface and allowing data to be exchanged between said interface and said bus in accordance with said first and second formats respectively, a parallel input-output circuit connected to the control unit and comprising output and input terminals for respectively providing transmit signals and receiving receive signals, the number of said output terminals and the number of said input terminals each being at least equal to the largest of said first and second numbers.

Other aspects and advantages of the method and of the electronic card according to the invention will appear in the following description with reference to the figures.

- Figure 1 shows a configuration of an old system with two magnetic tape memories.

- Figure 2 shows a configuration of a system using an electronic card operating as a coupler between a new host system and two magnetic tape memories.

- Figure 3 shows a configuration using a central unit of an old system associated with a magnetic stripe memory emulator produced according to the invention.

- Figure 4 is a diagram of an embodiment of an electronic card according to the invention.

- Figures 5 to 7 show several possibilities of wiring for the implementation of the method according to the invention.

FIG. 1 schematically represents an example of an old system to which the invention can be applied.

In the configuration shown, a central unit SO of a host computer is connected to two magnetic tape memories LO, L1. The central unit SO is of course associated with other peripherals not shown. The connection between the central unit and each memory is carried out by means of connectors and wiring materializing the communication interface.

In the example shown, the central unit and the readers are removably mounted and for this are provided with male connectors, such as the connectors K3 of the memories, so that they can be plugged into female connectors K2 to which a backplane wiring. As shown, the memories can also be in the form of boxes of predefined dimensions so as to be integrated in computer cabinets.

FIG. 2 shows a system where the central unit SO is replaced by the assembly consisting of a coupler 1 linked to a host system S1 via a standardized bus B. The coupler 1 consists of a card electronics according to the invention, a more detailed description of which will be given later.

As in the case of FIG. 1, the coupler 1 is connected to the readers LO, L1 by means of connectors K1,
K2, K3 and LK wiring supporting the IF interface.

The host system S1 may consist of one or more processor cards adapted to the bus B itself connected to various peripherals by means of corresponding adaptation cards.

The configuration shown in FIG. 3 corresponds to the case where a central unit SO of the old system is connected to an emulator EL of a magnetic tape memory LO or L1. The EL emulator consists of an electronic card in accordance with the invention connected to a memory system SM via the standardized bus B. The memory system SM essentially consists of a mass memory DM, such that 'a magnetic disk, connected to bus B via a CM controller. The controller CM can be produced by means of a processor card identical to that used in the host system S1 of FIG. 2 but configured and programmed to perform the function of peripheral controller. The link between the CM card and the mass memory DM could for example use the standard SCSI link. The connectors K1 adapted to the card 1 are connected to a male connector K3 identical to that used in the readers LO, L1. The wiring that can be used for this link will be specified later in the description. Thanks to progress in miniaturization of components and magnetic disks, it will even be possible in certain cases, as shown in the figure, to group together all the elements making up the emulator so as to have a smaller footprint than that of the case of the memory of the old generation. These elements can then be mounted inside an identical box in dimensions and connections so as to be fully compatible with the cabinets of old equipment.

FIG. 4 represents the general diagram of an electronic card 1 according to the invention. The diagram shows by way of nonlimiting example the particular case of a card mounted as a coupler and adapted to a single memory. The communication interface IF between a memory L1 or L2 and the card is materialized by the external wiring lines LK made up of two mono-directional serial data lines LDo, LDi, of control lines LC for transmitting control signals SC to memory and LE status lines to transmit SE status signals from memory. The control signals SC are for example the control signals for reading, writing, rewinding, selecting the track number, rewinding or running the tape. The status signals SE are for example the signals indicating that the memory is on, that the tape is at the start or end of the track, that the memory is properly supplied, that a magnetic tape cassette is in place, etc. The interface could also include lines assigned to bi-directional signals (not shown).

Note that the number of LC command lines and the number of LE status lines are generally not equal. This situation is shown diagrammatically in FIG. 4 where the number of LC lines is less than that of LE lines.

The system bus B to which the card 1 is connected is for example a high-performance parallel backplane bus such as the VME bus, the detailed characteristics of which are described in the standard.
NF C 96-031. This bus is particularly well suited to support host systems of the UNIX type (registered trademark). In addition, there are processor cards on the market that are suitable for this standard and can be configured and programmed as the central unit of a host system and operating as a master over the bus or as a peripheral controller and operating as a slave. For more details concerning the implementation of processor cards, reference should be made to the aforementioned standard.

The card 1 comprises an interface circuit 3 connected on the one hand to the system bus B and on the other hand to an internal bus b. It further comprises a control unit 2, data transfer means 4, and a parallel input-output circuit 5, these elements 2, 4, 5 each being connected to the internal bus b. The interface circuit 3 is organized around an exchange memory 16 which can be accessed for reading and writing by the bus B and the internal bus b thanks to a data interface circuit 15 and an interface circuit of addresses 17. Circuit 3 finally comprises a bus arbitration circuit intended to resolve access conflicts. The control unit 2 is essentially composed of a microcontroller 6 provided with the direct access function to the memory ("DMA") and at least one non-volatile memory 7 intended to contain the programs executable by the microcontroller 6.

Advantageously, the memory 7 will contain the two programs PR1, PR2 respectively specific to their sound and emulator functions that can be performed by the card. In this case, the activation of one of the programs PR1 or PR2 will be carried out during the initialization phase triggered by the processor card of the host system or of the controller.

The card 1 communicates with the IF interface via a connector K1 composed of a male part fixed to the card and a female part connected to the external wiring LK.

The data transfer means 4 comprise a universal asynchronous transceiver of the UART type provided with the direct memory access (DMA) function, the essential function of which is the parallel-serial conversion of the data coming from the bus b and the serial-parallel conversion of incoming data. Depending on the data format imposed by the interface
IF, circuit 9 can also be provided with auxiliary functions such as the generation and control of parity bits or the generation of start and end delimiters of data blocks. The serial output of circuit 9 provides bursts of binary data according to the NRZ (non-return to zero) format. These data are converted by a transmission finite state machine 10 into a code suitable for the IF interface such as the code l'ysncHEsTER't. Finite state machines, hereinafter called "state machines", are programmable logic sequencers ("PLS") programmed to perform the desired functions. The signals coded by the state machine 10 are transmitted after amplification to the data line LDo via the connector K1. Conversely, the coded data received from the line LDi are transmitted to a reception state machine 11 via the connector K1 and an amplifier. The state machine 11 is provided for decoding and supplying circuit 9 with bursts of data according to the NRZ format. Circuit 9 can then extract the useful data and place them in parallel on the internal bus b.

The parallel input-output circuit 5 is responsible for transferring the control and status signals between the bus b and the connector K1. It comprises at least one integrated input-output circuit 12 of the "PIO" or "PIA" type. The circuit 12 is connected to the internal bus b. Its outputs constitute after amplification and shaping the output terminals Bo of the circuit 5. The input terminals Bi of the circuit are connected after amplification to the input lines of the circuit 12. The circuit 12 is configured and the amplifiers 13 are provided so that the number of output terminals and the number of input terminals are each at least equal to the greater of the numbers of control lines LC and status lines LE imposed by the interface IF.

The card also includes a clock circuit 8 and supply circuits not shown. The various circuits constituting the card are integrated circuits of conventional type: for example, the components PLS 168A, SCN 68562 and
SCC 68070 from PHILIPS to produce state machines 10, 11, UART 9 and microcontroller 6 respectively.

When the card 1 is intended to operate in coupler mode, the LK wiring shown in FIG. 5 is used allowing the direct connection of the connector K1 with the female connector K2 suitable for memories with magnetic strip LO or L1. Output terminals Bo are connected to the control lines LC and input terminals Bi are connected to the status lines LE. When the card is used as an emulator, the wiring shown in FIG. 6 is used according to which the connector K1 is connected to a male connector K3 with inversion of the data lines and so as to match the output terminals Bo with the lines d LE and Bi input terminals with LC control lines. We can see in the example shown that the number of output terminals Bo connected to the wiring lines is less than that of Bi input terminals in mode coupler, and vice versa in emulator mode.

The operation of card 1 in hit mode is as follows. The host system develops the orders of the operations to be carried out. These orders are transmitted to the microcontroller 6 via the bus B and the interface circuit 3. If it is a write operation, the host system places the data to be written in the exchange memory 16. The microcontroller then controls the circuit 5 so that it supplies the control signals corresponding to the operation. In response to the status signals received from the magnetic tape memory and transmitted by the circuit 5, the microcontroller controls the circuit 9 so that it proceeds in DMA mode to transfer the data contained in the exchange memory 16 to the LDo output data line via the transmission state machine 10. For a read operation, the host system informs the microcontroller 6 of the number of bytes to be read and of the track number on which find this information. The microcontroller then controls the circuit 5 so that it sends the read control signals as well as the track number on the LC control lines and positions the circuit 9 in reception mode. The data read in the magnetic tape memory pass through the input data line LDi, are decoded by the reception state machine 11 and taken into account by the circuit 9 which proceeds in DMA mode to transfer the data in parallel to the exchange memory 16 to which the host system can access.

The operation of the various circuits of the card 1 in emulator mode is entirely analogous with the difference that the program makes the card 1 master with respect to the bus B and slave with respect to the interface IF. In particular, the signals received on the input terminals Bi are interpreted by the program as control signals having the effect of triggering requests for read or write to the memory system SM. Conversely, the signals leaving the terminals Bo simulate the behavior of a magnetic tape memory. Data exchanges are carried out in the same way as in coupler mode thanks to exchange memory 16 and circuit 4. Thus, by simply changing the program executed, the card behaves like a magnetic tape memory, electronically than temporally.

FIG. 7 represents an alternative embodiment of the card 1 allowing cabling independent of the chosen operating mode to be used. According to this variant, an interconnection network 18 is provided, placed between the data, command and state amplifiers and the connector K1. The interconnection network 18 controlled by the signal EMU of the microcontroller 6 is designed to perform a function equivalent to the wiring inversions shown in FIGS. 5 and 6.

Without departing from the scope of the invention, the embodiment described above can be easily adapted to other contexts. In particular, data transmission could be bidirectional and use one or more lines. In this case, no inversion of the corresponding wiring lines would be necessary to switch from coupler mode to emulator mode.

Likewise, the card could be supplemented so as to simultaneously serve them to several magnetic tape memories. It suffices for this to provide additional connectors K1 and to consequently increase the capacity in number of terminals Bo and Bi of circuit 5. The use of the card in emulation mode can then be carried out without constraint as to the numbers of terminals Bo or Bi if we reduce the number of readers that the card can emulate.

Claims (10)

1. Method for producing an emulator (EL) of a memory (LO, L1) with magnetic tape (BM), said memory (LO, L1) being adapted to a communication interface (IF) defined in particular by - at least one data line (LDo, LDi) to convey data according to a first determined format, - a first number of command lines (LC) to apply to the memory (LO, L1) corresponding control signals (SC), - a second number of state lines (LE) for receiving from the memory (LO, L1) corresponding state signals (SE), said method being characterized in that it consists of a) producing an electronic card (1) capable of operating as a coupler between said memory (LO, L1) and a host system (S1) via a computer bus (B) conforming to a determined standard which defines a second data format, said card comprising a unit programmable control (2) connected to interface circuits (3) per putting the unit (2) to communicate with said bus (B), data transfer means (4) controlled by the control unit (2), connected to said interface circuit (3) and making it possible to exchanging data between said interface (IF) and said bus (B) in accordance with said first and second formats, respectively, a parallel input-output circuit (5) connected to the control unit (2) and comprising output terminals (Bo) and input (Bi) for respectively supplying transmission signals (So) and receiving reception signals (Si), the number of said output terminals (Bo) and the number of said input terminals (Bi ) each being at least equal to the largest of said first and second numbers, the operation as a coupler of said card (1) being carried out by means of a first program (PR1) executed by the control unit (2), said signals control (SC) being supplied by at least part of the output terminals (Bo) and at least part of the input terminals (Bi) receiving said status signals (SE), b) to connect said card via said bus (B) to a memory system (SM) comprising a controller (CM) adapted to said bus ( B), c) to install in the control unit (2) a second program (PR2) designed to cooperate with said controller (CM) and operate the card (1) as a memory emulator (LO, L1) at magnetic tape, at least part of the output terminals (Bo) providing said status signals (SE) and at least part of the input terminals (Bi) receiving said control signals (SC). 2. Method according to claim 1, characterized in that said bus (B) is managed by the host system (S1) or by the controller (CM), in that for the data transfer operations via the bus (B), said first program (PR1) is intended to operate said card (1) in slave mode with respect to the host system (S1) and in that said second program (PR2) is provided to operate said card in malta mode vis-à-vis the controller (CM). 3. Method according to one of claims 1 or 2, characterized in that said first and second programs (PRl), (PR2) are permanently installed in a program memory (7) of the control unit (2) and in that the selective activation of one of said first and second programs (PR1, PR2) is carried out by means of initialization programs provided respectively in said host system (S1) and said controller (CM). 4. Method according to one of claims 1 to 3, characterized in that the connection between the circuits of said card (1) and said interface (IF) is carried out by means of first connectors (K1) allowing in particular to connect all from said input (Bo) and output (Bi) terminals at first ends of external wiring lines (LK), in that depending on the operating mode chosen for said card (1), the other ends of said lines wiring (LK) are selectively connected to another connector (K2, K3) of a first or a second type, said other connector of the first type (K2) being identical to the connector used to connect said interface (IF) to said magnetic tape reader (LO, L1), said other second type connector (K3) being a connector intended to be connected to said first type connector (K2). 5. Method according to one of claims 1 to 3, characterized in that said card (1) is provided with an interconnection network (10) controlled by the control unit (2), connected on the one hand to said input (Bi) and output (Bo) terminals and on the other hand to the first ends of corresponding wiring lines (LK), in that said interconnection network (18) is provided for selectively connecting according to the operating mode of said card (1) said input (Bi) and output (Bo) terminals to said wiring lines and in that the other ends of the wiring lines (LK) are selectively connected to another connector (K2 , K3) of a first or second type, said other connector of the first type (K2) being identical to the connector used to connect said interface (IF) to said magnetic tape reader (LO, L1), said other connector of the second type (K3) being a connector designed to be connected to said connector of the first st type (K2). 6. Method according to one of claims 1 to 5, characterized in that in the case where the data carried by said interface (IF) use one-way data lines (LDo, LDi), the change of operating mode of said card (1) is accompanied by a permutation of said one-way data lines (LDo, LDi). 7. Method according to one of claims 1 to 6, characterized in that said card being capable of operating as a blow between a plurality of magnetic tape memories (LO, L1) and said host system (S1), said card ( 1) is used to emulate a number of magnetic tape memories (LO, L1) lower than the number of readers that the card can connect to the host system (S1) when it operates as a coupler, so as to have a sufficient number input (Bi) and output (Bo) terminals to allow said emulation. 8. Method according to one of claims 1 to 7, characterized in that said computer bus (B) is of VME type.  9. Electronic card for implementing the method according to one of claims 1 to 8, characterized in that it ccmporte a programmable control unit (2) connected to interface circuits (3) allowing the unit (2) for communicating with the bus (B), data transfer means (4) controlled by the control unit (2), connected to the interface circuit (3) and making it possible to exchange data between the interface (IF) and the bus (B) in accordance with the first and second formats respectively, a parallel input-output circuit (5) connected to the control unit (2) and comprising output terminals (Bo) and input (Bi) for respectively supplying transmission signals (So) and receiving reception signals (Si), the number of output terminals (Bo) and the number of input terminals (Bi) being each at least equal to the largest of the first and second numbers.  10. Electronic card according to claim 9, characterized in that the data transfer means (4) comprise at least one integrated circuit of the universal asynchronous transceiver type "UART" (9) so as to be able to exchange data between a system bus (B) of VME type and a communication interface (IF) conveying data in series via two unidirectional data lines of opposite direction (LDo, LDi) and in that the input-output circuit parallel (5) comprises at least one integrated circuit of the "programmable input-output" type (12).