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ARRANGEMENT FOR THE REMOTE SWITCHING-ON AND INITIALIZATION OF A DATA TERMINAL
BACKGROUND OF THE INVENTION
1. Field of the invention
The present invention relates to a data terminal with an arrangement for the remote switching-on and initialization of the terminal connected to a remote computer 10 by means of a telephone line.
2. Description of the prior art
An arrangement for connecting a terminal to a computer in the absence of the operator is kmown which uses a core memory for containing the program required for connection. In this arrangement, the call signal serves solely to produce the reply of the terminal to the computer inasmuch as the central unit and the peripheral units have already been supplied and initial- 2o ized previously.
The disadvantage of this arrangement consists in the loss of reliability of the system consequent upon the fact that all the electronic parts are continuously supplied throughout the period (generally at night) of the ab- 25 sence of the operator.
The problem therefore exists of increasing the reliability of the terminals by reducing the total number of hours during which the system is supplied.
SUMMARY OF THE INVENTION 30
According to the present invention there is provided a data terminal including an arrangement for switching on and initializing the terminal when connected to a telephone line capable of transferring signals from and 35 for a remote computer, comprising a power supply unit connectable to a voltage source and adapted to supply the circuits of the data terminal and switching control unit controlled by a manually-operable switch having a position for remote switching on of the data terminal, in 40 which position the switching conrol control is energized from the voltage source and is arranged to recognize a call signal transmitted by the remote computer on the telephone line, the switching control unit including a logical circuit which is activated by the recognition of 45 the call signal and arranged to connect the power supply unit to the voltage source and to separate a signal activating the operations of initialization of the data terminal. J0
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of a terminal using an arrangement embodying the invention;
FIG. 2 is a flow diagram of the operations of switch- j j ing-on and initialization of a terminal using the arrangement of FIG. 1;
FIG. 3 shows the switching-on control unit;
FIG. 4 is a block diagram of switching logic included in the control unit of FIG. 3; ^0
FIGS. 5 and 6 represent the contents of two registers contained in memories of the terminal;
FIGS. 7 and 8 represent a flow diagram of the operations performed by the firmware in the initialization stage; and 65
FIG. 9 is a logic diagram with the detail relating to the logic signal generated by a key in the remote switching-on position.
GENERAL DESCRIPTION OF THE INVENTION
The operation of the terminal 1 in the absence of the operator will be described with reference to FIG. 1. The terminal 1 includes a central unit CPU-7 capable of executing all the arithmetical and logical operations required by the instructions contained in a read/write memory RAM-6 on the data also stored in the memory RAM-6. A read-only memory ROM-8 contains the microprograms required for commanding the circuits of the central unit CPU-7 and executing the instructions contained in the memory RAM - 6.
A control console 9 contains the control means required by the operator and, in particular, a switching-on key 10 which has ON and OFF positions and, in a position TLA, enables the machine to be prearranged for remote switching-on from the telephone line. The console 9 is connected to a switch control unit 4 via a channel 19. The unit 4 serves to switch the terminal on by connecting a power supply unkit 5 to the mains VAC.
A printer 18, a display SO and a keyboard 11, together with the abovementioned devices, complete the basic structure of the terminal 1. The terminal 1 is connected to a remote computer 2 through a telephone line 17 and a line controller 3 which includes a modem. Peripheral units 12 to 15 constitute the possible magnetic-support units which can be connected to the terminal.
a floppy disc unit FDU-12,
a magnetic cassette unit CTU-14 and
a fixed disc unit DAS-15.
The line controller 3 and the peripheral units 12 to 15 are connected to the central unit 7 through a channel 16.
The operation of the units constituting the terminal 1 is not described in detail, since they are described in detail in our British Patent Application No. 53991/74 and corresponding to French Application No. 2,256,476 published 25.7.1975, to which reference is made. This describes a microprogrammed computer of the type used by the terminal of the present invention. The line controller 3 and the peripheral units are not described in the said patent application but are widely used in the art and are described in the specialized technical literature.
For example, in the book "Digital Storage Systems" by W. Renwick and A. J. Cole, published in 1971 by Chapman and Hall Ltd., London, chapter 4 describes the techniques of recording on magnetic supports or carriers and chapter 5 describes the selection and control circuits used. Moreover, chapters 7 and 8 refer to the thin-film memories and semiconductor memories used for the RAM-6. Finally, chapter 10 speaks of the read-only memories of the type of the ROM-8. In the book "Trasmissione dati" by E. Angeleri, published by Delfino, Milan, in 1972, paragraphs 6.4 to 6.6 explain the circuitry of the modem and of the commands which come from the line controller 3 to the modem for effecting connection with the remote computer 2. For greater detail concerning the technique of microprogramming used by the central unit CPU-7 and the line controller 3, conult chapters 2 and following of the book "Microprogramming: principle and practices" by S. S. Husson, published 1970 by Prentice-Hall Inc. This illustrates the techniques of control of the arithmetic and logic unit and of the registers constituting the CPU-7 which are achieved by means of the microinstructions recorded in the ROM-8. On the basis of the description contained in the said patent application and of the examples given in
the book by Husson, any average technician is able to write the microprograms corresponding to the flow diagrams given in FIGS. 6 and 8.
In order to prepare for operation of the switch control unit 4, the operator must perform the following 5 operations:
1. He mounts on a selected peripheral unit a magnetic support containing the programs needed by the line controller 3 for handling the conversation with the remote computer 2 and the programs for processing the 10 data received from the remote computer 2.
2. He positions the key 10 in the remote switching-on position indicated by TLA in FIG. 1.
When the signal RING arrives on the telephone line 17, the hardware/software system behaves in accor- 15 dance with the flow diagram illustrated in FIG. 2. The block 21 commands the execution of the following operations. The signal RING is recognized by the line controller 3 and sent to the switch control unit 4, which attends to the connection of the power supply 5 to the 20 supply system VAc< as will be explained in detail below. Then, the firmware (flow diagrams of FIGS. 7 and 8) attends to the loading into the RAM-6 of the initializing program SIM (= system initializing module) from the peripheral unit predetermined by a register 86 (FIG. 9) 25 contained in the ROM-8.
By means of the execution of the blocks 22 and 23, the program SIM transfers to the RAM-6 the programs of the Operative System (OS) which are required for executing the blocks 24 and 25, 24' and 25' or 24" and 25", 30 respectively, if the initializing peripheral is the unit CTU-15, DAS-15 or DCU-13/FDU-12. More particularly, the block 24 (or 24', or 24") transfers to the line controller 3 the programs required for the conversation with the remote computer 2. The block 25 (or 25' or 25" 35 ) starts the line application program. The blocks 26 and 29 are required for prearranging the loading of the program into the line controller 3 by means of the blocks 24' and 24".
The line controller 3 sends a READY signal to the 40 remote computer 2, which is interpreted as an enabling for initiating the conversation between the terminal 1 and che computer 2. The conversation is handled by the block 32, which contains the line application program. The block 33 recognizes the end of the conversation 45 and attends to the disconnection of the terminal 1 from the telephone line and moreover starts the application program which processes in the home system the data received from the remote computer 2. At the end of the processing operations specified by the application pro- 50 gram, the block 34 issues the instruction for switching off the system, which causes the disconnection of the power supply 5 from the mains supply. The system returns to the remote switching-on state in which it was before reception of the call signal RING and is there- 55 fore ready to receive further calls.
The operation of the remote switching-on arrangement of the terminal 1 will now be described with reference to FIGS. 1 and 3. In all positions other than OFF, the key 10 closes a switch 28 which supplies power to a 60 transformer 27 in the unit 4. The logical circuits 21 of the unit 4 are thereby supplied with power and the movable contacts of two further switches 29 and 31 are energised via a line 19A. In the ON position of the key the switch 29 is open and a signal UN on a line 19B is 65 absent. To switch the terminal on the key 10 has to be moved from ON to an unstable positioned (FIG. 1), from which the key returns to ON under the action of a
spring when released. In the position D the switch 30 is closed and a signal CO on line 19C is used to switch on the power supply 5 as will be described below.
In the TLA position of the key 10 the switch 29 is closed and UN is present on line 19B. In these circumstances the power supply is switched on on receipt of RING as will also be described below. In either event the power supply is switched on by energizing a pilot relay 22 to close contacts 22A, fed from the switch 28, thereby to energise a main relay 23 whose contacts 24, 25 and 26 connect the mains 31 to the power supply 5. When energised, the power supply 5 provides the d.c. voltages which are applied to the central unit CPU-7 and to all the peripherals included in the terminal 1.
The power supply 5 also emits a signal +20VE, which is sent to the unit 4 to indicate correct functioning of the power supply 5. In the event of the d.c. voltages provided by the power supply 5 not reaching the specified levels, the pilot relay 22 is deenergised and so is the main relay 23 which, in turn, removes the voltage V^cfrom the power supply 5, thus switching the terminal 1 off.
When the key 10 is ON, a fresh switching-on attempt can be made by bringing the key 10 back again to position D and releasing it into the ON position. Complete switching-off of the terminal 1 is obtained by positioning the key 10 in the OFF position.
When the key 10 is in the position TLA, the terminal 1 can be switched off by the central unit CPU-7 by the execution of a special switching-off instruction which generates a signal TERM.
Switching off by means of the signal TERM permits switching on again by means of the signal RING. The switching-off due to abnormalities of the power supply 5, that is caused by the signal +20VE, is stored by the unit 4 and blocks switching on again through the signal RING. Reactivation of the arrangement is possible only after invention by the operator, who must turn the key 10 into the OFF position and then into the position TLA again.
The operation of the switching logic 21 will now be described with reference to FIG. 4. When the supply cable 31 (FIG. 3) is connected to the mains supply VAc and the switch 28 is closed, the transformer 27 supplies the logic 21. An initial reset device 41 is activated by the local supply derived from the transformer 27 and emits a reset signal. This signal is applied to the reset input of flip-flops 38 and 35 and, through OR circuits 47 and 48, to the reset inputs of flip-flops 42 and 43. The logic 21 is now in the waiting-for-switching-on state. At this point, the sole device of the terminal 1 which is supplied with power is the unit 21. This is ready to receive the selection made by the operator by the key 10.
If the key 10 is positioned at ON and is moved to D, the closing of the switch 30 generates the signal CO which is buffered in a flip-flop 36 which, in turn, sets the flip-flop 43. The output signal of the flip-flop 43 is applied to a first input of a multiplexer 44. The second input of the multiplexer 44 is constituted by the call signal RING coming from the telephone line through a univibrator 37, the flip-flop 38, and a pulse generator 40 and the flip-flop 42.
The selecton input of the multiplexer 44 is constituted by the signal UN coming from the switch 29 via a flipflop 35. Since it is assumed that the key 10 is in the ON position, it follows that the switch 29 is open and therefore the flip-flop 35 is reset. The signal applied to the selection input of the multiplexer 44 is therefore at logi