FR2780227A1 - DATA TRANSMISSION METHOD AND DATA TRANSMISSION SYSTEM THEREFOR, AND SUITABLE OUTPUT UNIT THEREFOR - Google Patents

Abstract

Method of data transmission between at least one input unit (2 to 4) connected to a bus system (1) and at least one output unit (5, 6) connected to the bus system (1) at least one external state which can be input via the input unit (2 to 4) and at least one external control instruction which can be output via the output unit (5, 6), the input unit (2 to 4) being cyclically requested by a bus control unit (7) connected to the bus system (1) and then transmitting the external state to the bus control unit (7) .

Description

i 2780227 Data transmission method and data transmission system

  corresponding data. The present invention relates to a method for transmitting data between at least one input unit connected to a bus system and at least one output unit connected to the bus system, at least an external state which can be entered via the input unit and at least one control instruction which can be output via the output unit, - the input unit being cyclically stressed by a bus control unit connected to the bus system and the external state then being transmitted to

the bus control unit.

  The invention also relates to a data transmission system, comprising at least one input unit connected to a bus system, at least one output unit connected to the bus system and a control unit for bus connected to the bus system, - at least one external state which can be entered via the input unit and at least one external control instruction which can be entered via the output unit, - The input unit being urged cyclically by the bus control unit

  and the external state then being transmitted to the bus control unit.

  The invention also relates to an output unit which can be connected to a bus system, for outputting an external control instruction. A transmission method of this kind and the corresponding data transmission system are known for example under the designation AS-i (= actuator-sensor-interface). We also know a unit of

output by AS-i.

  In AS-i, units connected to a serial bus system are cyclically requested by a bus control unit. If the unit

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  requested is an input unit, external states are entered and forwarded to a higher rank calculation unit than the bus control unit, for example to a stored program system. The higher ranking calculation unit then determines the external control instructions to be output which it retransmits to the bus control unit. The latter then transmits it to

the output unit.

  The system described at the beginning of this memo already works very reliably. The processing of the external states entered in the higher ranking calculation unit however requires time. An immediate exit

  o external control instructions are therefore not possible.

  The present invention aims to provide a data transmission method and the corresponding data transmission system so that immediate output of an external control instruction is possible. For the data transmission method and the data transmission system, this is achieved by the fact that the output unit monitors the external state transmitted by the input unit to the bus control unit and

  issues the external command instruction according to the spied external state.

  Consequently, the output unit is designed to monitor at least one external state transmitted cyclically by an input unit which can be connected to the bus system to a bus control unit which can be connected to the bus system and to transmit a order instruction

  external depending on the external state spied on.

  According to an advantageous improvement of the data transmission method according to the invention, - at least one control bit is added by the input unit to the external state transmitted to the bus control unit, the instruction of external control may alternatively include secure content or unsafe content and - the output unit issues the external control instruction having secure content if the control bit has remained unchanged after a period of time has elapsed.

predetermined monitoring.

  According to an advantageous improvement of the data transmission method according to the invention, the input unit alternates the control bit each time the external state is transmitted to the bus control unit. According to an advantageous improvement of the data transmission method according to the invention, the bus control unit 7 addresses the units connected to the bus system according to a series of predetermined addresses, the output unit monitors that the addresses sent by the bus control unit coincide with the predetermined address sequence and - the output unit issues the control instruction having the safe content if the unit

  bus control lo deviates from the predetermined sequence of addresses.

  According to an advantageous improvement of the data transmission method according to the invention, the bus system is made in

serial bus system.

  According to an advantageous improvement of the data transmission method according to the invention, several input units can be connected to the bus system and the input unit or the input units for which the output unit can be configured monitors the external state transmitted to unit 7

  control. The invention also relates to an output unit.

  An output unit according to the invention is an output unit which can be connected to a bus system, used to monitor at least one external state transmitted cyclically by an input unit which can be connected to the bus system to a control unit bus that can be connected to the bus system and used to output an external control instruction in

depending on the external state being watched.

  According to an advantageous improvement of the output unit according to the invention, - the external control instruction may alternatively include secure content or non-secure content, it includes a timer for monitoring the flow of a predetermined monitoring duration and - it issues the external control instruction with secure content if a control bit added by the input unit to the external state transmitted to the bus control unit has remained unchanged after the monitoring time has elapsed . According to an advantageous improvement of the output unit, the output unit monitors only addresses sent by the control unit

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  coincides with a sequence of predetermined addresses and outputs the control command with safe content if the bus control unit deviates from the

series of predetermined addresses.

  According to an advantageous improvement of the output unit, several input units can be connected to the bus system and it is possible to configure for which input unit or for which input units the unit

  output monitors the external state transmitted to the bus control unit.

  In industrial automation systems and machines, dangerous states must be identified in a safe manner and the plant or machine controlled must in such a case be changed to a safe state. In order to transmit security-relevant signals, systems are most often used in the state of the art.

  specific detection, wiring and operation.

  The use of specific detection systems, cabling and operations requires, in particular, great complexity of cabling and conceals the danger of incorrect cabling. This is why there are efforts to also transmit safety related signals via a bus system. However, the security and reliability of data transmission by a data transmission system must not be jeopardized.

buses like that.

  Safety signals could certainly be transmitted via a separate bus system, which is safe from errors. But this goes against the general tendency to minimize the

wiring complexity.

  If at least one control bit in the external state transmitted to the bus control unit is added by the input unit, if the external control instruction can alternatively include safe content or non-safe content safe and if the output unit issues the external control instruction with safe content if the control bit has remained unchanged after a predetermined monitoring time has elapsed, even safety signals can, without affecting the security, be transmitted by

  through the bus system - which is not secure in itself.

  Therefore, the output unit is a safe output unit if it has a timer for monitoring the flow of a prescribed monitoring time and outputs the external control instruction with safe content.

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  if a control bit added by the input unit in the external state transmitted to the bus control unit has remained unchanged after the monitoring time has elapsed. The input unit is cyclically requested by the bus control unit. We therefore ensure that the control bit is alternated in time, especially if the input unit alternates the control bit with each transmission.

  from the external state to the bus control unit.

  If the bus system is implemented as a serial bus system, the

  wiring complexity to connect the units is minimum.

  If it is possible to connect several input units to the bus system and configure for which input unit or which input units the output unit monitors the external state transmitted to the bus control unit, the

  structure of the bus system is not subject to any kind of limitation.

  Additional advantages and features stand out

  of the description which follows of an exemplary embodiment. In the drawings, in a

  presentation of the principle: FIG. 1 represents a data transmission system, FIG. 2 represents an input unit and

  Figure 3 shows an output unit.

  In FIG. 1, a data transmission system consists of a bus system 1 and of units 2 to 7 connected to the bus system 1. Units 2 to 4 are input units. Through them, at least one external state of a technical installation can be entered each time. Units 5 and 6 are output units. Through them, at least one external control instruction intended for the technical installation can be output. Unit 7 is a bus control unit. It controls the data transmissions via the bus system 1. The bus system 1 is in this case a serial bus system. However, it could in principle also be implemented in a parallel bus system. The technical installation 8 can be of any kind. For example, technical installation 8 is a freight elevator or

a news.

  The bus control unit 7 cyclically controls, leaving the corresponding addresses, via the bus system 1 the remaining units 2 to 6 connected to the bus system 1 and then exchanges data with the unit 2 to 6 requested. If the unit 2 to 6 requested is a

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  input unit 2 to 4, the requested unit, for example the input unit 2, transmits the external state associated with the bus control unit 7. The bus control unit 7 then retransmits the external state to a higher ranking calculation unit 9. The unit 9 for calculating a higher rank may for example be a programmable controller. The higher ranking calculation unit 9 determines from the external states external control instructions which must be output via the output units 5 and 6 intended for the technical installation 8. It transmits the external control instructions to the bus control unit 7 which then retransmits them to the units 5 and 6 of

o exit.

  This process corresponds to the traditional data transmission in the AS-i protocol. To obtain a faster reaction from the technical installation 8 to states which have changed, the output units 5 and 6 are made so as to directly spy on the external states that the input units 2 to 4 transmit to the unit 7 of bus control, to operate them themselves and then to output their associated external control instruction as a function of the monitored external state. The output units 5 and 6 do not have to be called upon at all by the bus control unit 7. It is certainly possible that the bus control unit 7 requests the output units 5, 6, but this is not necessary. This is why in particular there is no need of addresses for the output units 5, 6. All available addresses can therefore be occupied by input units 2 to 4. We can therefore realize for the same transmission complexity a transmission system

larger data.

  In the output units 5, 6, it is of course possible to configure for which input unit or for which input units these output units monitor the external state transmitted to the bus control unit 7. The output unit 5 can thus for example be configured so as to only spy on the external states transmitted by the input unit 2, while the output unit 6 can be configured so as to only spy on the external states transmitted by the input units 3 and 4. To this end, one can enter the output units 5, 6 the addresses for which they must spy on the external states transmitted by the input units 2 to 4 and to which external states then transmitted they must react.

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  The output units 5, 6 therefore monitor each address sent by the bus control unit 7. If the address sent coincides with the address given to them, they monitor the external states transmitted by the input unit 2 to 4 requested and react immediately according to the external states transmitted. This can be done by the data transmission method and system described above and by the output unit 5, 6 made as a result of normal data transmissions, which are not security related. If data must be transmitted via bus system 1

  0o related to security, additional measures are necessary.

  In particular, safety-related input and output units must be designed with at least two channels. This is generally known by specialists. We will not go into more detail on this in the following. In addition, data transmission between the input units and the safety-relevant output units, designed at least in two channels

  (or at least present in duplicate) must be safe.

  In order to be able to ensure the transmission of secure data of this kind, an input unit relating to security, for example an input unit 3, comprises, according to FIG. 2, an interface module 10. The interface module 10 is connected on the one hand to the bus system 1, on the other hand to an element

  1 at the entrance to the technical installation and thirdly at a 12D scale.

  The flip-flop 12D comprises, as is generally known, a clock input 13, an input 14D and an output 15Q. The interface module 10 adds to each transmission of the external state, therefore of the connection state of the input element 11, to the bus control unit 7 the state of the flip-flop 12D as bit control. It then controls the clock input 13 of the flip-flop 12D. As the output 15Q is back-coupled in logic inversion on the input 14D, the flip-flop 12D therefore changes its internal state. On the next transmission of the external state, the control bit therefore has the opposite value. It therefore alternates with each transmission of the external state

to the bus control unit 7.

  According to the AS-i protocol, the interface module 10 always transmits four useful bits to the bus control unit 7. It can thus be

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  transmitted a maximum of three external states and the control bit to unit 7 of

bus control.

  The safety-relevant output unit 7, for example the output unit 6 shown in FIG. 3, monitors the external state transmitted by the input unit 3 to the bus control unit 7 and the control bit. The external state is used directly in an interface module 10 'and sent to a gate 16 AND. The output signal from door 16 AND then controls for example a switch 17 by means of which the technical installation 8 is separated from a current supply 18. The separation of the technical installation 8 from Io the current supply 18 therefore represents an external control instruction with safe content, the connection to the current supply 18 therefore represents

  an order instruction with unsafe content.

  To ensure correct data transmission via the bus system 1, the interface module 10 ′ sends the added control bit to a stopwatch 19. The stopwatch 19 monitors the flow of a predetermined monitoring duration. The timer 19 is reset when the control bit has changed compared to the control bit previously transmitted to the associated output unit (for example 6), therefore

  each time the control bit alternates.

  As long as the monitoring time has not yet elapsed, the chronometer sends a signal 1 to gate 16 AND, so that the output signal from gate 16 AND depends on the output signal from module 10 'd 'interface. As the associated input unit, for example the input unit 3, is called up cyclically by the bus control unit 7, the timer 19 is therefore reset, in the event of transmission of correct data, always before the end of the monitoring period. If, on the other hand, the data transmission via the bus system 1 is disturbed or if the corresponding input unit (for example 3) is disturbed, the monitoring time elapses. If, after the monitoring time has elapsed, the control bit has remained unchanged, the timer 19 sends a signal 0 to gate 16 AND. The output signal from gate 16 AND also becomes 0. Technical installation 8 is separated from the power supply

  18 once the monitoring time has elapsed and therefore goes to a safe state.

  An unsafe state of the technical installation is prevented from

produce.

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  The bus control unit 7 addresses all the units 2 to 6 connected to the bus system 1 (insofar as they can be addressed) according to an increasing sequence of addresses. The sequence of addresses is therefore predetermined. This property of the data transmission system can be used to increase the security of data transmission. The output units 5 and 6 can in fact thus monitor in addition to the alternation of the control bit also the addresses sent by the bus control unit 7 and issue the command instruction with safe content if

  the bus control unit 7 departs from the series of predetermined addresses.

  o10 They can thus bring the technical installation 8 to a safe state also in the event of "blocking" of the bus control unit 7 at the address which

is addressed to them.

  In addition, the output module 5, 6 further includes a programming interface. The programming interface 20 can for example be a base for an EPROM. Alternatively, it is also possible to use an interface with a programming unit. By means of the programming interface, it is possible to configure for which input unit, for example the input unit 3, the output unit (for example 6) monitors the external state transmitted to the unit 7 of

  bus command (if applicable including the control bit).

  By transmitting the data described above, it is therefore possible to transmit both safety-related signals and non-safety-relevant signals via a bus system designed in a non-redundant manner. In addition, it can be carried out in a simple manner

  several signal circuits without mutual influence.

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Claims (16)

  1. Method for transmitting data between at least one input unit (2 to 4) connected to a bus system (1) and at least one output unit (5, 6) connected to the bus system (1), - at least one external state which can be entered via the input unit (2 to 4) and at least one external control instruction which can be entered via the input unit (5, 6) output, - the input unit (2 to 4) being cyclically requested by a bus control unit (7) connected to the bus system (1) and then transmitting the external state to the unit (7 ) of bus control, characterized in that the output unit (5, 6) monitors the external state transmitted by the input unit (2 to 4) to the bus control unit (7) and exits the external control instruction as a function of the monitored external state. 2. Data transmission method according to claim 1, characterized in that - at least one control bit is added by the input unit (for example 3) to the external state transmitted to the unit (7) bus control command, - the external control instruction which may alternately include secure content or non-secure content and - the output unit (for example 6) outputs the external control instruction with secure content if the control bit remained unchanged after one   predetermined monitoring time.   3. Data transmission method according to claim 2, characterized in that l l 2780227 the input unit (for example 3) alternates the control bit with each transmission   from the external state to the bus control unit.   4. Data transmission method according to claim 2 or 3, characterized in that - the bus control unit (7) addresses the units (2 to 6) connected to the bus system (1) according to a series of predetermined addresses, - the output unit (5, 6) monitors that the addresses sent by the bus control unit (7) coincide with the series of predetermined addresses and - the output unit (5, 6) outputs the command statement with safe content if   the bus control unit (7) departs from the series of predetermined addresses.   5. Data transmission method according to one of the claims 1 to 4, characterized in that   the bus system (1) is implemented as a serial bus system (1).   6. Data transmission method according to one of the claims I to 5,   characterized in that it can be connected to the bus system (1) several input units (2 to 4) and in that it can be configured for which input unit (for example 2) or for which units (3, 4) input unit (5, 6) of   output monitors the external state transmitted to the bus control unit (7).   7. Output unit which can be connected to a bus system (1), for monitoring at least one external state transmitted cyclically by an input unit (2 to 4), which can be connected to the bus system (1) , to a bus control unit (7), which can be connected to the bus system (1), and to output an external control instruction depending on the state external spied.   8. output unit according to claim 7, characterized in that the external control instruction may alternately include safe content or unsafe content, - the output unit comprises a timer (19) for monitoring the flow of '' a predetermined monitoring time and - the output unit outputs the external control instruction with safe content if a control bit added by the input unit (for example 3) in the external state 4 12 2780227   transmitted to the bus control unit (7) remained unchanged after   elapsed monitoring time.   9. output unit according to claim 8, characterized in that the output unit (5, 6) monitors that addresses sent by the bus control unit (7) coincides with a series of predetermined addresses and exits the control command with safe content if the bus control unit (7) deviates from the series of predetermined addresses. 10. output unit according to claim 7, 8 or 9, characterized in that it can be connected to the bus system (1) several input units (2 to 4) and in that it can be configured for which input unit (for example 2) or for which input units (3, 4) the unit (5, 6) of   output monitors the external state transmitted to the bus control unit (7).   11. Data transmission system, consisting of at least one input unit (2 to 4) which can be connected to a bus system (1), of at least one output unit (5, 6) which can be connected to the bus system (1) and a bus control unit (7) connected to the bus system, - at least one external state which can be entered via the unit (2 to 4) input and at least one external control instruction that can be output via the output unit (5, 6), - the input unit (2 to 4) being cyclically requested by the unit ( 7) for bus control and then transmitting the external state to the bus control unit (7), characterized in that the output unit (5, 6) monitors the external state transmitted by the unit ( 2 to 4) input to the bus control unit (7) and exit the external control instruction by depending on the external state being watched.   12. Data transmission system according to claim 11, characterized in that - at least one control bit is added by the input unit (for example 3) in the external state transmitted to the unit (7) bus control command, - the external control instruction which may alternatively include secure content or unsafe content and AT 4 13 2780 227   - the output unit (for example 6) outputs the external control instruction with secure content if the control bit has remained unchanged after expiration of a   predetermined monitoring time.   13. Data transmission system according to claim 12, characterized in that the input unit (for example 3) alternates the control bit at each transmission   of the external state to the bus control unit (7).   14. Data transmission system according to claim 12 or 13, characterized in that - the bus control unit (7) addresses the units (2 to 6) connected to the bus system (1) according to a series of 'predetermined addresses, - the output unit (5, 6) monitors that the addresses sent by the bus control unit (7) coincide with the series of predetermined addresses and - the unit (5, 6) output outputs the command statement with safe content if   the bus control unit (7) departs from the series of predetermined addresses.   15. Data transmission system according to one of the claims 1 to 14, characterized in that   the bus system (1) is implemented as a serial bus system (1).   16. Data transmission system according to one of the claims 11 to 15,   characterized in that several input units (2 to 4) can be connected to the bus system (1) and that it can be configured for which input unit (for example 2) or for which units ( 3, 4) input the output unit (5, 6) monitors the external state   transmitted to the bus control unit (7).