Circuit enabling external devices to communicate with central/decentralised data processing system by means of a bus

Translation of description of equivalent WO 9749017 A1

Circuit for interfacing external devices with a centralized / decentralized data processing system via a bus

The invention relates to a circuit for Kommunika¬ tion of external devices to a central / remote data processing system via a bus after Oberbe¬ handle of claim 1.

Such circuits are used for example in process technology to external devices, beispiels¬ as "intelligent" sensors and actuators to be connected to a centralized or decentralized monitoring and regulatory anläge. In this case, both the supply of the external device, the so-called Feldge¬ chine, as well as the transmission of the received or emitted by the field device data by means of a bus, the so-called field bus, take place. As fieldbus systems, for example, m the Sensortech¬ nik HART are (Highway Addressable Remote Transmitter), the DIN-Meßbus, the PROFIBUS (PROCESS FIELD BUS), FIP (Flux Information Processor or Factory Instrumentation Protocol), the IEC fieldbus and more consistently. The transmission of the data through the buses is done partly in binary, for example, via standardized digital signals, partly analog. For example, the data transmission through the PROFIBUS is binar BE DONE while at HART the measured value is passed on analog with a superimposed amplitudmodulierten communication signal to the data processing system.

The selection of the bus system used and the materials used bus protocol is directed here primarily to the field devices used, and vice versa. Here, it is disadvantageous that the field devices must always be matched to a ver¬ wendetes fieldbus system. This means that only a certain type of field devices can be used when specifying a field bus system. So for example it is not possible to field devices that are not compatible with the bus system used, but prove to m any other way for the measuring to be advantageous also to use. Conversely, should be replaced by measuring a change in the bus system all already vorhande¬ NEN field devices, enabling communication with the newly employed bus system.

For these reasons, the flexibility of known circuits for interfacing external field devices to a central monitoring and control system is about severely restricted a field bus, whereby the efficiency of the circuit as a whole is limited.

The object of the invention is, therefore, a generic circuit for interfacing external devices with a centralized / decentralized data processing system via a bus, preferably for communication external Feldge¬ councils with a monitoring and control system via a fieldbus for use in sensor and Aktortech- nik, to further improve that any external field devices can be used independently of the existing data / Ver¬ sorgungsbussystem (field bus system) and connected to a monitoring and control system. When connecting an external device to a field bus to a particular detection of the bus system and the bus protocol and an automatic adjustment of the field device to the bus system and the bus protocol by the circuit are possible.

This object is in a circuit for Kommunika¬ tion of external devices with a central Datenverarbei¬ treatment plant according to the invention achieved by the features of the characterizing part of claim 1 by a bus with the features of Oberbe¬ handle of claim 1.

it that the circuit is Schalt¬ circuits to connect the external device to automatically detect to which bus system, such being particularly advantageous. B. HART, DIN Meßbus, PROFIBUS, FIP, Fieldbus IEC, and the like, and to automatically adjust to the bus system includes. This allows any external devices to any kind of common in the sensor and actor data / Supply bus (fieldbus systems) are coupled.

With regard to the formation of these circuits for the automatic recognition of the bus system the underside most diverse embodiments are conceivable.

For example, advantageously a processing include Buserkennungs- and adaptation sungsschaltkreise emheit m form of a processor (microcontroller, DSP and the like.) Or an ASIC for exchange and Ver¬ processing the output from the external device data and for the detection and selection of used bus system, a connector unit (MAU) for matched filtering and amplification of the received by the bus input signals and converting m digital, the microcontroller via a modem deliverable signals and adapted Ver¬ strengthening of the microcontroller output via the modem to the bus signals, the Anschaltemheit adapted a controllable power source / current sink for matching to the current / voltage source of the external device and for internal power / voltage supply to the entire Schal¬ device, one via the modem controllable by the microcontroller summing amplifier for the output of the external device and the bus Kommunikat10ns- signals and to control the current source / current sink, has.

In addition, circuits are provided to protect the circuit Übertrager- which allow galvanic isolation of the current / voltage supply of equipment connected to circuitry external device (sensor, actuator) to ensure explosion protection. for galvanic isolation of the circuit of the external device Further finds (sensor circuit) of the comparison LONG- / communication circuit of the circuit, ie to make the circuit intrinsically safe, the data transmission from the external device to the microcontroller via a digital interface, preferably a galvanic ¬ cally decoupled I²C bus instead.

It is advantageous also in that the circuit the use of bus systems allows, based on both a digita¬ len as well as an analog data communication. Also as far as the applicability any different external devices is ensured.

The following description of preferred embodiments of the invention Ausführungs¬ serves in conjunction with the drawing beiliegen¬ of clarifying. Show it:

1 schematically shows an inventive circuit for interfacing external devices with a central data processing unit via a bus. FIG. 2 shows the detailed structure of FIG. 1 darge presented circuit and FIG. 3 schematically shows the circuit diagram of external Gerä¬ th, which are coupled to a central Datenverarbeitungs¬ plant known per se on underside different buses.

In Fig. 3 is a schematic representation of a central data processing system 1 is shown to which known to to way more different external field devices 2, for example, sensors or Actuators are coupled via different fieldbuses. 3

The field devices can be 2 connected to the data processing system 1 directly through the fieldbus 3, but it can also buy several field devices 2 initially via a field distributor 4, which may be a multiplexer, for example, be connected with this field distributor 4 for its part via a fieldbus 3 with the data processing system 1 communicates. The data processing system may also by a Programmable circuit (PLC), a process control system (PCS), a personal computer (PC) or a so-called hand-He1d Terminal (HHT) to be realized.

When using several different field devices 2, each requiring a different fieldbus system 3, must be provided for their connection to the data processing system 1, different types of field buses. 3 If these different types, for example, HART or PROFIBUS, etc.. do not exist, so it is not possible to make a data connection between external devices that require this type of bus, and the data processing system 1 of the existing buses. 3

The basic idea of ​​the invention is to provide a circuit which can independent of the fieldbus system recognize the corresponding bus protocols and make the necessary adjustments so that the field device 2 at any fieldbus system 3 as without external measures operation of switches o. The like. can be coupled and thus independent of the respective fieldbus system used 3 usable. As seen in Fig. 1, m is a circuit for interfacing external devices 2 with a central data processing system 1 via bus 3 schematically shows the circuit essentially comprises a processing unit, for example a Mikrocon¬ troller 6, current / voltage supply circuits 7 and a display. 8

The external field devices 2, for example, pH sensors, conductivity sensors, etc.. be that even m without explosion hazard prone environments can be arranged both m explosive as.

For use in potentially explosive environments, the entire circuit is intrinsically safe. This requires that both the current / voltage supply of the external devices 2 by the current / Spannungsver- sorgungsschaltkreise 7 and the data exchange of the data acquired from the external devices 2 with the microcontroller 6 via circuits 5 takes place, the galvanic decoupling allowing the external device 2 of the current / voltage supply circuit 7 and the microcontroller 6th

The circuit for interfacing external devices 2 by means of a central data processing unit 1 via a bus 3 detail m Fig. 2 is shown.

As is apparent from Fig. 1 and Fig. 2, circuits 5 are provided to ensure the intrinsic safety of the circuit.

Filtering and surge protection circuits 11 ermögli¬ under not only a means of filtering the example a fed in a conventional two-wire power and data signals, but they also ensure that no interference voltages / currents out of the circuit can get to the data bus 3; Thus they allow the use of the entire circuit m exp1oslver environment.

The input signals are first on the circuits 5 and the filter and high-voltage protection circuits 11 a Anschaltemheit (. MAU, English Medium Attachment Unit) supplied 12 carries. This Anschaltemheit 12 is used for filtering the input / output signals, in the case of analog signals, for converting said m digital signals.

From the Anschaltemheit 12, the signals pass through a modem 14 to the microcontroller 6 which is connected, for example with an external key pad 16 as well as with the display 8 or with an EEPROM 20 via connecting lines. The microcontroller 6 is - decoupled via a digital interface 17, for example, an I²C-bus 17 - connected to a transmitter 22, via the one of pH, temperature, conductivity measurement, or the like. by means of a (not shown) sensor.

The Anschaltemheit 12 further comprises a controllable current source or sink 12a to adapt to the current / voltage conditions of the controllable device and the internal current / voltage supply of the entire circuit.

Further, in the Anschaltemheit 12 a of the micro-controller 6 via the modem 14 controllable summing amplifier 12b to output to the external Device and the bus adapted communication signals and to control the current source / current sink 12a seen vor¬.

The circuit automatically detects the existing at its input bus and makes an adjustment of the external field device on that bus. 3

It is for example possible by means of the circuit, to recognize a digital transmission of data, such as is present for example in the PROFIBUS same and process, such as an analog data transmission, such as is customary for example in the known HART bus.

This raises the circuit after it has detected by the connection unit 12 of the modem 14 and the microcontroller 6 and the controllable current / voltage supply circuit which bus 3 at the input, independently one of the voltages necessary for the different bus systems - for example, a current value between 4 and 20 mA, depending on the measured value, in case of using the HART bus, or to the corresponding current and voltage values ​​of the digital signal transmission in the case of PROFIBUS.

Finally it should be mentioned that the connector unit 12, the modem 14 and the microcontroller can also be part of a single integrated circuit.