GB2165970A

GB2165970A - Method and apparatus for an expandable remote interface unit

Info

Publication number: GB2165970A
Application number: GB08519613A
Authority: GB
Inventors: Robert E Smith; Kenneth W Gay; Kevin R Sharp
Original assignee: Burr Brown Corp
Current assignee: Texas Instruments Tucson Corp
Priority date: 1984-10-19
Filing date: 1985-08-05
Publication date: 1986-04-23
Also published as: JPS6198465A; GB8519613D0; FR2572203A1; DE3537399A1

Abstract

A remote interface unit (10) is described for providing an interface between a host data processing unit (5) and at least one remote device (16-19). The remote interface unit (10) has apparatus (3,4) for receiving digital and analog signals from the remote device and apparatus for applying control signals to the remote device (16-18). The control signals are typically determined by the status signals and the correlation can be performed either in the remote interface unit (10) or in the host data processing system (5). The remote interface unit (10) can be expanded to include removable individual modules for additional coupling to remote devices (16-18) or can be expanded by being electrically coupled to additional remote interface units (10). The remote interface unit (10) includes a plurality of checking functions. <IMAGE>

Description

SPECIFICATION Method and. apparatus for an expandable remote interface unit This invention relates generally to electronic units for providing an interface between remote devices and a host computer. In particular, the electronic interface units can acquire state signals from the remote device and can apply control signals to the remote device.

It is known in the related art to provide remote units that can do little more than acquire and possibly reformat status signals from a device for transmission to a central control device. Similarly, fairly simple interface units can be provided for receiving signals from a central control device and for applying properly formated control signals to a remote device.

On the other extreme, it is known to provide an elaborate systems with dedicated communication lines and/or communication devices for controlling complex processes.

The device acquire status data from monitored remote devices or processes and can supply control signals to the remote devices for controlling the processes. Such systems are extremely costly and can be relatively inflexible.

In addition, the investment to provide such a complex system can limit the system to relatively few applications.

A need has therefore been felt for a remote interface unit that can communicate with a variety of process and control systems and can be expanded as the requirements for data signal acquisition or data signal distribution change. Not only is it desirable to have each interface unit easily expandable from a relatively simple unit to a unit having extensive independent decision capability, but it is desirable to be able to couple a plurality of remote interface units to a remote interface unit coupled to a data processing for added control and for immediate interaction at more than one remote sites.

It is therefore an object of the present invention to provide an improved remote interface unit.

The invention provides a remote interface unit for use with a host data processing unit comprising, a system bus; processing means coupled to said system bus for manipulating data on said system bus in accordance with a program; communication means coupled to said system bus for exchanging data signals with said host processor system; input signal means coupled to said system bus for receiving input signals; and output signal means coupled to said system bus for applying control signals to an output terminal.

The invention also provides a remote interface unit for coupling electronically a host data processing system and a device comprising; control means; first signal means coupled to said control means for receiving status signals from said device; communication means coupled to said control means for receiving signals from and transmitting signals to said host data processing system; said control means applying signals to said communication means determined by said status signals; and second signal means coupled to said control means applying control signals to said device; said control means applying signals to said second signal means determined by signals received by said communication means.

The invention further provides an expandable remote interface unit for electrically coupling a host data processing system and at least one device comprising; power means for receiving ac power and a dc power for supplying power to said remote interface unit; communication means adapted to receive signals directly from said host data processing system and to receive signals via a communication channel; signal means for transmitting and receiving signals from other remote interface units; processor means for controlling transfer of signals in said remote interface unit; memory means coupled to said processor means for providing a selected amount of temporary signal storage and for providing a selectable amount of read-only-memory storage for data signals; and connection means for coupling at least one circuit board to said remote interface unit, said circuit board including means to provide an electrical interface between said remote interface unit and said device, said connection means including apparatus for coupling to said device when no circuit board is coupled to said remote interface unit.

The invention still further provides a method of expanding the capabilities of a remote interface unit comprising the steps of; coupling at least one module circuit board to said remote interface unit; and exhanging read-only-memory units to provide a control program consistent with said capabilities of said remote interface unit.

The invention yet further provides a remote interface unit for coupling said data processing system to any of a plurality remote devices comprising; means for coupling to at least one remote device of wherein said coupling means can be adapted to any of a plurality of remote devices; means for processing input signals from at least one of said plurality of remote device, said processing means processing said input signals at least in part on the coupling means coupled to said one remote device, said processing means processing signals at least in part on a control program, said processing means processing said input signals in part on operation of said data processing system; and means for applying output signals to said one remote device determined by said processing means.

The invention will be described further, by way of example, with reference to the accompanying drawings, wherein: Fig. 1 is a block diagram of a system using the remote interface unit of the present invention; Fig. 2 is a block diagram of a remote interface unit according to the instant invention; Fig. 3 is a block diagram signal aquisition and distribution system using a plurality of coupled remote interface units; Fig. 4 is a schematic circuit diagram of apparatus for verifying an output signal logic state and for setting the output signal logic signal in event of malfunction; and Fig. 5 is a schematic circuit diagram of apparatus for detecting a loss of communication.

Referring to Figure 1, the system using the remote interface device of the instant invention is shown. Host data processing unit 5 is coupled to the remote interface unit 10 via communication line 4 and signal line 3. The remote interface unit 10 is coupled to a plurality of remote process devices 16 through 18.

Referring next to Figure 2, a block diagram of the remote interface unit is shown. power input terminal 251 is coupled to line filter 201. The line filter 201 is coupled through switch 202 to transformer 203. Transformer 203 and battery input terminal 252 are coupled to switching regulator 204. Switching regulator 204 provides power to a +5 volt terminal, a +12 volt terminal and a -12 volt terminal. Communication terminal 253 is coupled through modern 205 to RS232 driver unit 206. Communication terminal 254 is coupled to I loop drive unit 208. RS232 driver unit 206 and I loop driver unit 208 are coupled through uart unit 207 to the system bus 207.

Communication terminal 255 is coupled through RS232 driver unit 214 and uart unit 215 to system bus 230. Remote process unit terminals 257 through 260 are coupled to module &num;1 through module &num;n respectively. Module &num;1 through module &num;n are coupled to the system bus 230. Remote device terminal 256 is coupled to digital signal in unit 216. Remote device terminal 257 is coupled to digital signal in unit 216. Remote device terminal 257 is coupled to digital signal out unit 217.

Remote device terminal 258 is coupled to analog signal in unit 218. The analog signal in unit 218 includes multiplexer unit 218c, prorammable gain unit 218b and analog to digital converter 218c. Digital signal in unit 216, digital signal out unit 217 and analog signal in unit 218 are coupled to system bus 230.

RAM unit 210, timer unit 209, interrupt card unit 213, eprom unit 211, eeprom unit 212 and microprocessor unit 220.

Referring to Figure 3, the expansion of the system to include multiple remote interface units is shown. Remote interface unit 10 is coupled to remote interface 11 through re mote interface unit 13. A plurality of remote process devices, 17 through 19, are coupled to remote interface unit 11, while a plurality of remote process devices 12 through 14 are coupled to remote interface unit 13.

Referring now to Figure 4, a circuit for verifying at an output signal is correct is shown.

Bistable circuit unit 41 is coupled to a first input terminal of exclusive OR logic element 44. An output terminal exclusive OR logic element 44 is coupled to a first terminal of logic AND gate 45, while an output terminal of logic AND gate 45 is coupled to first terminal of exclusive OR logic element 46. The output terminal of exclusive OR logic element 46 is coupled through light emitting diode 48 and a resistive element to ground potential and is coupled through resistor 49 to amplifier 51.

The output terminal of amplifier 51 is coupled to an output terminal of the interface unit and through resistor 50 to bistable circuit 42. A bistable circuit 43 is coupled to a second input terminal of logic AND logic 45. Switch 47 has a positive voltage position and a ground position and is coupled to a second input terminal of exclusive OR logic gate 44 and to a second input terminal of exclusive OR logic gate 46.

Referring next to Figure 5, a circuit for determining if the communication to the host processor has been interrupted is shown. The communication with the host processing unit occurs through an electrooptic coupler 55.

The electro-optic coupler includes a light-emitting diode and a photo-detector diode and provides for the electrical isolation of the host data processing unit and the remote interface unit. The input signal from the electro-optic coupler is applied to counter/timer unit 56 and to a first signal inverting terminal of logic AND gate 59. The second signal inverting terminal of logic AND gate 59 is coupled to an output terminal of timer/counter unit 56. The output terminal of counter/timer unit 56 is also coupled to buffer circuit 58 and to a first inverting input terminal of logic AND gate 57. A second inverting input terminal of logic AND gate 57 is coupled to the system clock. An inverting signal output terminal of logic AND gate 57 is coupled to an input terminal of counter/timer unit 56.

Referring to Figure 2, the operation and features of the remote interface unit 10 will be described. Remote interface unit 10 terminal 253 receives signals from and sends signals to the host processing unit. Depending on the distance from the host processing unit 5, a modem 205 can be employed and is coupled to long distance communication channels.

Otherwise RS232 drive unit 206 can directly exchange information with the host processing unit. The output signals of RS232 driver are applied to uart (universal) asynchronic receiv e/transmit) unit 207 and to I loop driver unit 208. The I loop driver unit 208 is coupled to terminal 254, the terminal for communication with other remote interface units. The uart unit 207 converts incoming serially formated signals, and reformats the signals into a paras lel format and applies these signals to the system bus 230. The uart unit 207 also, receives signals from the system bus 230, changes the format of the signals from a parallel to a serial format, and applies the signals to the communications line 4 coupled to the host processing unit 5.

Communication with the remote interface unit can also be accomplished by means of terminal 255. Terminal 255 is coupled to RS232 driver unit. The RS232 driver unit is coupled through uart unit 215 to the system bus 230. The uart unit 215 serves the function of providing an interface between the serially formatted communication line and the parallel-formated system bus. The use of terminal 255 is to permit access to the remote interface unit by a local processing unit. This terminal or port is generally for use by a maintainence processor or other maintainence apparatus for exchanging signals with the remote interface unit for diagnostic or maintainence procedures.

Microprocessor 220 is coupled to the system bus 230 and performs the control functions and manipulative functions. The microprocessor 220 is an Intel 8088 16-bit processor. As will be discussed the remote interface unit have expanded capabilities. Therefore, the microprocessor must have sufficient power to accommodate the expansion of the system.

For some modes of operation, the Intel 8088 processor will have unused capabilities, but will be immediately expandable as required by modes having expanded capabilities. Supporting the microprocessor are an interrupt card unit 213, a timer unit 209, a ram (random access memory) unit 210, and eprom (erasable programmable read-only-memory) unit 211 and an eeprom (electrically erasable programmable read only memory) unit 212. The ram unit 210 provides a working memory for use as required by the microprocessor. The eprom unit 211 generally holds the operating system or control program. Typically this operating system will be related to the expected activity of the interface unit. In order to alter the operating system, the read-only-memory units can typically be replaced by another unit.The change of read-only-memory units is simply a matter of removing unit from the socket and placing another unit therein. In the preferred embodiment unused sockets are provided for additional eprom and eeprom units. The eeprom unit generally stores the application programs and can be altered externally to accom- modate more demanding activity by the remote interface unit. Typically, the ram unit 210 and the eprom unit are expandable to provide support for the microprocessor for expanded or for unexpanded activity by the remote interface unit. The interrupt card unit 213 serves the function of responding to requests for the microprocessor and for prioritizing the requests. The timer unit 209 provides the periodic signals required for the operation and synchronization of activity of the remote interface unit.

The power supply for the remote interface unit must be flexible enough to accommodate the uncertain situation with respect to location. Thus input terminal 251 can accommodate either 110 volt or 220 volt power with switch 202 providing the application of the correct input voltage to the transformer 203.

The transformer and terminal 251 are coupled to switching regulator 204. Terminal 252 is provided to receive 24 volt DC power and is provided in order that battery power can energise the remote interface unit in location where other power is unavailable. The output terminals of switching regulator 204 provides voltage of +5 volts dc, + 12 volts dc and - 12 volts dc are coupled to a power bus and to the system analog signal bus 231.

The system bus 230 is coupled to a digital in signal unit 216, a digital out signal unit 217 and an analog in signal unit 218. The analog signal in unit 218 can include a multiplex unit 218a, a programmable gain amplifier 218B and an analog-to-digital converter unit 218c.

The analog-to-digital converter unit also includes apparatus for applying digital signals to the system bus. With those components for the remote interface unit 10, a basic unit is described. The remote interface unit can apply digital control signals to remote devices via terminal 25, can receive status digital signals from the remote devices via terminal 258. Selected devices can be omitted from the basic unit in certain applications. For example, the presence of the programmable gain amplifier is necessary only for certain types of analog detection devices that produce low output signal levels. None-the-less, the basic remote interface device can provide the basic function of receiving status signals and transmitting the status signals to the host processor unit.The host processor unit can then determine what the appreciate response is, and apply the appropriate response via digital signal out unit to the remote device.

Because the serial communication apparatus, it will be clear that the host processing unit can be any of a multiplicity of available units.

It is contemplated that the remote interface unit 10 would be effective when used in conjunction with the personal computer data processing units. It is further contemplated that in the basic remote interface unit configuration, the decision programming for responding to the status signals will reside in the host processing unit. However, the memory capacity of the remote interface unit is such that a portion of the decision making process can be transferred to the remote interface unit and microprocessor 220, and the remote interface unit can assume a reporting mode.

The remote interface unit of the present invention was particularly designed to have an expandable capability. The present unit has the physical structure to couple to a plurality of module circuit boards, module &num;1 through module &num;n with associated terminals for providing generally the functions associated with terminals 256, 257 and 258. (The physical structure of the remote interface unit is described in copending U.S. Patent Application Number , entitled "Package For an Expandable Remote Interface Unit" and assigned to the assignee of the instant application), Any or all of the physical slots available for the module circuit boards can be filled. The module circuit boards are coupled electrically to the system bus 230. The presence of a module and the identification of the type of module are communicated to the microprocessor program via the system bus.This information provided to the microprocessor program determines the response of the microprocessor program to data placed on the system bus from the identified module circuit board.

The modules available can be of a multiplicity of types. The modules are circuit boards for providing an electronic interface between the remote device circuits and the circuitry of the remote interface unit. In addition, the modules can be coupled to the analog signal bus. The analog signal bus is coupled to analog signal in unit 218 for processing of the analog signals. The modules for use with the remote interface unit can be multiplexed, can have analog outputs (by means of digital to analog converters), can autorange the analog input signals, and can respond to pulse input signals. The modules can be surge protected aswell as have other protective features.

The remote interface unit system can be expanded in another dimension. A plurality of remote interface units can be coupled together via terminal 254 to the remote interface unit coupled to the host processing unit. The other remote interface units 11 through 13 are coupled together and receive all the signals from the host processor. The remote interface units return signals to the host processor via RS232 driver unit 206. Thus the remote interface unit can be further expanded by a plurality of coupled remote interface units.

The remote interface unit, because of the possibility of being in relatively inaccessible locations has a multiplicity of checking features.

For example, the power bus including the +5 volts dc, + 12 volts dc and - 12 volts dc lines are coupled, along with a commercially available reference voltage to multiplexer 218a. The analog voltage signals of the power bus can then be compared, via the microprocessor program to the reference voltage to ensure that the voltages are within predetermined limit. If the voltages are not within the predefined limits, the host processor receives an appropriate communication.

Referring to Figure 4, two other important features are provided for the output signals of the remote interface unit. The first function is that the actual output signals can be compared against the expected output signal state. And the second function is that in case of failure, the output signal wili~have a predefined value as a result of the failure. Illustrated in Figure 4 is a single output signal path. Similar apparatus would be provided for each signal path. The input signal is applied to the exclusive OR logic gate 41 from bistable circuit 41, and is transmitted to the output terminal of the amplifier 51. The output terminal of amplifier 51 is the output signal and is stored in bistable circuit 42 for normal operation.The signal in the bistable circuit 42 can be compared with the expected logic level to establish that the correct signal was applied to the output terminal. In case of circuit failure, the state of the output signal is determined by the position of the switch 47 when the signal indicating circuit failure is stored in bistable circuit 43 and applied to AND gate 45. Thus, potentially catastrophic control signals are prevented from occuring as a result of circuit failure by the instant circuit.

Referring to Figure 5, apparatus for informing the host processor of loss of communication is provided. Input signals are received by the electrooptic coupler from the host computer. These signals are applied to timer/connector 56. When the signals from the electro-optic coupler are present, the counter/ timer 56is continually reset. When the signals are no longer present, the counter/timer circuit begins timing based on signals from the system clock. If the signals from the electro- optic coupler resume during the time-out period, the counter/timer is reset. If, however, the counter/timer unit times out, a signal is stored in buffer circuit 58 and applied to line 3 (i.e.

in Figure 1). Because of the serious consequences of loss of communication with host processor, a separate line is provided to signal a loss of communication. A similar apparatus is available in the remote interface unit directly coupled to the host processor to determine if communication with other remote interface units have been interrupted. This occurence is stored by means of logic signals and communicated to the host processing unit.

It will be clear that, in view of the the available processing capability, and the flexibility provided by the ability to interchange and expand the amount of memory in eprom and eeprom units, the remote interface unit can be used as an independent control unit. Such a mode of operation obviates many of the advantages provided by the control of an oeration residing in a centralised host data processing system, but can be accomplished with proper programming in the read-only-memory units and is a further illustration of the flexibility of the present invention. Indeed, it will be clear that, with minor changes in the remote interface unit and with proper programming in the read-only-memories, the remote interface unit can act as master unit for at least one other remote interface unit. With an appropriate operating system in the read-only-memory, the 253 terminal or the 255 terminal can be used to provide access to additional memory units.

The above description is included to illustrate the operation of the preferred embodiment and is not meant to limit the scope of the invention. The scope of the invention is to be limited only by the following claims. From the above discussion many variations will be apparent to one skilled in the art that would yet be encompassed by the scope of the invention.

Claims

1. A remote interface unit for use with a host data processing unit comprising: a system bus; processing means coupled to said system bus for manipulating data on said system bus in accordance with a program; communication means coupled to said system bus for exchanging data signals with said host processor system; input signal means coupled to said system bus for receiving input signals; and output signal means coupled to said system bus for applying control signals to an output terminal.

2. A remote interface unit as claimed in claim 1, wherein said input signal means includes a terminal for receiving analog signals and means coupled to said system bus for converting said analog signals to related digital signals and applying said related digital signals to said bus.

3. A remote interface unit as claimed in claim 2, wherein power signals are applied to said analog to digital converting means for verifying that signals are in a pre-determined range.

4. A remote interface unit as claimed in claim 1, wherein said output signal means includes verification means for verifying that an output signal has an expected logic state, said verification means further including a switch for determining an output signal in case of failure.

5. A remote interface unit as claimed in claim 1, wherein operation of said remote interface unit can be altered or expanded by replacement of an appropriately processed read-only-memory.

6. A remote interface unit as claimed in claim 1, including means for identifying an interruption in communication between said host data processing system and said remote interface unit.

7. A remote interface unit for coupling electronically a host data processing system and a device comprising: control means, first signal means coupled to said control means for receiving status signals from said device; communication means coupled to said control means for receiving signals from and transmitting signals to said host data processing system, said control means applying signals to said communication means deterniiNed by said status signals; and second signal means coupled to said control means applying control signals to said device; said control means applying signals to said second signal means determined by signals received by said communication means.

8. A remote interface unit as claimed in claim 7, wherein said stauts signals can have a digital format and an analog format, said remote interface unit including an analog to digital converter.

9. A remote interface unit as claimed in claim 7, further including means for verification of said control signals.

10. A remote interface unit as claimed in claim 7, further including apparatus for determining when communication between said host data processing system and said remote interface unit is inoperative.

11. A remote interface unit as claimed in claim 10, further including a status line coupled between said host data processing system and said interface unit for signalling to said host processing system that communication therebetweenis inoperative.

12. An expandable remote interface unit for electrically coupling a host data processing system and as least one device comprising: power means for receiving ac power and a dc power for supplying power to said remote interface unit; communication means adapted to receive signals directly from said host data processing system and to receive signals via a communication channel; signal means for transmitting and receiving signals from other remote interface units; processor means for controlling transfer of signals in said remote interface unit; memory means coupled to said processor means for providing a selected amount of temporary signal storage and for providing a selectable amount of read-onlymemory storage for data signals; and connection means for coupling at least one circuit board to said remote interface unit, said circuit board including means to provide an electrical interface between said remote interface unit and said device, said connection means including appratus for coupling to said device when no circuit board is coupled to said remote interface unit.

13. An expandable remote interface unit as claimed in claim 12, further including means for automatically checking voltage levels of voltages supplyed by said power means.

14. An expandable remote interface unit as claimed in claim 12, further comprising maintenance means for coupling said remote inter face unit to a local signal generating means.

15. An expandable remote interface unit as claimed in claim 12, further including means for coupling analog signals from said connection means to said remote interface unit.

16. An expandable remote interface unit as claimed in claim 15 wherein said analog signal coupling means includes an analog to digital converter, a programmable gain amplifier and a multiplexer unit.

17. An expandable remote interface unit as claimed in claim 12, wherein operating characteristics of said remote interface unit are controlled by a program stored in a read-onlymemory unit.

18. A Method of expanding the capabilities of a remote interface unit comprising the steps of: coupling at least one module circuit board to said remote interface units; and exchanging read-only-memory units to provide a control program consistent with said capabilities of said remote interface unit.

19. A method as claimed in claim 18 further including the step of coupling at least one additional remote interface unit to said remote interface unit.

20. A method as claimed in claim 18, further including the step of processing a readonly-memory of said remote interface unit to provide a control program consistentwith said capabilities.

21. A method of providing an electrical interface between a data processing system and at least one device comprising the steps of: providing a remote interface unit with a circuit capable of interacting with said at least one device; receiving first signals by said remote interface unit from said at least one device; providing said remote interface unit with a control program to permit said remote interface unit to interact with said at least one device; processing said first signals in a manner determined by said remote interface unit; and applying second signals to said at least one device.

22. A method as claimed in claim 21, further including the steps of verufying that said second signals applied to said at least one device are the expected signals.

23. A method as claimed in claim 22 further including the step of applying settable second signals to said at least one device when a malfunction is detected in said remote interface unit.

24. A method as claimed in claim 21, including the step of coupling at least one additional remote interface unit to said one remote interface unit.

25. A remote interface unit for coupling said data processing system to any of a plurality remote devices comprising: means for coupling to at least one remote devices wherein said coupling means can be adapted to couple to any of a plurality of remote devices, means for processing input signals from at least one of said plurality of remote device, said processing means processing said input signals at least in part on the coupling means coupled to said one remote device, said processing means processing signals at least in part on a control program, said processing means processing said input signals in part on operation of said data processing system; and means for applying output signals to said one remote device determined by said processing means.

26. A remote interface unit as claimed in claim 25, further including means for coupling said remote interface unit to at least one additional remote interface unit.

27. A remote interface unit as claimed in claim 25, wherein said control program is stored in a readonly-memory, said read-onlymemory configuration determined by operational capabilities of said remote interface unit.

28. A remote interface unit as claimed in claim 25, further comprising means for verifying said output signals.

29. A remote interface unit as claimed in claim 25, further comprising means for applying selected output signals to said one remote device upon detection of a remote interface unit malfunction.

30. A remote interface unit as claimed in claim 25, further comprising means for determining when communication between said remote interface unit and said data processing system are interrupted.

31. A remote interface unit as claimed in claim 25, further comprising means for communication with a local data processing unit for maintenance and malfunction activity.

32. A remote interface unit as claimed in claim 25, further including means for responding to analog input signals.

33. A remote interface unit substantially as hereinbefore described with reference to the accompanying drawings.

34. An expandable remote interface unit substantially as hereinbefore described with reference to the accompanying drawings.

35. A method of expanding the capabilities of a remote interface unit substantially as hereinbefore described with reference to the accompanying drawings.