Automatic programming system for standardizing multiplex transmission systems

Abstract

An automatic programming system for standardizing multiplex transmission systems to accommodate additional inputs. The plurality of inputs to be transmitted are respectively addressed from a central control unit which provides a second concurrent corresponding address to an output unit associated with the addressed input. The output unit is responsive to the second address to provide an enable signal to the control unit. Similarly, the control unit is responsive to the enable signal to process the corresponding input addressed into a desired output format and transmit the same to the corresponding output unit. If an address not associated with an input is generated by the control unit there will be no corresponding output unit to enable processing within the control unit, hence, the address will be ignored. Accordingly, the control unit can be designed to generate a number of addresses in excess of the number of inputs to accommodate expansion of the system by the incorporation of additional inputs and output units. The additional addresses, and any corresponding fault conditions activated, will thus be ignored until expansion of the system is desired. A specific application to nuclear reactor position indication is described which enables a standardized design to be incorporated regardless of the size of the reactor employed (i.e., the number of rods monitored).

Description

CROSS REFERENCE TO RELATED APPLICATIONS

The present invention is related to the inventions covered by copending U.S. Patent applications: (W. E. Case 43,906) Ser. No. 320,776 entitled "Position Indication System" by F. T. Thompson, Frederick J. Young and D. J. Boomgaard; and (W. E. Case 44,067) Ser. No. 320,792, entitled "Digital Multiplexed Position Indication and Transmission System" by J. A. Neuner, F. T. Thompson and L. Vercellotti. All of the aforementioned U.S. patent applications are assigned to the assignee of the present invention and are filed concurrently herewith.

BACKGROUND OF THE INVENTION

This invention pertains in general to multiplex transmission systems and more particularly to a standardized design for such systems to enable the accession and transmission of additional inputs.

In many electrical systems requiring the transmission of a multiplicity of inputs the well known technique of multiplexing is incorporated to reduce the number of field wires required to transmit the various signals and increase the overall efficiency of the system. The accommodation of additional inputs usually requires a total redesign of the system. A standardized design, with its associative cost savings, is not presently available due to the variety of inputs necessitated by the various applications.

An exemplary system requiring such a multiplexing set up is the digital multiplexed rod position indication system for nuclear reactors described in copending application Ser. No. 320,792, (W. E. Case 44,067) entitled "Digital Multiplexed Position Indication and Transmission System" cited above. As in most large systems of this nature, standardization, although desirable, is difficult to implement, since both the total number of control rods and their organization into banks usually varies from one reactor plant to another. In previous systems, the addition of each control rod entailed changes in the field and intrasystem wiring as well as in the control unit with considerable engineering cost added for each plant. In the cited Digital Rod Position Indication System, all the information is transmitted from the containment to the control room and from the control room to a computer using a simple time division multiplexing technique, therefore, external field wiring is unaffected by different core and/or plant configurations. However, even if the maximum possible number of rods is known, the intrasystem wiring cannot be standardized using conventional techniques since the number of rods actually existing and their organization into banks varies from plant to plant. The solution to the standardization problem is made more difficult by the functional requirement (for safety reasons) that the removal of any rod position encoding unit, which is used to encode the multiplexed signal, must result in the appearance of an error code during the address period assigned to the corresponding control rod. Error codes are detected by a single circuit monitoring all information still in a serially multiplexed form. If an error code is detected for each of two redundant encoder units, assigned to a given control rod, an urgent alarm is annunciated and the system is forced to indicate that one or more rods are at their bottom position. This condition would also unfortunately occur as a result of a standardized wiring scheme if both encoder units were missing because the corresponding rod was not used in a given plant unless a provision was made to account for the unused rod location. To overcome this problem it is necessary for the central unit to know which control rods exist and which do not, so that it can ignore alarms generated by non-existing rods. This can be accomplished with a unique set of backwiring or a unique programmed read only memory to customize the central control unit for each reactor plant. The obvious disadvantage is that the system would not be completely standardized for each plant and a considerable amount of additional engineering cost would be required. Furthermore, to build this flexibility into the control unit would increase its complexity making it more difficult to test and trouble shoot.

Thus, the availability of a technique that allows the intra-system wiring and printed circuit modules of the rod position indication system to be totally and unconditionally standardized would be extremely desirable and very effective in reducing engineering costs. Modules should be provided on a per-rod basis only, so that modules associated with non-existing rods can be eliminated while maintaining the intra-wiring capability of a full system. The error codes generated by the absence of unnecessary units should be automatically ignored by the central control unit without the need for specialized programming of any kind, while the error code generated by removing a legitimate encoder unit should always be recognized and indicated.

SUMMARY OF THE INVENTION

Briefly, this invention provides an automatic programming system for standardizing multiplexed transmission systems to accommodate a varying number of inputs. The plurality of inputs to be transmitted are respectively addressed from a central control unit which provides a second concurrent corresponding address to an output unit associated with the input addressed. The output unit is responsive to the second address to provide an enable signal to the control unit. The enable signal activates the control unit to process the corresponding input addressed into a desired output format and transmit the same to the corresponding output unit. Addresses generated by the control unit which have no corresponding input are ignored inasmuch as no corresponding enable signal exists to activate the control processing circuitry. Accordingly, the control unit can be designed to generate a number of addresses in excess of the number of inputs and output units to accommodate expansion of the system by the incorporation of additional input and output units responsive to corresponding ones of the excess of addresses.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention, reference may be had to the preferred embodiment, exemplary of the invention, shown in the accompanying drawings, in which:

FIG. 1 is a block diagram of a position indication system incorporating the concepts of this invention; and

FIG. 2 is a block diagram illustrative of the intercourse of signals employed in the embodiment illustrated in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In most multiplexing applications the advantages obtained can be enhanced by a standardized design which can be incorporated to accommodate a varying of number of inputs. This invention provides such a standardized design which can be incorporated into most multiplexing applications. While the system contemplated by this invention will be described in an application to control rod position indication for nuclear reactors, it should be understood that this invention has analogous applicability in most multiplexing systems.

To provide reliable and accurate nuclear control rod position information, even under single failure conditions, for each control rod, the detector coils and the associated containment electronics employed within the position indication system contemplated by this invention and respectively described by reference characters 10 and 20 in FIGS. 1 and 2 (more fully described in copending application Ser. No. 320,792, W. E. Case 44,067 cited above) are divided into two separate identical groups A and B. Each group is capable of providing redundant information on the true position of each control rod with one-half the overall resolution of the system. The two sets of digital data are transmitted through independent time division multiplexed channels to the reactor control room where independent error checking is performed. The two sets of verified data are sent to a central control unit 30 and combined to determine the true position of the control rod with full resolution.

If a failure occurs in either group, it will be automatically detected resulting in the rejection of the corresponding data so that the true rod position, determined by the remaining group, will still be displayed with reduced resolution.

Rod position information is available through independent and separate outputs including a location real time display using light emitting diodes for the reactor operator, and a plant computer which operates as a data logger. A block diagram of the overall rod position indication system with its individual component systems is illustrated in FIG. 1. Redundancy is implemented within the detectors 10, containment electronics 20 and display area 40 as pictorially illustrated by groups A and B, respectively identifying the separate signal trains. The operation of each of the individual blocks identified by legends can better be understood by reference to the explanation provided in copending application Ser. No. 320,792, W. E. Case 44,067 cited above.

Standardization is implemented in accordance with this invention by employing a logic signal ("GO" signal) which is returned to the central control unit 30 by each display unit 40 when addressed, as illustrated in the block diagram provided in FIG. 2. Since one display unit is associated with two encoder units corresponding to a given rod location and is addressed at the same time as the encoder units whenever new data is requested for that rod, the return of a "GO" or "enable" signal from a display unit will acknowledge not only the presence of that display unit but also the existence of a rod to be monitored in the corresponding location and therefore will verify the validity of any existing error code generated. All the "GO" signal terminals on the various display units are OR-wired together in a single bus configuration. Any display unit, when plugged into the system, will activate the "GO" signal when addressed by the control unit and will enable acknowledgement of any possible corresponding error codes which may be generated.

Removal of a display unit can easily be recognized since the corresponding visual display will obviously be missing, while the correct information will still be available for the computer. The computer can be programmed to know which rods are used and which are not so that it can properly accept or reject incoming error codes.

A completely standardized intra-system wiring configuration primarily employing bus wiring can then be established to accommodate the largest possible number of control rods. The only affect of a missing encoder unit is the generation of a error code "11111" during the corresponding address period as described in the operational description of application Ser. No. 320,792, W. E. Case 44,067. The standard central control unit is hard wired to ignore the resulting error code, as explained in the aforecited application with accompanying figures, unless a "GO" signal is activated at the same time by the display units. This signal results from the OR-busing of the individual "GO" signals generated by each display unit when addressed by the control unit. Removal of a display unit will cause the "GO" output to float and assume a "0" logical state in the corresponding address period, (the same as if no display card were addressed) with the result that the central control unit will ignore any error signal generated during that address period.

In the system described in the aforecited application, if a rod location is not employed, the associated encoder unit positions will be vacant causing an error code to appear in the assigned time period. However, the corresponding display unit will also be missing, causing the GO signal to assume the logical 0 state and the control unit to ignore the error code.

This invention permits the implementation of a fully standardized intra-system wiring scheme that can be employed for any reactor plant configuration. The resulting interconnection layout is particularly appealing because it extensively uses busing of corresponding terminal pins and minimizes specialized point-to-point connections. An exemplary wiring layout and circuit schematic for each of the units illustrated in block form, together with an operational description thereof, is provided in the aforecited copending application.

The main advantage provided by this invention is that it permits any control rod position indication system and most other multiplexing applications to be implemented by means of a completely standardized wiring scheme employing a minimum number of identical printed circuit modules. This results in a larger volume of identical intra-system wiring packages and makes possible the use of cost saving manufacturing techniques such as automated point-to-point wiring or printed circuit backwiring; both made even simpler by the predominance of bus oriented interconnection patterns. Thus, the reoccurring engineering time and engineering costs required for each new reactor plant and multiplexing application by previous conventional approaches are minimized. In addition, by entirely avoiding hard-wired customization, both training for and the execution of maintenance procedures are greatly simplified.

Claims

We claim as our invention:

1. An automatic programming system for standardizing multiplexed transmission systems comprising:

a plurality of input units respectively providing a corresponding data signal output;

a central control unit electrically coupled to the output of each of said input units and operable to generate, sequence and transmit a plurality of first and second corresponding addresses; and

a plurality of output units, each output unit corresponding to at least one input unit and responsive to a corresponding one of said second addresses to communicate a corresponding enable signal to said control unit, each input unit receiving a corresponding first address and responsive thereto to communicate said data signal to said control unit, said control unit being responsive to said enable signal corresponding to said input unit addressed, to process said data signal and communicate an output signal representative thereof to said corresponding output unit.

2. The multiplexed programming system of claim 1 wherein said plurality of first and second corresponding addresses is greater in number than said plurality of input units forming an excess of said first and second addresses and said multiplex system is expanded by assigning one of said corresponding excess of said first and second addresses to each added input unit and output unit respectively, constituting the multiplexed systems expansion.

3. The multiplexed programming system of claim 1 wherein said enable signals from said plurality of output units are OR-wired together in a single bus configuration to said central control unit.

4. A digital position indication system for displaying the relative position of a movable element with respect to fixed known coordinates comprising:

a sensory system responsive to the element's position to provide discrete electrical outputs indicative thereof;

an encoder system operable upon said discrete outputs to provide a digital coded output representation of the element's position;

an interface system operable upon said digital coded outputs to respectively transmit said digital coded outputs upon a first corresponding command address signal;

a central control unit for generating, sequencing and transmitting said first command address to said interface system and a second corresponding command address, said interface system being responsive to said first address to effect transmission of a corresponding one of said digital coded outputs to said control system for processing into a decoded display signal; and

a plurality of display units, each display unit corresponding to at least one of said digital coded outputs and responsive to a corresponding one of said second addresses to communicate a corresponding enable signal to said control unit, said control unit being responsive to said enable signal corresponding to said digital coded output addressed by said corresponding first address to process said digital coded output and communicate a display output signal representative thereof to said corresponding display unit.

5. The digital position indication system of claim 4 for displaying the relative position of a plurality of movable elements with respect to fixed known coordinates wherein:

said sensory system includes a plurality of sensors corresponding to the plurality of elements, said sensors being responsive to the respective element's position to provide corresponding discrete electrical outputs indicative thereof;

said encoder system includes a plurality of encoder units corresponding to said plurality of sensors and operable upon the corresponding respective discrete outputs to provide a corresponding digital coded output representation of the corresponding element's position; and

said plurality of first and second corresponding addresses is greater in number than said plurality of encoder units so as to form an excess of said first and second addresses without corresponding digital coded outputs so that the position indication system can be expanded to monitor the position of additional elements by including a corresponding sensor, encoder unit and display unit for each additional element and assigning one of said corresponding excess of first and second addresses to each additional corresponding digital output and display unit, respectively.