Circuit breaker trip unit which automatically adapts to operated with a particular display module
CROSS-REFERENCE TO RELATED APPLICATION 
     This is a continuation of Ser. No. 08/198,683 filed Feb. 18, 1994 now abandoned, which is in turn a continuation of application Ser. No. 07/847,709, filed on Mar. 6, 1992 now abandoned. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a circuit breaker trip unit having a display. More specifically, the present invention relates to a trip unit which is coupleable to one of a plurality of different displays, where the trip unit is configured to automatically recognize the type of display to which it is coupled and apply signals to the display unit which are compatible with the display unit. 
     BACKGROUND OF THE INVENTION 
     In general, display units for circuit breaker trip units are known. Referring to U.S. Pat. No. 4,870,531 issued to Robert J. Danek, there is shown a circuit interrupter having a display for viewing circuit interrupter settings. The display removably connects to the electronic trip unit of the interrupter, and displays interrupter values and settings when in operation. When the display unit is not in place, a security cover 20 may be positioned within a recess which is adapted to accept the display. 
     U.S. Pat. No. 4,751,605, issued to Mertz et al., also discloses a trip device for a circuit interrupter having a display unit. The display unit is portable and is coupleable to the trip device to display various circuit interrupter values. The display unit includes an alphanumeric display, a microprocessor, memory, and an apparatus associable with complementary apparatus in the trip device to transfer the contents of memory areas in the trip device to the memory of the display device. The content of the memory is selectively displayed by the reader. 
     While various display unit configurations are available for circuit interrupters (breakers), it would be useful and desirable to provide a trip unit useable with a plurality of different display units, where each display unit is configured to display a range of values for a given variable monitored by the trip unit e.g. current, temperature, energy, power, etc. Accordingly, depending upon the application for a circuit breaker, only a display unit configured to display the variables which are needed for the application is provided. 
     SUMMARY OF THE INVENTION 
     The present invention provides a circuit breaker trip unit. The trip unit includes a first connector, a processor, a data bus coupled between the connector and the processor, and a display module. The display module includes a memory which stores configuration data, and a second connector coupled to the memory and the first connector. The processor reads the configuration data and controls the data transfer between the processor and module based upon the configuration data. 
     The present invention further provides a system for adapting the operation of a trip unit to a particular display module. The trip unit includes a processor, and a first connector coupled to the processor. The system provides at least two display module types, where a first display module includes a first memory which stores a first configuration data coupled to a second connector. A second display module includes a second memory which stores a second configuration data coupled to a third connector. When the first and second connectors are connected, the processor reads the first memory, and applies first display data to the first display module in response to the value of the first configuration data. When the first and third connectors are connected, the processor reads the second memory and applies second display data to the second display module in response to the value of the second configuration data. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded, schematic view of a circuit breaker contact and operating mechanism unit, a trip unit and a display unit; 
     FIG. 2 is a side, schematic view of the circuit breaker contact and operating mechanism, trip unit and display unit when coupled; 
     FIG. 3 is the circuit diagram for the display unit; and 
     FIG. 4 is the circuit diagram for the circuitry of the trip unit which interfaces with the display unit. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIGS. 1 and 2, a circuit breaker 10 includes a circuit breaker contact and operating mechanism 12, an electronic trip unit 14, and a removable and interchangeable display unit 16. Mechanism 12 may be a conventional mechanism including the operating linkages and energy storing devices for opening the contacts of circuit breaker 10. Additionally, mechanism 12 includes monitoring devices, such as current transformers and temperature sensors, which produce status signals representative of the current flows and various temperatures in circuit breaker 10. The monitoring devices are electrically coupled to a connector 18 of mechanism 12 such that the status signals for the monitoring devices are applied to connector 18. Additionally, mechanism 12 includes tripping devices which are coupled to connector 18 and cause mechanism 12 to open the circuit breaker contacts in response to the application of control signals at connector 18. 
     Electronic trip unit 14 is of the type including a programmed micro-controller 20 (processor) which has circuitry coupled to a connector 22 for monitoring the status signals applied to connector 18. The circuitry includes devices for performing conditioning functions such as analog-to-digital conversion and filtering so that processor 20 may properly monitor and analyze the status signals at connector 18. Unit 14 also includes a plurality of limit set inputs such as potentiometers 24. Potentiometers 24 allow variables such as long time delay, short time pick-up, short time delay, instantaneous pickup, ground fault pickup and ground fault delay to be adjusted. Based upon the values of the status signals and the settings at potentiometers 24, processor 20 applies the appropriate control signals and display signals to connectors 18 and 26, respectively. Connector 26 is connected to processor 20 by a data bus 34 and appropriate interface circuitry. 
     Connector 22 is mechanically and electrically connected to connector 18 when circuit breaker 10 is assembled. Of course, unit 14 could be appropriately wired to mechanism 12 without the use of connectors 18 and 26. 
     Display unit (module) 16 may have a plurality of configurations, and, generally, includes a multi-digit display 28, a multi-position switch 30, a connector 32, and a memory 36 for storing configuration data (address). Memory 36 may take the form of dip switches, a set of jumpers (presently preferred embodiment), PROM or other types of ROM. Display 28, switch 30 and memory 36 are coupled to connector 32 such that data may be transferred between unit 14 and unit 16 along data bus 34 when units 14 and 16 are mechanically connected, and connectors 26 and 32 are mechanically and electrically connected. 
     When unit 14 is operating, and coupled to unit 16, unit 14 reads the data in memory 36 (e.g. 4 bits, one associated with each of 4 jumpers 46, 48, 50 and 52) to determine the configuration of unit 16. Three (3) of the 4 bits of data are available for configuration data, thus, unit 14 can automatically recognize 8 different unit 16 configurations. Upon recognizing the unit 16 configuration, processor 20 operates under the control of the portion of the program stored in unit 14 associated with the particular configuration. For example, one unit 16 may be programmed to display amperage, where each switch 30 setting is associated with different amperage readings while other units may be configured to display a circuit breaker variable such as temperature, power or energy use. Furthermore, display unit 16 may be configured such that trip unit 14 reads switch 30 to acquire control or limit values such as alarm limits. By way of example, switch 30 may include 10 settings thus allowing the display of 10 different characteristics (values) of a given variable, control value or limit value. 
     Referring more specifically to the characteristics (values) associated with the ten switch positions of switch 30, when switch 30 is associated with a display unit 16 configured to display amperage, switch 30 settings may include: 
     Present demand, which provides data for processor 20 so that the average amperage load for the last 15 minute period is displayed; 
     Maximum demand, which provides data for processor 20 so that the maximum amperage load since power was applied to the circuit breaker is displayed; 
     Phase A current, which provides data for processor 20 so that the amperage load for phase A is displayed; 
     Phase B current, which provides data for processor 20 so that the amperage load for phase A is displayed; 
     Phase C current, which provides data for processor 20 so that the amperage load for phase C is displayed; 
     60% load monitor set point, which provides data for processor 20 so that the maximum phase current is displayed and flashed when the current exceeds 60% of the rated value; 
     70% load monitor set point, which provides data for processor 20 so that the maximum phase current is displayed and flashed when the current exceeds 70% of the rated value; 
     80% load monitor set point, which provides data for processor 20 so that the maximum phase current is displayed and flashed when the current exceeds 80% of the rated value; 
     90% load monitor set point, which provides data for processor 20 so that the maximum phase current is displayed and flashed when the current exceeds 90% of the rated value; and 100% load monitor set point, which provides data for processor 20 so that the maximum phase current is displayed and flashed when the current exceeds 100% of the rated value. 
     Subsequent to determining the configuration of a particular display unit 16, processor 20 reads the status of switch 30, and transmits display data to unit 16 over data bus 34, where the display data is representative of the characteristic selected at switch 30 and the particular configuration of unit 16 (i.e. the data in memory 36). Thus, if processor 20 reads memory 36 and determines that unit 16 is an amperage display unit, reads switch 30 and determines that the RMS current for phase A is to be displayed, processor 20 will access the appropriate programming and apply the appropriate display data to display 28 via data bus 34 to display the RMS current value for phase A in digital form (alphanumeric) on display 28. 
     Referring to FIG. 3, FIG. 3 illustrates the circuitry for display unit 16. Unit 16 includes switch 30 coupled to the four low order bits (lines) of data bus 34 by buffers 38, 40, 42 and 44. As discussed above, the presently preferred embodiment of memory 36 may include a set for four jumpers 46, 48, 50 and 52. Jumpers 46, 48, 50 and 52 are coupled to the four high order bits (lines) of data bus 34 by buffers 54, 56, 58 and 60, respectively. When address select line 62 of bus 34 (address 2A00 hex) goes low, switch 30 and memory 36 settings are read by processor 20 over data bus 34. 
     Display unit 16 also includes four seven segment LED&#39;s 64, 66, 68 and 70, and a display driver 72. (By way of modification, displays 64, 66, 68 and 70, and display driver 72 may be replaced by a single chip unit depending upon the application.) Data bus 80 couples display driver 72 to displays 64, 66, 68 and 70. Display driver 72 is coupled to data bus 34 and is controlled by address select lines 74 (address 2800 hex) and 76 (address 2900 hex). A data line 78 is the processor 20 read/write line. When processor 20 writes to address 2800, lines 74 and 78 go low. Address 2800 is used to send data to display driver 72. When processor 20 writes to address 2900, lines 76 and 78 go low. This address is used to send control commands to display driver 72. 
     When display unit 16 is plugged into trip unit 14, data line J8-19, J8-17, J8-15, J8-13, J8-2, J8-4, J8-6, and J8-8 (D0-D7) connect unit 16 to trip unit 14 via data lines J2-19, J2-17, J2-15, J2-13, J2-2, J2-4, J2-6, and J2-8 (D0-D7), respectively. Also, address select lines 74, 76, 62, and 78 are connected to trip unit 14 via address select lines J2-16, J2-14, J2-12 and the read/write line J2-10, respectively. 
     Referring to FIG. 4, the trip unit circuitry includes a processor 20 (Motorola 68HC11F1) coupled to data bus 34, and buffer 82 also coupled to data bus 34. Buffer 82 acts as an isolation buffer between display unit 16 and trip unit 14 for data lines E0-D7. The circuitry of unit 14 also includes an isolation buffer 84 coupled to a decoder 86 which in turn is coupled to an address bus 88 coupled to processor 20. Buffer 84 acts as an isolation buffer between display unit 16 and trip unit 14 address select and read/write lines. 
     In addition to processor 20, buffer 82, buffer 84 and decoder 86, unit 14 includes an EPROM 90 coupled to data bus 34 and address bus 88. The programming for processor 28, which controls the transfer of data between display unit 16 and trip unit 14, is stored in the memory of processor 20 and EPROM 90 (the source code for this programming is included in Appendix A). 
     In operation, when processor 20 reads address 200 (address line 62), data bit 7 (data line J8-8) is tested for a high state. If it tests high, then processor 20 assumes that trip unit 14 and display module 16 are connected via connectors 26 and 32. In response, a portion of the display module control code (Appendix A) is activated. Subsequently, the type of display unit 16 is determined by decoding data lines J8-8, J8-6, J8-4 and J8-2. After the type of display unit 16 is determined, the position of switch 30 is determined by decoding data lines J8-13, J8-15, J8-17, and J8-19. Based upon this data, processor 20 then selects the function from the display module software (code) which is to be activated such that data is applied to display 28 to provide proper alphanumeric information at the display. When the values displayed at display 28 are to be flashed due to a maximum phase current exceeding a set point, as discussed above, processor 20 sets the line connected to J2-14 (connected to J8-14 of unit 16) of unit 14 high to signal that a load set point has been exceeded, and provide a flash signal to AND gates 92, 94 and 96. The flash signal causes the gates to control display driver 72 such that display 28 flashes. 
     It will be understood that the above description is of the preferred exemplary embodiment of the invention, and that the invention is not limited to the specific form shown. For example, various components of the above-described trip unit and display unit may be modified to combine various discreet components into single multi-function components. Furthermore, it is contemplated that portions of the software may be replaced with appropriately configured hardware, and, alternatively, depending upon the microprocessor or controller used as processor 20, the software may be modified such that hardware in the circuits may be eliminated. Various other substitutions, modifications, changes and omissions may be made in the design and arrangement of the elements without departing from the spirit of the invention, as expressed in the appended claims. ##SPC1##