Abstract:
A selective call receiver allows reprogramming of the options stored within a code plug only after entry of a correct password. After a predetermined number of unsuccessful attempts to enter a correct password, the selective call receiver is user disabled such that the user may not reenable the selective call receiver without returning the receiver to the manufacturer or without replacing expensive components thereof.

Description:
FIELD OF THE INVENTION 
     This invention relates in general to electronic devices with reprogrammable memories, and in particular to selective call receivers with reprogrammable code plugs. 
     BACKGROUND OF THE INVENTION 
     The theft of electronic devices is on the rise because of the convenient size of the devices and the high monetary return a thief can receive for stolen devices. One such electronic device is a selective call receiver. Many electronic devices have a variety of options, some or all of which can be activated upon purchase. For individualization of a device, it is desirable that a user be able to alter some or all of the device&#39;s optional features. These options are typically stored in an electrical erasable, programmable read only memory (EEPROM), but can be stored in other programmable nonvolatile memory devices. Allowing the user the ability of reprogramming some or all of the options, however, also allows a thief to reprogram these options unless the electronic device is protected against unauthorized reprogramming. 
     Each selective call receiver has a unique selective call address that allows for the receiver to receive selective call messages so addressed. The selective call address is typically stored in an EEPROM called a code plug. Other selective call receiver options are customarily established by other information stored in the code plug. Regrettably, allowing code plug reprogrammability to the user also allows for possible reprogramming of the EEPROM unauthorized by the user. 
     Generally, stolen selective call receivers are useless unless the selective call address can be changed. If the selective call address remains unchanged, the new user of the selective call receiver could only receive messages intended for the previous owner. In various selective call receivers manufactured today, the frequency that the receiver operates on can be altered by reprogramming the code plug. Altering the frequency would allow the selective call receiver to operate within another selective call system making the purchase of the stolen selective call receiver more desirable. Also, the purchase of a stolen electronic device would be less desirable if the user could not take advantage of all of the options for which the device was designed. 
     Thus, what is needed is a method and apparatus for protected reprogrammability of an electronic device. 
     SUMMARY OF THE INVENTION 
     In carrying out the above and other objects of the invention in one form, there is provided an apparatus to allow authorized reprogramming of at least a portion of the options stored in an electronic device, such as a selective call receiver, and to user disable the electronic device if a predetermined password is not correctly entered within a predetermined number of attempts. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a block diagram of a selective call receiver according to the present invention. 
     FIG. 2 is a top front left perspective of a selective call receiver according to the present invention. 
     FIG. 3 is a bottom front right perspective of a selective call receiver according to the present invention. 
     FIG. 4 is a depiction of the preferred embodiment of the present invention. 
     FIG. 5 is a flowchart of the protected reprogramming operation of the preferred embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIG. 1, a selective call receiver comprises an antenna 10 for receiving signals coupled to a selective call receiver circuit 12 that demodulates the signals received. A microprocessor controller 14 is coupled to the receiver circuit 12 for processing the received signals. A memory 16 is coupled to the microprocessor controller 14 for storing those messages containing the address of the selective call receiver as determined by the microprocessor controller 14. A code plug 18 is preferably an electrical erasable, programmable read only memory (EEPROM) coupled to the microprocessor 14 for providing option information, such as the address and frequency of the selective call receiver, to the microprocessor 14. Also stored in the code plug 18 are configurations of various optional features which enhance the operation and/or performance of the selective call receiver, such as the length and types of various alerts and alarms, the type of code used by the selective call receiver (e.g., alphanumeric, numeric or voice) and various reminder chirps such as an unread message reminder chirp every half hour. 
     A serial communications interface 19 comprises a serial input/output data port that allows digital communication between a device outside the selective call receiver and the microprocessor 14. A display device 20 visually presents information and is controlled by the microprocessor controller 14. Alerts 22 provide alarms, such as audible and visual alerts, to inform the selective call receiver user of various events and is also controlled by the microprocessor controller 14. User controls 24 allow the user to command the microprocessor controller 14 to perform the selective call receiver operations such as selecting and reading messages and other selective call operations well known to those skilled in the art. The user controls 24 typically include control switches such as an ON/OFF control button, directional controls, and a message read control. A battery 26 is coupled to the receiver circuit 12, the microprocessor 14, the display 20 and the alerts 22 to provide power for the operation of the selective call receiver. For a more detailed description of the structure and operation of a selective call radio paging receiver of the type shown in FIG. 1, reference is made to U.S. Pat. No. 4,518,961, U.S. Pat. No. 4,649,538, and U.S. Pat. No. 4,755,816, all commonly assigned to the same assignee as the present invention, and the teachings of which are hereby incorporated by reference. 
     Referring next to FIG. 2, the selective call receiver comprises a housing 30 including openings 32a and 32b in a front plate 34 with user selectable control buttons 24a and 24b, and 24c, respectively, accessible therethrough. A visual alert 22a is also viewable through opening 32a. An audible alert 22b is mounted behind slotted opening 32c. The display device 22 is a liquid crystal display (LCD) viewable through another opening 36 in a top plate 38. The display 20 of the preferred embodiment is capable of displaying alphanumeric information. Each activation of the user selectable control buttons 24a and 24b select one of the messages stored in memory 16 (FIG. 1). By activating the user selectable control button 24c, the user can display the selected stored message on the display device 20. A clip 40 is mounted on a back plate 41 of housing 30 to allow the user to mount the selective call receiver on the user&#39;s clothing, such as a belt or a pocket. 
     Referring to FIG. 3, a right plate 42 of the selective call receiver has an ON/OFF power switch 44 mounted thereon. Other user selectable controls could be added to the selective call receiver but are not essential to the operation of the present invention. A bottom plate 46 of the selective call receiver has an opening 48 for inserting the battery 26 (FIG. 1). A battery cover 50 restrains the battery 26 within the selective call receiver. The serial communications interface 19 has three receptacles 52a, 52b, and 52c for receiving three conductive plugs thereby forming a digital data input/output port. 
     Referring next to FIG. 4, an interface unit 60 contains the three conductive plugs to allow the selective call receiver 10 to be physically and electrically coupled thereto. In the preferred embodiment, the interface unit 60 allows reprogramming of the code plug 18 (FIG. 1) via a program in the microprocessor 14 of the selective call receiver. Reprogramming of the code plug 18 is handled by a computer 62 via a computer data port 64, such as an RS232 data port. The computer 62 could be a personal computer and the interface unit 60 could additionally serve as a battery charger for charging the battery 26 (FIG. 1). 
     Referring to FIG. 5, the processing of the reprogramming routine of the computer 62 (FIG. 4) starts at step 70, where the selective call receiver is accessed by the computer 62 via the interface unit 60 and the serial communications interface 19 (FIG. 3). The computer 62 places the selective call receiver in a upload mode 72, whereby the computer 62 uploads the information stored in the code plug 18. A password is requested from the user 74. The password is received 76 from a keyboard of the computer 62. If the password data received is equivalent to the password information stored in the code plug 78, a lockout counter LOCKOUTCNT is initialized to zero 80. The code plug can then be read or reprogrammed 84. The password information in the code plug can be encrypted to prevent anyone tampering with the serial communications interface 19 from reading the password information. 
     If the received password data is not equivalent to the password information stored in the code plug 78, LOCKOUTCNT is incremented by one 90. If LOCKOUTCNT does not equal seven 92, the reprogramming routine requests another password from the user 74. If LOCKOUTCNT equals seven 92, the selective call receiver is user disabled 94 and no further attempts to enter a correct password by the user will be allowed. The selective call receiver can be user disabled in a variety of ways. In the preferred embodiment, the display 20 (FIG. 2) displays an alphanumeric message stored in nonvolatile memory every time that the display 20 is activated. The alphanumeric message is &#34;PAGER DISABLED&#34;. In addition, when the receiver is user disabled an audible alert 22b and/or a visual alert 22a could be activated either continuously or intermittently which has the added advantages of being annoying to the user who attempted unauthorized reprogramming and quickly discharging the battery 26 causing the receiver to have no operating power. 
     An alternate embodiment would allow for the receiver to be functionally disabled upon the entry of a first incorrect password but would allow subsequent entries of passwords up to the predetermined number of attempts. After a predetermined number of failed attempts to enter the correct password, no further attempts to enter a correct password would be allowed. A subsequently entered correct password would functionally reenable the selective call receiver. 
     Once user disabled, the receiver can only be reenabled by returning the selective call receiver to a manufacturer designated repair facility or by replacing the parts so disabled. In the preferred embodiment, purchase of the user disabled parts for replacement amounts to a price substantially equivalent to the purchase of a new selective call receiver, thereby making theft of the protected selective call receivers economically disadvantageous.