ELECTRONIC LOCK SYSTEM

Abstract: An electronic lock system includes a key (20) which contains a precision resistor (22), a receiver (28) for receiving the key (20), an analog-to-digital converter (46) coupled to the receiver (28) for measuring the resistance of the precision resistor (22) of the key (20), circuitry (50, 56, 58) for controlling the analog-to-digital converter (46), decoding logic (82) for receiving data from the analog-to-digital converter (46) and decoding the data to provide information with respect to the type of key (20) applied to the receiver (28), and circuitry (64) for controlling the decoding logic. Two system embodiments are disclosed, one of which employs separate components, and the other of which employs a microcontroller (120) combining several functions.

Description: ELECTRONIC LOCK SYSTEM Technical Field This invention relates to electronic lock system of the kind including key receiving means adapted to receive a key which includes resistor means. The invention has a particular application where the electronic lock system is utilized in a point-of-sale or point-of-service terminal or in a financial terminal, such as a teller machine. Background Art An electronic lock system of the kind specified is known from U.S. Patent No. 3,673,467. In the known system a key having two resistors embodied therein is utilized in conjunction with a key receiving means which is connected to a pair of bridge circuits. When the bridge circuits are both balanced, an output control signal is provided. Disclosure of the Invention It is an object of the present invention to provide an electronic lock system of the kind specified, which is of inexpensive construction and which has versatile operating capabilities. Therefore, according to the present invention, there is provided an electronic lock system of the kind specified, characterized by measuring means- coupled to said key receiving means and including analog-to-digital conversion means adapted to provide a digital representation of the resistance of said resistor means; control means adapted to cause said analog-to-digital conversion means to provide said digital representation at a desired time; and translation means coupled to said analog-to-digital conversion means and adapted to translate said digital representation into output control signals. It will be appreciated that an electronic lock system according to the invention has the capability of a low-cost implementation and high reliability in operation. Furthermore, the system has the additional advantages of being adapted to provide unique keying for particular establishments or for particular classes of persons or individuals who use the system. Brief Description of the Drawings Two embodiments of the invention will now be described by way of example, with reference to the accompanying drawings, in whichs Fig. 1 is a block diagram of one embodiment of an electronic lock system according to the present invention. Figs. 2 and 3 are diagrams of two alternative arrangements which may be used for the combinational control of Fig. 1. Figs. 4A and 4B, taken together, constitute a diagram of the microprocessor control logic of Fig. 1. Fig. 5 is a block diagram of a second embodiment of an electronic lock system according to the present invention. Fig. 6 is a block diagram of a microcontroller which can be employed in the system of Fig. 5. Fig. 7 is a perspective view of a key which may be employed in the present invention. Fig. 8 is an elevation view of the key of Fig. 7. Fig. 9 is a plan view of the key of Fig. 7. Best Mode for Carrying Out the Invention Referring now to the embodiment of the invention shown in the diagram of Fig. 1, a key assembly 20 comprises a precision resistor 22 embodied in a case 24. A precision resistor may be defined as a resistor which has a tighter tolerance to nominal value than does a standard resistor. A resistor having a one per cent or tighter tolerance to nominal value and a temperature tolerance generally less than or equal to 200 parts per million per degree Centigrade is generally considered in the industry to be a precision resistor. The range of the resistors for the keys in the present invention has been determined to fall into the resistance range between 1,000 ohms and 750,000 ohms. The key assembly may have the external appearance shown in Figs. 7, 8 and 9, for example, though different external configurations could be selected, if desired. One example of a structure which can be utilized as the key assembly 20 is a Switchcraft miniature telephone plug, having a plastics material handle, manufactured by Switchcraft, Inc., Chicago, Illinois. The key assembly is used to provide locking and unlocking security for a device such as a point of sale terminal by operatively engaging it with a lock assembly, such as the electronic lock assembly shown in Fig. 1, and generally designated 26. Specifically, the key assembly 20 may engage a jack assembly or receptacle 28, for which a Switchcraft PC mount telephone jack may be employed. The jack assembly 28 is connected on one side through a precision resistor 30, the specific resistance value of which will be dependent upon the value of the key resistor 22, and a conductor 32 to a circuit node 34, and is connected on a second side by a conductor 36 to a node 38. The node 34 is connected to a +12-volt precision source of potential 40, while the node 38 is connected to analog ground 42. A precision potential reference source may be defined as a source which will hold a voltage to one per cent of nominal value, and which will hold that voltage over an extended temperature range. The temperature coefficient for a precision voltage reference is generally defined to be less than 50 parts per million per degree Centigrade. Connected between the nodes 34 and 38 is a precision reference zener diode 44, which may be of type LT1029ACZ, manufactured by Linear Technology Corp., Milpitas, California. The nodes 34 and 38 are also connected, respectively, to precision reference voltage (Vref) and analog ground inputs of a 10-bit analog-to-digital converter 46, which may be of type ADC1025, manufactured by National Semiconductor Corp., Santa Clara, California, thereby limiting the maximum potential across the resistor 22 to 6 volts. It will be seen that the circuit just described provides a means of measuring the resistance of the precision resistor 22 in the key assembly 20 by utilizing the analog-to-digital converter 46 to provide a digital value representative of the potential difference between inputs of said converter 46 which are coupled to the nodes 34 and 38. Control of operation of the analog-to- digital converter 46 is provided by a microprocessor 50, which may be of type 8085, manufactured by Intel Corp., Santa Clara, California, and which customarily will be included in the system circuitry of the point of sale terminal with which the electronic lock assembly 26 is associated. The microprocessor 50 provides an address for accessing the analog-to-digital converter 46 on an address bus 52. The address is latched in an address latch 54, which may be of a type manufactured by Texas Instruments, Dallas, Texas. The output of latch 54 is applied to an AND OR logic circuit 56, which may be of a type manufactured by Texas Instruments. The microprocessor 50 also provides a plurality of signals SYS CLK, RD/, WR/, IO-M/, SO, SI, ALE, RESET/ and HLDA to various inputs of the microprocessor control logic circuit 58, shown in block form in Fig. 1 and in greater detail in Figs. 4A and 4B. The signal SYS CLK is a system clock signal? the signal RD/ is a read signal; the signal WR/ is a write signal; the signal IO-M is an input signal from the microprocessor indicating that the next processor signal to be executed will be an I/O or memory instruction; the status signal S1-S0 indicates that the next machine cycle will be a read, write, instruction fetch or a halt; the signal ALE is a latch enable signal; the signal RESET/ is an active low reset signal; and the signal HLDA indicates that the microprocessor has acknowledged a hold condition from another device which shares the processor system bus. These signals are conventional outputs from the microprocessor 50 and will not be described in greater detail. The microprocessor control logic circuit 58 receives these signals and provides a number of output signals, of which the outputs BIOR/ and BIOW/, relating to reading and writing, are the only ones which are of specific interest in the present invention. The circuit 58 is embodied in the illustrated embodiment in a memory control chip, which may be of type 006-1007971, manufactured by NCR Corporation, Dayton, Ohio, but could also be implemented in the form of individual elements, and will be briefly described below in that form. The various signals referred to above appear on terminations 200 on the left side of Fig. 4A. Each of said terminations 200 is coupled through a connecting pad 202 to an input buffer 204. The output of the input buffer 204 associated with the SYS CLK signal is applied to a clock drive 206 which provides both clock and inverse clock signals on lines 208 and 210 to two D-type flip-flops 212 and 214. An output from the flip-flop 212 is applied to another clock driver 216, and the clock and inverse clock outputs from said driver are applied on lines 218 and 220. The line 218 is connected to 10 buffers 222, 224, 226, 228 and 230 which are associated with tri-state output drivers 232, 234, 236, 238 and 240, respectively. The line 220 is connected to an output inverter 242 associated with a tri-state output driver 244. Since only the output signals BIOR/ and BIOW/ are of interest in the present invention, only the circuitry associated with these signals in Figs. 4A and 4B will be described. It will be noted that the line carrying input signal RD/ is connected through an inverter 246 to one input of a NAND gate 248. A second input of that gate is connected to the input signal IO-M. The third input to the NAND gate 248 is taken from the output of a NOR gate 250. One input to the NOR gate 250 is taken from the output of the flip-flop 214, and the other input is taken from the output of a NOR gate 252, the inputs of which are connected to conductors on which the signals SO and SI appear. The output of the NAND gate 248 is connected to one input of the 10 buffer 228 associated with the tri-state output driver 238, which is coupled through connecting pad 235 to a termination 237 on which the output signal BIOR/ appears. Operation of the tri- state output driver 238 is controlled by the clock signal emanating from the clock driver 216 and appearing on the conductor 218. Similarly, the 10 buffer 230 associated with the tri-state driver 240, which is coupled through a connecting pad 239 to a termination 241 for the output signal BIOW/, has an input connected to an output from a NAND gate 254 which also has inputs from the NOR gate 250 and the conductor associated with the input signal IO-M. A third input to the NAND gate 250 is an inverted (by inverter 256) signal WR/. Operation of the tri-state output driver 240 is controlled by the clock signal emanating from the clock driver 216 and appearing on the conductor 218. The bus input/output read signal BIOR/ and the bus input/output write signal BIOW/, like the address signal from the address address latch 54, are applied to the AND OR logic circuit 56, which provides output signals CS/, RD/ and WR/. The signal CS/ is a chip select signal which is employed to select the analog-to-digital converter 46, while the RD/ and WR/ signals are read and write signals, respectively, to control the operation of the analog-to-digital converter 46, which reads the differential voltage between reference voltage and analog ground on a read command, and causes such information to be output on a write command. In addition to conductors for signals CS/, RD/, WR/, Vref and analog ground, the analog-to- digital converter is also connected to a digital ground 60. The outputs from the analog-to-digital converter 46 are signals DB2 to DB9 inclusive which appear on correspondingly marked output conductors which are applied to corresponding inputs of a programmable logic array device, or PAL, 62, which may be of type 20L8, manufactured by Monolithic Memories, Santa Clara, California. The PAL 62 may be "read protected", if desired, to insure that the unauthorized reading of the fuse pattern therein cannot occur, and that the decryption of the PAL 62 will thus remain secure. It will be noted that signals DBO and DB1 on correspondingly marked output lines of the analog-to-digital converter 46 are not used in the present invention. Also provided as inputs to the PAL 62 are four outputs from a combinational control 64. These inputs to the PAL 62 control the translation of input signals to output signals to produce a given output signal or signals in response to a given input signal or combination of signals. The combinational control may take several forms. One such form is shown in Fig. 2, in which four inputs 66, 68, 70, 72 are connected by conductors in parallel to a ground connection over a plurality of removable jumpers 74. Each conductor is also connected through a resistor 76 to a +5 volt source of potential. The logic levels of a given input will be at ground if the jumper 74 for the conductor associated with the input is retained in place, but will be at a logic level of ÷5 volts if the jumper is removed. A simple method is thus employed for providing a desired combination of logic control signals to the PAL 62. A second form of combinational control is shown in Fig. 3, in which input signals on a data bus 76 are applied to inputs of a register 78, which may be of type 74ACT574, manufactured by Samsung Semiconductor and Telecommunications Inc., San Jose, California. These signals are used to form output signals on conductors 80, 82, 84, 86 which are applied to the previously described inputs of the PAL 62. The manner in which the data signals are controlled or combined to produce output signals is determined by a signal applied to the register 78 on an output from an AND gate 88 which may be of a type manufactured by Texas Instruments. The AND gate 88 receives a first input from a conductor on which the previously described signal BIOW/ appears, and receives a second input from an AND-OR-INVERT circuit 90, which may be of a type manufactured by Texas Instruments, and which in turn receives inputs from the address bus 52 associated with the microprocessor 50. It will be seen that the signal from the AND gate 88 controls the register 78 to provide a combination of signals for control of the PAL 62. As shown in Fig. 1, the outputs from the PAL 62 are divided into two groups. The lower group of outputs 92, 94, 96, 98 are applied to a block 100, representing other portions of terminal software. These signals may be utilized to control various terminal-associated software functions. An upper group of outputs 102, 104, 106 and 108 provide security information indicating whether or not a key assembly 20 applied to the lock assembly 26 is a proper key assembly for unlocking the lock assembly 26. These signals may also convey additional information, such as the identity of the holder of the key, or the category of employee holding the key, such as clerk, supervisor or programmer. These signals are applied to a block 110, representing other portions of the terminal hardware, and most frequently are used to control the locking or unlocking of the terminal or of certain portions thereof. Thus, one key may unlock only the keyboard to permit operation thereof, while another key may unlock a portion of the terminal which permits alteration of the programming thereof. As an example of use of signals appearing on the outputs 102, 104 106 and 108, the letters X, L, N and S are shown as applied to these respective outputs. The letter X in this example is considered to apply to the programming mode of the terminal, so that an appropriate signal on output 102 would unlock the terminal in such a manner as to permit an alteration of its programming. The letter L in this example may indicate a locked state in which the terminal cannot be operated. An inverse logic level on this line would conversely indicate that the terminal was unlocked and could be operated. Alternatively, the letter L could indicate a load condition in which a program could be entered into the terminal. The letter N in this example may indicate a normal condition under which, like the inverse L conditions, the machine may be operated. Finally, the letter S in this example may indicate a state in which a supervisor may have access to all or a part of the terminal, which access is denied, for example, to a clerk. It will thus be seen that the key assembly 20 and the PAL 62 must, in effect, match. Thus, a matching set of key assemblies 20 and PAL 62 may be utilized, for example, for a given store or chain of stores, while a different matched set of key assemblies 20 and PAL 62 may be utilized for a different store or chain of stores. Another embodiment of the electronic keylock system of the present invention is shown in Fig. 5= This system employs a microcontroller 120 which functionally includes the equivalent of the analog-to- digital converter 46, the PAL 62 of the embodiment of Fig. 1, and the combinational control 64. This embodiment has the advantage of combining several separate components or circuits into one device for greater compactness and economy. It also provides a flexible and software programmable system. In the system of Fig. 1, the customer's keylock definition must be known at the time of building the system so that the PAL can be programmed accordingly when the system is built. The use of the microcontroller in the system of Fig. 5 simplifies the terminal keying configuration by allowing the customer access to software to alter the acceptable keycode information. The customer, rather than the manufacturer, can thus control key selection. One type of microcontroller 120 which can be employed in the present invention is the MC68HC11A8, manufactured by Motorola, Inc. A block diagram of this microcontroller is shown in Fig. 6. It will be noted that an A-D converter 122 is included in the microcontroller. The microcontroller is controlled by - li ¬ the 8085 microprocessor 50 via various signals transmitted over lines represented by the bus 124 in Fig. 5 and by the bracket 125 in Fig. 6. Certain lines of ports A, B and C, designated by reference characters 126, 128 and 130, respectively, provide outputs from the microcontroller 120 to other portions of the terminal hardware, as represented by block 110 of Fig. 1, and the terminal software, as represented by block 100 of Fig. 1. As shown in Fig. 5, a key assembly 132 includes two precision resistors 134 and 136. These are associated with terminations 138 and 140, respectively, and a ground conductor 142 is associated with a third terminal 144. The key assembly 132 is engageable with a jack assembly or receptacle 146 having terminations 148, 150 and 152 corresponding to the terminations 138, 140 and 144. The termination 152 is connected by a conductor 154 to a ground connection 156. The terminations 148 and 150 are connected to nodes 158 and 160. Nodes 158 and 160 are connected through protective resistors 162 and 164 to connections of port E, designated 166, of the microcontroller 120, which, in turn, provides internal connecting paths to the A-D converter 122. An electrostatic discharge protection network 168 is preferably included and is connected to the nodes 158 and 160 and to the ground connection 156. The specific circuitry of such a network is not specifically disclosed herein, but it is believed that a suitable design could readily be developed by one skilled in the art. The protection network 168, together with the resistors 162 and 164, provides protection to the A-D converter 122 of the microcontroller 120. Additional conductors 170 and 172 extend from the nodes 158 and 160 to a pair of 0.1% precision resistors 174 and 176. The specific resistance values of these resistors will be dependent upon the resistances of the key resistors 134 and 136. At their other ends, these resistors are connected to a node 178, and thence, through another node 180 to a V RH connection 182 of the A-D converter 122 in the microcontroller 120. The node 180 is connected through a 1000-ohm precision resistor 184 to a +12- volt precision source of potential 186. Also connected to the node 180 is one side of a 5.00 volt, +0„2% precision zener diode 188, which may be of type LT1029ACZ, manufactured by Linear Technology Corp., Milpitas, California. At its other side, the diode 188 is connected through a node 190 to a ground connection 192. A conductor extends from the node 190 to a VRJ. connection 194 of the A-D converter 122 in microcontroller 120. The microcontroller 120 can be programmed in a well-known manner to internally decode output information from the A-D converter 122 and provide such information to ports 126, 128 and 130 in the same or similar form as output information is provided on the outputs 92, 94, 96, 98 and 102, 104, 106, 108 from the PAL 62 in the embodiment of Fig. 1. This information can then be utilized by portions of the associated point of sale terminal, such as portions 100 and 110 in the embodiment of Fig. 1.

Claims: CLAIMS 1. An electronic lock system, including key receiving means (28; 146) adapted to receive a key (20) which includes resistor means (22; 134, 136) , characterized by measuring means (30-46; 122, 148-194) coupled to said key receiving means (28; 146) and including analog-to-digital conversion means (46; 122) adapted to provide a digital representation of the resistance of said resistor means (22; 134; 136); control means (50, 58, 60; 50, 120) adapted to cause paid analog-to-digital conversion means (46; 122) to provide said digital representation at a desired time; and translation means (62; 120) coupled to said analog-to-digital conversion means (46; 122) and adapted to translate said digital representation into output control signals. 2. An electronic lock system according to claim 1, characterized in that said translation means includes a programmable logic array (62) . 3. An electronic lock system according to claim 2, characterized by further control means (64) adapted to control the operation of said programmable logic array (62) . 4. An electronic lock system according to claim 3, characterized in that said programmable logic array (62) is read protected, thereby preventing unauthorized reading of said programmable logic array (62). 5. An electronic lock system according to any one of the preceding claims, characterized in that said resistor means (22) includes a precision resistor having a tolerance of one per cent or less. 6. An electronic lock system according to claim 5, characterized in that said measuring means includes a precision potential source adapted to maintain a supply voltage to within one per cent of a nominal value. 7. An electronic lock system according to claim 5 or claim 6, characterized in that said precision resistor is contained within a telephone tyP e p3- u forming said key (20). δ. An electronic lock system according to any one of the preceding claims, characterized in that said control signals are adapted to control the operation of a point-of-sale terminal and in that said resistor means (22; 134, 136) is of different value for different classes of key holders. 9. An electronic lock system according to claim 8, characterized in that said different classes include operators, programmers and supervisors. 10. An electronic lock system according to any one of the preceding claims, characterized in that said control means includes a microprocessor (50).

Inventors: REIKER DAVID ALLEN, REIKER, DAVID, ALLEN
Applicants: NCR CO, NCR CORPORATION
Application year: 1988
Main classification: E05B49
IPC codes: E05B49, G07C9