Hour meter apparatus and method

• US 4,617,639 A
• Filed: 08/08/1984
• Issued: 10/14/1986
• Est. Priority Date: 08/08/1984
• Status: Expired due to Fees

• Current Assignee: Caterpillar Industrial Incorporated Mentor Ohio
• Original Assignee: Caterpillar Incorporated
• Inventors: Paine, John C.
• Primary Examiner(s): NOT, DEFINED
• Application Number:
  US06/638,913
• Time in Patent Office: 797 Days
• Field of Search: 364/569, 364/144, 364/143, 364/424, 364/551, 377/20, 340/52 D, 340/52 R
• US Class Current: 701/35
• CPC Class Codes: G07C 5/04 using counting means or digital clocks
• CPC Class Codes: H03K 21/403 Arrangements for storing the counting state in case of power supply interruption

Abstract

Electronic hourmeter devices having non-volatile memories are useful, for example, in industrial vehicles. Advantageously, such non-volatile memories should be free from a need for battery back-up systems and should minimize the number of changes of the internal memory registers. The subject electronic hourmeter apparatus includes both a dynamic memory device and a non-volatile memory device. Data is maintained in each of the memory devices and memory bit changes are minimized by utilizing a gray coded binary representation of a portion of the data and by systematically altering the addressed memory location of a portion of the data in response to one of the stored data values. Data storage occurs both periodically and in response to disconnection of the vehicle battery. Thus, the disclosed electronic hourmeter apparatus 10 advantageously maintains the integrity of the stored data, minimizes the number of bit changes that occur in the non-volatile memory device, and avoids the need for a battery back-up.

Claims

1. Apparatus for measuring, storing and displaying the accumulated period of time an intermittent operating condition of a vehicle exists, comprising:

means for detecting said intermittent operating condition and producing a control signal in response to said detected condition;

oscillator means for producing a predetermined clock frequency signal;

a dynamic memory device having a plurality of addressable memory locations;

a non-volatile memory device having a plurality of addressable memory locations;

a plurality of time interval registers; and

,

processor means for receiving said control signal and said clock frequency signal, controllably modifying predetermined ones of said plurality of time interval registers in response to receiving both said control signal and a predetermined number of cycles of said clock frequency signal, storing a representation of the contents of said time interval registers in said dynamic memory device in response to each modification of a first predetermined one of said time interval registers, and transferring the contents of said dynamic memory device to said non-volatile memory device in response to each modification of a second predetermined one of said time interval registers.

2. Apparatus, as set forth in claim 1, wherein said vehicle includes a vehicle battery and said apparatus includes means for sensing the vehicle battery voltage and transferring the contents of said dynamic memory device to said non-volatile memory device in response to said vehicle battery voltage being less than a predetermined magnitude.

3. Apparatus, as set forth in claim 1, wherein a representation of the contents of at least a first one of said time interval registers is stored in both said dynamic and non-volatile memory devices as a binary coded decimal number, and a representation of the contents of at least a second one of said time interval registers is stored in both said dynamic and non-volatile memory devices as a gray coded binary number.

4. Apparatus, as set forth in claim 3, wherein the addressable memory location in which at least one of said gray coded binary numbers is stored is selected in response to the value of a predetermined different one of said stored numbers.

5. Apparatus, as set forth in claim 4, wherein the addressable memory location in which at least one of said gray coded binary numbers is stored varies systematically in response to said different one of said stored numbers.

6. Apparatus for measuring, storing and displaying the accumulated period of time an intermittent operating condition of a vehicle exists, comprising:

means for detecting said intermittent operating condition and producing a control signal in response to said detected condition;

oscillator means for producing a predetermined clock frequency signal;

a non-volatile memory device having a plurality of addressable memory locations;

a plurality of time interval registers, the contents of each of said time registers representing a different predetermined time interval; and

,

processor means for receiving said control signal and said clock frequency signal, accumulating the number of cycles of said clock frequency signal in said time interval registers in response to receiving both said control signal and said clock frequency signal, and periodically storing a binary coded decimal representation of the contents of at least a first one of said time registers and a gray coded representation of at least a second one of said time registers in said non-volatile memory device.

7. Apparatus, as set forth in claim 6, wherein said periodic storage occurs in response to the content of one of said time registers.

8. Apparatus, as set forth in claim 7, wherein said vehicle includes a vehicle battery and said apparatus includes means for sensing the vehicle battery voltage and storing said representations of the contents of said time interval registers in said non-volatile memory device in response to said vehicle battery voltage being less than a predetermined magnitude.

9. Apparatus, as set forth in claim 8, including means for controllably accessing and decoding the contents of said dynamic memory and displaying a number representing said decoded value.

10. An hourmeter for a vehicle, said vehicle having a vehicle battery, comprising:

a switch connected to said battery;

a first voltage regulator having an input terminal connected through said switch to said battery and an output terminal;

a microprocessor having a plurality of input, output, and input/output ports, one of said input ports being connected to said voltage regulator output terminal;

a dynamic random access memory device connected to one of said microprocessor input/output ports;

a non-volatile random access memory device connected to said dynamic random access memory device and to said microprocessor; and

,

a digital display device connected to one of said microprocessor output ports.

11. An hourmeter, as set forth in claim 10, including a second voltage regulator having an input terminal connected to said vehicle battery and first and second output terminals, said first output terminal being connected to said non-volatile random access memory device;

and,

a voltage sensing circuit having a first input terminal connected to said voltage regulator second output terminal, a second input terminal connected to said vehicle battery, and an output terminal connected to said non-volatile random access memory device.

12. A method for measuring, storing and displaying the accumulated period of time an intermittent operating condition of a vehicle exists, said vehicle having a vehicle battery, comprising the steps of:

detecting said intermittent operating condition and producing a control signal in response to said detected condition;

producing a predetermined clock frequency signal;

receiving said control signal and said clock frequency signal;

modifying predetermined ones of a plurality of time interval registers in response to receiving both said control signal and a predetermined number of cycles of said clock frequency signal, storing a representation of the contents of said time interval registers in a dynamic memory device in response to each modification of a first predetermined one of said time interval registers; and

,

transferring the contents of said dynamic memory device to a non-volatile memory device in response to each modification of a second predetermined one of said time interval registers.

13. A method, as set forth in claim 12, including the steps of sensing the vehicle battery voltage and transferring the contents of said dynamic memory device to said non-volatile memory device in response to said vehicle battery voltage being less than a predetermined magnitude.

14. A method, as set forth in claim 12, including the steps of storing a representation of the contents of at least a first one of said time interval registers in both said dynamic and non-volatile memory devices as a binary coded decimal number, and storing a representation of the contents of at least a second one of said time interval registers in both said dynamic and non-volatile memory devices as a gray coded binary number.