Hardware-driven clock with object-oriented interface

• US 5,526,515 A
• Filed: 06/30/1994
• Issued: 06/11/1996
• Est. Priority Date: 06/30/1994
• Status: Expired due to Term

• Current Assignee: Apple Inc.
• Original Assignee: Taligent, Inc. (HP Inc.)
• Inventors: Ross, Patrick D., Denman, Matthew L., Milne, Steve H.
• Primary Examiner(s): Kriess, Kevin A.
• Assistant Examiner(s): BUTLER, DENNIS
• Application Number:
  US08/269,282
• Time in Patent Office: 712 Days
• Field of Search: 395/550, 364/270, 364/270.2, 364/270.3
• US Class Current: 713/500
• CPC Class Codes: G06F 1/14 Time supervision arrangements, e.g. real time clock

Abstract

Timing apparatus for use with a computer system works with clock hardware which periodically generates a tick update signal. The timing apparatus uses a floating point number to maintain a total tick count for representing absolute time so that both a large range and a high resolution can be accommodated. However, since floating point operations can not always be used at hardware, or interrupt, levels and there are some cases where a hardware-dependent time representation will produce performance gains, a hardware dependent clock system is also provided. The clock system is provided with a flexible interface by using object-oriented programming techniques and providing three clock objects that provide for three different clock representations. Each of the objects provides its own methods for converting between the time representation that it uses and the time representations used by the other objects.

Claims

1. An apparatus for a computer system to generate an absolute time signal with a varying resolution, comprising:

(a) circuitry for periodically generating a tick update signal; and

(b) an apparatus for the representation of an absolute time signal with a varying resolution, comprising;

(1) storage apparatus for storing a zero point number representing the zero point time; and

(2) a time count apparatus for storing an absolute time signal represented as an absolute floating point number based on a predetermined number of tick update signals; and

(c) an update apparatus responsive to each tick update signal for recalculating the absolute floating point number to indicate a number of tick update signals received by the time count apparatus since the zero point time.

2. Timing apparatus according to claim 1, wherein the update apparatus comprises apparatus responsive to each tick update signal for incrementing the absolute floating point number.

3. Timing apparatus according to claim 1, wherein the update apparatus comprises apparatus responsive to each tick update signal for decrementing the absolute floating point number.

4. Timing apparatus according to claim 1, wherein the time count apparatus comprises apparatus responsive to the absolute floating point number for converting the absolute floating point number into a converted real time representation having a predetermined format.

5. Timing apparatus according to claim 4, further comprising apparatus for maintaining a current real time representation having the predetermined format and wherein the time count apparatus further comprises apparatus responsive to the current real time representation for comparing the current real time representation with the converted real time representation to determine a conversion offset value.

6. Timing apparatus according to claim 5, wherein the time count apparatus further comprises apparatus responsive to a real time representation in the predetermined format for converting the real time representation into a real time floating point number.

7. Timing apparatus according to claim 6, wherein the apparatus for converting the real time representation into a real time floating point number comprises apparatus for retrieving the conversion offset value;

apparatus responsive to the retrieved conversion offset value for subtracting the retrieved offset value from the real time representation to generate a corrected real time value and apparatus responsive to the corrected real time value for converting the corrected real time value to a

8. An apparatus for an object-oriented computer system to generate an absolute time signal with a varying resolution, comprising:

(a) circuitry for periodically generating a tick update signal;

(b) storage apparatus;

(c) a first real time clock object representing an absolute time signal with a varying resolution, comprising;

(1) data including a zero point number stored in the storage apparatus which zero point number represents a zero point time; and

(2) an absolute floating point number stored in the storage apparatus representing the absolute time signal based on a predetermined number of tick update signals; and

(d) a first method responsive to each tick update signal for recalculating the absolute floating point number to indicate a number of tick update signals received by the time count apparatus since the zero point time.

9. Timing apparatus according to claim 8, wherein the first real time clock object comprises a second method responsive to each tick update signal for incrementing the absolute floating point number.

10. Timing apparatus according to claim 8, wherein the first real time clock object comprises a third method responsive to each tick update signal for decrementing the absolute floating point number.

11. Timing apparatus according to claim 8, wherein the first real time clock object further comprises a fourth method responsive to the absolute floating point number for converting the absolute floating point number into a converted real time representation having a predetermined format.

12. Timing apparatus according to claim 11, including a second real time clock object for maintaining a current real time representation having the predetermined format and wherein the first real time clock object further comprises a fifth method responsive to the current real time representation for comparing the current real time representation with the converted real time representation to determine a conversion offset value.

13. Timing apparatus according to claim 12, wherein the first real time clock object further comprises a sixth method responsive to a real time representation in the predetermined format for converting the real time representation into a real time floating point number.

14. Timing apparatus according to claim 13, wherein the sixth method comprises a seventh method for retrieving the conversion offset value;

an eighth method responsive to the retrieved conversion offset value for subtracting the retrieved offset value from the real time representation to generate a corrected real time value and a ninth method responsive to the corrected real time value for converting the corrected real time value to a real time floating point number.

15. Timing apparatus according to claim 8, further comprising a hardware clock object comprising data including a zero point number stored in the storage apparatus which zero point number represents a zero point time and an absolute integer number stored in the storage apparatus which absolute integer number represents the absolute time signal;

and a tenth method responsive to each tick update signal for recalculating the absolute integer number to indicate a number of tick update signals received by the time count apparatus since the zero point time.

16. Timing apparatus according to claim 15, wherein the hardware clock object comprises an eleventh method responsive to each tick update signal for incrementing the absolute integer number.

17. Timing apparatus according to claim 15, wherein the hardware clock object comprises a twelfth method responsive to each tick update signal for decrementing the absolute integer number.

18. Timing apparatus according to claim 15, wherein the hardware clock object comprises a thirteenth method responsive to the absolute integer number for converting the absolute integer number into a converted real time representation having a predetermined format.

19. A method for generating an absolute time signal with a varying resolution in a computer system, the method comprising the steps of:

(a) periodically generating a tick update signal;

(b) storing a zero point number which represents a zero point time;

(c) storing an absolute floating point number as the absolute time signal which absolute time signal has a varying resolution based on a predetermined number of tick update signals; and

(d) recalculating the absolute floating point number in response to each tick update signal so that the absolute floating point number represents the number of tick update signals generated since the zero point time.

20. A method according to claim 19, wherein step (d) includes the step of incrementing the absolute floating point in response to each tick update signal.

21. A method according to claim 19, wherein step (d) comprises the step of decrementing the absolute floating point number in response to each tick update signal.

22. A method according to claim 19, further comprising the step of converting the absolute floating point number into a converted real time representation having a predetermined format.

23. A method according to claim 22, including the step of comparing the current real time representation with the converted real time representation to determine a conversion offset value.

24. A method according to claim 23, further comprising the step of converting the converted real time representation into a real time floating point number.

25. A method according to claim 24, including the steps of:

(a) retrieving the conversion offset value;

(b) subtracting the retrieved conversion offset value from the real time representation to generate a corrected real time value; and

(c) converting the corrected real time value to a real time floating point number.