Power saving scheme for a digital wireless communications terminal

• US 6,029,061 A
• Filed: 03/11/1997
• Issued: 02/22/2000
• Est. Priority Date: 03/11/1997
• Status: Expired due to Term

• Current Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Kohlschmidt, Peter
• Primary Examiner(s): Nguyen, Lee
• Application Number:
  US08/816,013
• Time in Patent Office: 1,078 Days
• Field of Search: 455/502, 455/343, 455/38.3, 455/574, 455/208, 455/255, 455/257, 455/258, 455/259, 455/260, 455/265, 331/2, 331/18, 331/25, 331/49, 340/825.44, 370/311, 370/324, 375/354, 375/359, 375/374, 713/400, 395/500, 395/502, 395/503, 327/141, 327/144, 327/145, 327/151, 327/160, 368/156, 368/157, 326/93, 326/96
• US Class Current: 455/574
• CPC Class Codes: H04W 52/029 reducing the clock frequency of the controller
• CPC Class Codes: H04W 52/0293 having a sub-controller with a low clock frequency switching on and off a main controller with a high clock frequency
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

According to the present invention, a mobile communications terminal includes a high accuracy clock for providing a timebase in a normal operating mode, a "slow clock" for providing the timebase in a low power mode of operation, and at least one processor coupled to the high accuracy clock and the "slow clock" for controlling the modes of operation. In a preferred embodiment, the mobile communications terminal includes a conversion signal processor (CSP), a digital signal processor (DSP), a communications protocol processor, and a radio frequency (RF) segment. The CSP, which includes a plurality of registers, interfaces with the DSP to execute the timing control functions for the terminal. In the normal operating mode, the timebase is maintained from the high accuracy clock. During inactive periods of terminal operation (e.g., in a paging mode), a sleep mode is enabled wherein the high accuracy clock source is disabled, the DSP, CSP, and communications protocol processor are shut down, and the "slow clock" provides the timebase for the terminal while a sleep counter is decremented for a given sleep interval. Upon expiration of the sleep interval or in response to an intervening external event (e.g., a keypad is depressed), a terminal wake-up is initiated so that the high accuracy clock resumes control of the timebase. Because the high accuracy clock and the "slow clock" are not synchronized, the CSP and DSP calibrate the "slow clock" to the high accuracy clock prior to the terminal entering the sleep mode.

Claims

1. A clock circuit comprising:

at least two asynchronous clock sources, including

a high accuracy clock source for maintaining a timebase in a first mode, and

a low power clock source for maintaining the timebase in a second mode for a given time interval; and

a conversion signal processor having a plurality of registers including an accumulator and a multi-function register, said conversion signal processor coupled to said high accuracy clock source and said low power clock source, said conversion signal processor being operable to calibrate said low power clock source with said high accuracy clock source prior to entering said second mode and to disable said high accuracy clock source during said second mode, said conversion signal processor includes a counter operable to decrement said given time interval according to clock cycles from said low power clock source;

wherein said accumulator is operable to increment according to clock cycles from said high accuracy clock source while said multi-function register is operable to simultaneously decrement a given calibration time period according to clock cycles from said low power clock source.

2. The clock circuit according to claim 1, wherein said high accuracy clock source is a crystal-based clock and said low power clock source is a crystal-based clock having a lower operating frequency relative to said high accuracy clock source.

3. The clock circuit according to claim 1, further comprising a digital signal processor coupled to said conversion signal processor, wherein contents of said plurality of registers are mapped to memory locations in said digital signal processor, said digital signal processor and said conversion signal processor being operable to control timing functions of the clock circuit using said registers.

4. The clock circuit according to claim 3, wherein said digital signal processor is operable to calibrate said low power clock source to said high accuracy clock source using said contents of said accumulator and said multi-function register.

5. The clock circuit according to claim 4, wherein said digital signal processor being operable to identify a timing relationship based on a resulting value in said accumulator.

6. The clock circuit according to claim 5, wherein selected functions in said conversion signal processor, said digital signal processor, and said high accuracy clock source are disabled during said second mode, said given time interval being representative of a sleep interval.

7. The clock circuit according to claim 6, wherein said digital signal processor is responsive to a wake-up signal from said conversion signal processor at the expiration of said sleep interval, said digital signal processor being further operable to update said timebase using said timing relationship and said sleep interval, and said high accuracy clock source being operable to maintain said updated timebase upon said counter being decremented to a zero value.

8. The clock circuit according to claim 6, wherein said digital signal processor is responsive to a wake-up signal from said conversion signal processor prior to the expiration of said sleep interval, said plurality of registers further comprising a shadow counter, said shadow counter cooperating with said counter to store an actual sleep interval, said digital signal processor being further operable to update said timebase using said timing relationship and said actual sleep interval, and said high accuracy clock source being operable to maintain said updated timebase.

9. A cellular communications terminal, comprising:

at least two asynchronous clock sources, including

a high accuracy clock source for maintaining a timebase in a first mode, and

a low power clock source for maintaining the timebase in a second mode for a given time interval;

a conversion signal processor having a plurality of registers including an accumulator and a multi-function register, said conversion signal processor coupled to said high accuracy clock source and said low power clock source, said conversion signal processor being operable to calibrate said low power clock source with said high accuracy clock source prior to entering said second mode and to disable said high accuracy clock source during said second mode, said conversion signal processor includes a counter operable to decrement said given time interval according to clock cycles from said low power clock source; and

a radio frequency segment coupled to said high accuracy clock source and said conversion signal processor;

wherein said accumulator is operable to increment according to clock cycles from said high accuracy clock source while said multi-function register is operable to simultaneously decrement a given calibration time period according to said clock cycles from said low power clock source.

10. The cellular communications terminal according to claim 9, wherein said high accuracy clock source is a crystal-based clock and said low power clock source is a crystal-based clock having a lower operating frequency relative to said high accuracy clock source.

11. The cellular communications terminal according to claim 9, further comprising:

a digital signal processor coupled to said conversion signal processor, wherein contents of said plurality of registers are mapped to memory locations in said digital signal processor, said digital signal processor and said conversion signal processor being operable to control timing functions of the clock circuit using said registers; and

a communications processor coupled to said digital signal processor and to said high accuracy clock source, said communications processor being operable to perform general processing functions of the terminal.

12. The cellular communications terminal according to claim 11, wherein said digital signal processor is operable to calibrate said low power clock source to said high accuracy clock source using said contents of said accumulator and said multi-function register.

13. The cellular communications terminal according to claim 12, wherein said digital signal processor being operable to identify a timing relationship based on a resulting value in said accumulator.

14. The cellular communications terminal according to claim 9, wherein selected functions in said conversion signal processor, said digital signal processor, said communications processor, said radio frequency segment, and said high accuracy clock source are disabled during said second mode, said given time interval being representative of a sleep interval.

15. The cellular communications terminal according to claim 14, wherein said digital signal processor is responsive to a wake-up signal from said conversion signal processor at the expiration of said sleep interval, said digital signal processor being further operable to update said timebase using said timing relationship and said sleep interval, and said high accuracy clock source being operable to maintain said updated timebase upon said counter being decremented to a zero value.

16. The cellular communications terminal according to claim 14, wherein said digital signal processor is responsive to a wake-up signal from said conversion signal processor prior to the expiration of said sleep interval, said plurality of registers further comprising a shadow counter, said shadow counter cooperating with said counter to store an actual sleep interval, said digital signal processor being further operable to update said timebase using said timing relationship and said actual sleep interval, and said high accuracy clock source being operable to maintain said updated timebase.

17. A power saving method, comprising the steps of:

maintaining a timebase in a first mode using a high accuracy clock source;

maintaining the timebase in a second mode for a given time interval using a low power clock source;

calibrating said low power clock source with said high accuracy clock source prior to entering said second mode;

disabling said high accuracy clock source via a programmable processor upon entering said second mode;

decrementing said given time interval according to clock cycles from said low power clock source;

simultaneously incrementing an accumulator according to clock cycles from said high accuracy clock source while decrementing a given calibration time period according to said clock cycles from said low power clock source; and

identifying a timing relationship based on a resulting value in said accumulator.

18. The power saving method according to claim 17, further comprising the step of disabling selected functions of said programmable processor during said second mode, wherein said given time interval is representative of a sleep interval.

19. The power saving method according to claim 18, further comprising the steps of:

providing a wake-up signal to said programmable processor at the expiration of said sleep interval;

calculating an updated timebase in said programmable processor using said timing relationship and said sleep interval; and

maintaining said updated timebase using said high accuracy clock source at the expiration of said sleep interval.

20. The power saving method according to claim 18, further comprising the steps of:

providing a wake-up signal to said programmable processor prior to the expiration of said sleep interval;

measuring an actual sleep interval based on timing of said wake-up signal being provided to said programmable processor;

calculating an updated timebase in said programmable processor using said timing relationship and said actual sleep interval; and

maintaining said updated timebase using said high accuracy clock source at the expiration of said actual sleep interval.

21. A method of operating a cellular communications terminal, comprising the steps of:

maintaining a timebase in a first mode using a high accuracy clock source;

maintaining the timebase in a second mode for a given time interval using a low power clock source;

calibrating said low power clock source with said high accuracy clock source prior to entering said second mode;

disabling said high accuracy clock source via a conversion signal processor upon entering said second mode;

decrementing said given time interval according to clock cycles from said low power clock source;

simultaneously incrementing an accumulator in said conversion signal processor according to clock cycles from said high accuracy clock source while decrementing a given calibration time period according to said clock cycles from said low power clock source; and

identifying a timing relationship using a digital signal processor based on a resulting value in said accumulator.

22. The method according to claim 21, further comprising the step of disabling selected functions of said conversion signal processor and said digital signal processor during said second mode, wherein said given time interval is representative of a sleep interval.

23. The method according to claim 22, further comprising the steps of:

providing a wake-up signal to said digital signal processor at the expiration of said sleep interval;

calculating an updated timebase in said digital signal processor using said timing relationship and said sleep interval; and

maintaining said updated timebase using said high accuracy clock source at the expiration of said sleep interval.

24. The method according to claim 22, further comprising the steps of:

providing a wake-up signal to said digital signal processor prior to the expiration of said sleep interval;

measuring an actual sleep interval based on timing of said wake-up signal being provided to said digital signal processor;

calculating an updated timebase in said digital signal processor using said timing relationship and said actual sleep interval; and

maintaining said updated timebase using said high accuracy clock source at the expiration of said actual sleep interval.

25. A clock circuit comprising:

at least two asynchronous clock sources, including

a high accuracy clock source for maintaining a timebase in a first mode, and

a low power clock source for maintaining the timebase in a second mode for a given time interval; and

a digital device having a first register and a second register coupled to said high accuracy clock source and said low power clock source, said digital device being operable to calibrate said low power clock source with said high accuracy clock source prior to entering said second mode, said digital device includes a counter operable to decrement said given time interval according to clock cycles from said low power clock source;

wherein said first register is operable to increment according to clock cycles from said high accuracy clock source while said second register is operable to simultaneously decrement a given calibration time period according to clock cycles from said low power clock source.

26. The clock circuit according to claim 25 further comprising said digital device being operable to disable said high accuracy clock source during said second mode.

27. The clock circuit according to claim 25 wherein said first register is an accumulator.

28. The clock circuit according to claim 25 wherein said second register is a multifunctional register.

29. The clock circuit according to claim 25 wherein said digital device is a conversion signal processor.

30. A cellular communications terminal, comprising:

at least two asynchronous clock sources, including

a high accuracy clock source for maintaining a timebase in a first mode, and

a low power clock source for maintaining the timebase in a second mode for a given time interval;

a digital device having a first register and a second register, said digital device coupled to said high accuracy clock source and said low power clock source, said digital device being operable to calibrate said low power clock source with said high accuracy clock source prior to entering said second mode and to disable said high accuracy clock source during said second mode, said digital device includes a counter operable to decrement said given time interval according to clock cycles from said low power clock source; and

a radio frequency segment coupled to said high accuracy clock source and said digital device;

wherein said first register is operable to increment according to clock cycles from said high accuracy clock source while said second register is operable to simultaneously decrement a given calibration time period according to said clock cycles from said low power clock source.

31. The cellular communication terminal according to claim 30 further comprising said digital device being operable to disable said high accuracy clock source during said second mode.

32. The cellular communications terminal according to claim 30 wherein said first register is an accumulator.

33. The cellular communications terminal according to claim 30 wherein said second register is a multifunctional register.

34. The cellular communications terminal according to claim 30 wherein said digital device is a conversion signal processor.

35. A power saving method comprising the steps of:

maintaining a timebase in a first mode using a high accuracy clock source;

maintaining the timebase in a second mode for a given time interval using a low power clock source;

calibrating said low power clock source with said high accuracy clock source prior to entering said second mode;

decrementing said given time interval according to clock cycles from said low power clock source;

simultaneously incrementing a first register according to clock cycles from said high accuracy clock source while decrementing a given calibration time period according to said clock cycles from said low power clock source; and

identifying a timing relationship based on a resulting value in said first register.

36. The power saving method according to claim 35 further comprising the step of disabling said high accuracy clock source upon entering said second mode.

37. The power saving method according to claim 35 wherein said first register is an accumulator.

38. A method of operating a cellular communications terminal, comprising the steps of:

maintaining a timebase in a first mode using a high accuracy clock source;

maintaining the timebase in a second mode for a given time interval using a low power clock source;

calibrating said low power clock source with said high accuracy clock source prior to entering said second mode;

decrementing said given time interval according to clock cycles from said low power clock source;

simultaneously incrementing a first register according to clock cycles from said high accuracy clock source while decrementing a given calibration time period according to said clock cycles from said low power clock source; and

identifying a timing relationship based on a resulting value in said first register.

39. The method of operating a cellular communications terminal according to claim 38 further comprising the step of disabling said high accuracy clock source upon entering said second mode.

40. The method of operating a cellular communications terminal according to claim 38 wherein said first register is an accumulator.