Patent Document

CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part (CIP) of U.S. patent application entitled “Communication System and Oscillation Signal Provision Method,” Ser. No. 11/748,004, filed on May 14, 2007, which claims the priority of US provisional application entitled “Common Oscillator In Mobile Station,” Ser. No. 60/806,135, filed on Jun. 29, 2006, the entirety of which are incorporated by reference herein. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to mobile phone systems, and more particularly, to a common oscillation source simultaneously serving multiple communication chips in one device. 
     2. Description of the Related Art 
       FIG. 1  shows a conventional communication system  100 . Currently, mobile phones provide various functionalities in addition to telephone communication. For example, in  FIG. 1 , a mobile module  110 , a Bluetooth module  120  and a WiFi module  130  are simultaneously implemented in one device, each operating at different frequencies. Specifically, according to known power saving technologies, these modules may operate in either a busy mode or an idle mode, with different frequency sources required. The mobile module  110  uses a first high oscillator  112  for busy mode, and an oscillation source  114  for idle mode. Likewise, the Bluetooth module  120  and WiFi module  130  also require corresponding high and low frequency oscillators  122 ,  132 ,  124  and  134  in either mode. The disadvantage of the architecture is that since two oscillators are required for each module, circuit redundancies and costs proportionally increase when multiple modules are implemented together. Additionally, the total power consumption of the oscillators is significant. When all modules are operating in the busy mode, a power shortage may quickly occur, reducing the mobility of the communication system  100 . Thus, a more efficient architecture is desirable. 
     BRIEF SUMMARY OF THE INVENTION 
     An embodiment of a communication system is provided, in which a high frequency oscillator generates a first high frequency signal upon receipt of no disable signal. The first high frequency signal is commonly shared by at least two modules. Each module coupled to the high frequency oscillator operates in either busy or idle mode, wherein the module operates at the first high frequency signal when in busy mode, and asserts a request signal when in idle mode. A disablement unit, coupled to the first and second modules, asserts the disable signal to the high frequency oscillator when all of the request signals are asserted, thereby forcing the high frequency oscillator to cease the generation of the first high frequency signal. 
     Another embodiment provides an oscillation signal provision method based on the communication system described, with detailed description given in the following embodiments with reference to the accompanying drawings. 
     An embodiment of a communication system is provided, in which a high frequency oscillator generates a first high frequency signal upon receipt of an enable signal. The first high frequency signal is commonly shared by at least two modules. Each module coupled to the high frequency oscillator operates in either busy or idle mode, wherein the module operates at the first high frequency signal when in busy mode, and asserts a request signal when in idle mode. A enablement unit, coupled to the modules, asserts the enable signal to the high frequency oscillator when at least one request signal is asserted. The high frequency oscillator ceases the generation of the first high frequency signal when the enable signal is not asserted. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein: 
         FIG. 1  shows a conventional communication system; 
         FIGS. 2   a ,  2   b ,  10   a  and  10   b  show embodiments of communication systems according to the invention; 
         FIGS. 3 ,  6 ,  8  and  9  show embodiments of enablement units according to the invention; 
         FIGS. 4 and 16  show exemplary waveforms of the enable signals and auto frequency control (AFC) signals; and 
         FIGS. 5 and 17  are flowcharts of embodiments of oscillation signal provision methods. 
         FIG. 7  shows an exemplary look-up table associated with the embodiment of the enablement unit of  FIG. 6  according to the invention; 
         FIGS. 11 ,  13 ,  14  and  15  show embodiments of disablement units according to the invention; 
         FIG. 12  shows an exemplary look-up table associated with the embodiment of the disablement unit of  FIG. 11  according to the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following description is of the best-contemplated mode of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims. 
       FIGS. 2   a  and  2   b  show embodiments of communication systems  200  and  201  according to the invention. In  FIG. 2   a , a communication system  200  comprises a first module  210 , a second module  220  and a third module  230  sharing one high frequency oscillator  202  and one low frequency oscillator  204 . The high frequency oscillator  202  generates first high frequency signal #HCLK 1  for operations in busy mode, and the low frequency oscillator  204  generates a low frequency signal #LCLK for idle mode. The high frequency oscillator  202  is enabled by an enable signal #en sent from an enablement unit  206  coupled to the first module  210 , second module  220  and third module  230 . When one of the first module  210 , second module  220  and third module  230  switches to busy mode, a corresponding one of request signals #en 1 , #en 2  or #en 3  is delivered to the enablement unit  206 . The enable signal #en is asserted if any of the request signals #en 1 , #en 2  and #en 3  is asserted, and the high frequency oscillator  202  is enabled to generate the first high frequency signal #HCLK 1 . Conversely, if none of the request signals #en 1 , #en 2  and #en 3  is asserted, the enable signal #en is not sent to enable the high frequency oscillator  202 , and the high frequency oscillator  202  may cease to work, reducing the total power consumption of the communication system  200 . Since the high frequency oscillator  202  is simultaneously coupled to multiple modules, the pushing power of the first high frequency signal #HCLK 1  is important. The high frequency oscillator  202  comprises a first high oscillator  112  as a source of the first high frequency signal #HCLK 1 , and a first buffer  250  coupled to the first high oscillator  112 . The first high frequency signal #HCLK 1  is amplified to gain the pushing power before output to the first module  210 , second module  220  and third module  230 . Likewise, the low frequency oscillator  204  comprises an oscillation source  114  as a source of the low frequency signal #LCLK, and a second buffer  260  coupled to the oscillation source  114 , amplifying the low frequency signal #LCLK to gain the pushing power thereof. When any of the first module  210 , second module  220  or third module  230  switches to idle mode, the low frequency signal #LCLK is used for corresponding operations. 
     Alternatively in the communication system  201  of  FIG. 2   b , the low frequency signal #LCLK is provided by oscillation source  114  specially coupled to the first module  210 . The second buffer  260  as shown in  FIG. 2   a  is removed, and the low frequency signal #LCLK is amplified by the first module  210  before outputting via an output terminal L_OUT 1 , from which the second module  220  and third module  230  receives the low frequency signal #LCLK for idle mode operations. Generally, the low frequency signal #LCLK may range from 32 KHz to 32.768 KHz, and accuracy thereof is not strictly required. The range of low frequency signal #LCLK is not limited, and any frequency below 100 KHz may be covered to be the low frequency signal #LCLK. Conversely, the first high frequency signals #HCLK 1 , #HCLK 2  and #HCLK 3  used in busy mode are required to be accurate. The first module  210  may be a mobile phone chip following communication standard such as Global System for Mobile Communication (GSM), General Packet Radio Service (GPRS), and Enhanced Data rates for GSM Evolution (EDGE), Wideband Code Division Multiple Access (WCDMA) or Code Division Multiple Access (CDMA), and the first high frequency signal #HCLK 1  is for example, 13 MHz. The second module  220  may be a Bluetooth chip using a second high frequency signal #HCLK 2  of, for example, 16 MHz, and the third module  230  may be a WiFi chip using a third high frequency signal #HCLK 3  of, for example, 20 MHz. Thus, the first high frequency signal #HCLK 1  sent to the second module  220  and third module  230  should be converted before use. For example, the second module  220  may comprise a first PLL circuit  222 , converting the first high frequency signal #HCLK 1  to the second high frequency signal #HCLK 2 , and a Bluetooth module  120  coupled to the first PLL circuit  222 , operating at the second high frequency signal #HCLK 2  when in busy mode. Similarly, the third module  230  comprises a second PLL circuit  232  to generate the third high frequency signal #HCLK 3  from the first high frequency signal #HCLK 1 , and a WiFi module  130  performing WiFi operations at the third high frequency signal #HCLK 3  when in busy mode. 
       FIG. 3  shows an embodiment of an enablement unit  206  according to  FIGS. 2   a  and  2   b . Since the enable signal #en is asserted when any of the request signals #en 1 , #en 2  and #en 3  is asserted, the enablement unit  206  may be implemented by OR gates  310 ,  320  and  330  serially cascaded, each receiving a corresponding enable signal. Based on the serially coupled architecture, the number of OR gates may be extended if more than three modules are implemented in the communication system  200  or  201 . As shown in  FIGS. 2   a  and  2   b , the first module  210  comprises an auto frequency controller  208  controlling the accuracy of first high frequency signal #HCLK 1 . The first module  210  usually works in a mobile environment with varying effects, thus auto frequency control (AFC) is required to adjust the first high frequency signal #HCLK 1  to adapt the frequency variations in communication. The auto frequency controller  208  generates an adjustment signal #AFC to fine tune the high frequency oscillator  202 . The auto frequency controller  208  is triggered when the first request signal #en 1  is asserted. In the embodiment, the adjustment signal #AFC is generated based on the enable signal #en. 
       FIG. 4  shows a waveform of the enable signals and the adjustment signals. The voltage curves AFC_A and AFC_B show voltage states of the adjustment signal #AFC in two conventional cases based on the architecture in  FIG. 1 . When the first request signal #en 1  is asserted, the voltages AFC_A and AFC_B rapidly wobble as the auto frequency control proceeds. When the first request signal #en 1  is disabled, the voltage AFC_A stays at a constant high level, whereas the voltage AFC_B is uncharged to a low level. If the voltages AFC_A and AFC_B are used in the architecture of  FIGS. 2   a  and  2   b , disadvantages may occur. In the intervals I d  where all the request signals #en 1 , #en 2  and #en 3  are not active, the voltage AFC_A staying high is considered wasteful. Additionally, in the intervals I e  where request signals #en 2  or #en 3  are enabled, the voltage AFC_B of low level causes the high frequency oscillator  202  to generate inaccurate first high frequency signal #HCLK 1 . To solve the disadvantages, the auto frequency controller  208  in  FIGS. 2   a  and  2   b  is triggered based on the enable signal #en sent from the enablement unit  206 , and the voltage status of the adjustment signal #AFC is shown as voltage AFC_C. When any of the request signals #en 1 , #en 2  and #en 3  is enabled, the enable signal #en is enabled, and the voltage AFC_C is sent as the adjustment signal #AFC to maintain the accuracy of first high frequency signal #HCLK 1 . During the intervals I d  where none of the request signals #en 1 , #en 2  and #en 3  are asserted, the voltage AFC_C is uncharged to reduce the power consumption. 
       FIG. 5  is a flowchart of the oscillation signal provision method. The low frequency signal #LCLK is generated in step  510 . In step  502 , it is determined whether the enable signal #en has been asserted. If so, the first high frequency signal #HCLK 1  is generated in step  504 . In step  506 , any of the first module  210 , second module  220  and third module  230  which operates in busy mode utilizes the first high frequency signal #HCLK 1  while the remainder of the first module  210 , second module  220  and third module  230  which operates in idle mode utilizes the low frequency signal #LCLK. If the enable signal #en is not asserted, all of the first module  210 , second module  220  and third module  230  are in idle mode, and as shown in step  512 , all of them operate at the low frequency signal #LCLK. 
       FIG. 6  shows an embodiment of the enablement unit  206  as shown in  FIG. 2   a  or  2   b . The enablement unit  206  may contain at least a buffer  620  storing a look-up table, and a control unit  610  selectively asserts the enable signal #en according to the request signals #en 1 , #en 2  and #en 3  and the stored look-up table. An exemplary look-up table can be shown in  FIG. 7 , in which “1” represents assertion. With reference to the look-up table, the control unit  410  asserts the enable signal #en when at least one of the request signal #en 1 , #en 2  and #en 3  is asserted. The buffer  620  may be implemented in registers, random access memory (RAM), read only memory (ROM), flash memory or others.  FIG. 8  shows an embodiment of the enablement unit  206  as shown in  FIG. 2   a  or  2   b . Since the enable signal #en is asserted when any of the request signals #en 1 , #en 2  and #en 3  is asserted, the enablement unit  206  may be implemented by NAND gates  810 ,  820  and  830  serially cascaded with corresponding pairs of input inverters  811  and  812 ,  821  and  822 , and  831  and  832 , each receiving a corresponding enable signal. Based on the serially coupled architecture, the number of NAND gates with corresponding pairs of input inverters may be extended if more than three modules are implemented in the communication system  200  or  201 .  FIG. 9  shows an embodiment of the enablement unit  206  as shown in  FIG. 2   a  or  2   b . Since the enable signal #en is asserted when any of the request signals #en 1 , #en 2  and #en 3  is asserted, the enablement unit  206  may be implemented by NOR gates  910 ,  920  and  930  serially cascaded with corresponding output inverters  911 ,  921 , and  931 , each receiving a corresponding enable signal. Based on the serially coupled architecture, the number of NOR gates with corresponding output inverters may be extended if more than three modules are implemented in the communication system  200  or  201 . Those skilled in the art may implement similar but different logic circuits in the enablement unit  206 . 
       FIGS. 10   a  and  10   b  show embodiments of communication systems  200  and  201  according to the invention. In  FIG. 10   a , a communication system  200  comprises a first module  211 , a second module  220  and a third module  230  sharing one high frequency oscillator  202  and one low frequency oscillator  204 . Certain details of the high frequency oscillator  202 , low frequency oscillator  204 , modules  210 ,  220  and  230  may refer to the above description and are omitted herein for brevity. The high frequency oscillator  202  is disabled by a disable signal #dis sent from a disablement unit  209  coupled to the first module  210 , second module  220  and third module  230 . When one of the first module  210 , second module  220  and third module  230  switches to idle mode, a corresponding one of request signals #dis 1 , #dis 2  or #dis 3  is delivered to the disablement unit  209 . The disable signal #dis is asserted if all of request signals #dis 1 , #dis 2  and #dis 3  are asserted, and the high frequency oscillator  202  is disabled to stop generation of the first high frequency signal #HCLK 1 , reducing the total power consumption of the communication system  200 . Conversely, if not all of request signals #dis 1 , #dis 2  and #dis 3  is asserted, the disable signal #dis is not sent to disable the high frequency oscillator  202 , and the high frequency oscillator  202  may continue to work. 
       FIG. 11  shows an embodiment of the disablement unit  209  as shown in  FIG. 10   a  or  10   b . The disablement unit  209  may contain at least a buffer  1120  storing a look-up table, and a control unit  1110  selectively asserts the disable signal #dis according to the request signals #dis 1 , #dis 2  and #dis 3  and the stored look-up table. An exemplary look-up table can be shown in  FIG. 12 , in which “1” represents assertion. The buffer  1120  may be implemented in registers, random access memory (RAM), read only memory (ROM), flash memory or others. With reference to the look-up table, the control unit  1110  asserts the disable signal #dis when all of request signals #en 1 , #en 2  and #en 3  are asserted. 
       FIG. 13  shows an embodiment of the disablement unit  209  as shown in  FIG. 10   a  or  10   b . Since the enable signal #dis is asserted when all of request signals #dis 1 , #dis 2  and #dis 3  are asserted, the disablement unit  209  may be implemented by AND gates  1310 ,  1320  and  1330  serially cascaded, each receiving a corresponding disable signal. Based on the serially coupled architecture, the number of AND gates may be extended if more than three modules are implemented in the communication system  200  or  201 .  FIG. 14  shows an embodiment of the disablement unit  209  as shown in  FIG. 10   a  or  10   b . The disablement unit  209  may be implemented by NAND gates  1410 ,  1420  and  1430  serially cascaded with corresponding output inverters  1411 ,  1421 , and  1431 , each receiving a corresponding disable signal. Based on the serially coupled architecture, the number of NAND gates with corresponding output inverters may be extended if more than three modules are implemented in the communication system  200  or  201 .  FIG. 15  shows an embodiment of the disablement unit  209  as shown in  FIG. 10   a  or  10   b . The disablement unit  209  may be implemented by NOR gates  1510 ,  1520  and  1530  serially cascaded with corresponding pairs of input inverters  1511  and  1512 ,  1521  and  1522 , and  1531  and  1532 , each receiving a corresponding disable signal. Based on the serially coupled architecture, the number of NOR gates with corresponding pairs of input inverters may be extended if more than three modules are implemented in the communication system  200  or  201 . Those skilled in the art may implement similar but different logic circuits in the disablement unit  209 . 
       FIG. 16  shows a waveform of the disable signals and the adjustment signals. Disadvantages of the architecture in  FIG. 1 ,  FIG. 10   a  or  10   b  may refer to description of the  FIG. 4 . To solve the disadvantages, the auto frequency controller  208  in  FIG. 10   a  or  10   b  is triggered based on the disable signal #dis sent from the disablement unit  209 , and the voltage status of the adjustment signal #AFC is shown as voltage AFC_C. When all of request signals #dis 1 , #dis 2  and #dis 3  are asserted, the disable signal #dis is asserted, and the voltage AFC_C is sent as the adjustment signal #AFC to maintain the accuracy of first high frequency signal #HCLK 1 . During the intervals I d  where all of request signals #dis 1 , #dis 2  and #dis 3  are asserted, the voltage AFC_C is uncharged to reduce the power consumption. 
       FIG. 17  is a flowchart of the oscillation signal provision method. The low frequency signal #LCLK is generated in step  1701 . The first high frequency signal #HCLK 1  is generated in step  1702  as well. In step  1703 , it is determined whether the disable signal #dis has been asserted. If so, the generation of first high frequency signal #HCLK 1  is ceased in step  1704 , and then, as shown in step  1705 , all of the first module  211 , second module  220  and third module  230  are in idle mode and operate at the low frequency signal #LCLK. Otherwise, in step  1706 , at least one of the first module  210 , second module  220  and third module  230  operating in busy mode utilizes the first high frequency signal #HCLK 1  while the remainder of the first module  210 , second module  220  and third module  230  which operates in idle mode utilizes the low frequency signal #LCLK. 
     While the invention has been described by way of example and in terms of preferred embodiment, it is to be understood that the invention is not limited thereto. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.

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