Abstract:
A DLL circuit includes an input circuit generating a synchronization reference signal, a first delay unit delaying the synchronization reference signal to generate a plurality of delayed synchronization reference signals and selecting one of the delayed synchronization reference signals, a timing offset circuit adjusting a synchronization position of the delayed synchronization reference signal to generate a signal to be synchronized, a phase comparison circuit comparing phase of the synchronization reference signal with that of the signal to be synchronized, a first control circuit selecting an output signal of the first delay unit, a second delay unit delaying the synchronization reference signal or the signal to be synchronized to generate a plurality of delayed signals, a configuration information memory storing configuration information, and a second control circuit selecting an output signal of the second delay unit if the comparison result of the phase comparison circuit is within a predetermined range.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2008-221064, filed on Aug. 29, 2008; the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to a DLL (Delay Locked Loop) circuit and, more particularly, to a DLL circuit having the function of reducing intensity of electromagnetic radiation noise. 
     An LSI (Large Scale Integration) mounted on an electronic device emits electromagnetic waves in response to power consumption and to operation frequency. Electromagnetic waves exert an adverse influence such as electromagnetic radiation noise on an entire electronic device. The main cause of the electromagnetic radiation noise is electromagnetic waves generated from a DLL circuit in the LSI and other circuits using an output signal (DLL output signal) of the DLL circuit. In particular, strong electromagnetic waves are generated from the other circuits using the DLL output signal. 
     On the other hand, as electronic devices are sophisticated and the integration technique has improved in recent years, the power consumption, operation frequency, packaging density, and the number of LSIs mounted on an electronic device have been increasing. As a result, the intensity of electromagnetic waves (electromagnetic radiation intensity) emitted from the LSI increases, and the influence of electromagnetic radiation noise exerted on the electronic device is becoming unignorable. 
     An ordinary LSI has a DLL circuit. When the DLL circuit is in a locked state (that is, the DLL circuit and the LSI having the DLL circuit are in an operating state), the frequency of a DLL output signal of the DLL circuit has a constant value (DLL locked frequency). As a result, the electromagnetic radiation intensity at the DLL lock frequency becomes very high. 
     A DLL circuit suppressing minimum delay time (minimum slew rate) of delay time which can be adjusted in a wide range is known (Japanese Patent Application Laid-open Publication No. 2004-260663). However, the Japanese Patent Application Laid-open Publication No. 2004-260663 does not disclose means for reducing the electromagnetic radiation noise caused by the DLL circuit. 
     Therefore, the electromagnetic radiation intensity of the conventional DLL circuit and that of an LSI having the DLL circuit is high. There is a problem such that an electronic device having the LSI is adversely influenced by the electromagnetic radiation noise. 
     Furthermore, a peak of the electromagnetic radiation intensity of the conventional DLL circuit and that of the LSI having the DLL circuit appears at particular operation frequency. Since this peak is very high, the electronic device having this LSI is adversely influenced by the electromagnetic radiation generated from this LSI. Therefore, the LSI having DLL circuit is required to have a function to prevent EMI (Electro Magnetic Interference). 
     However, the function to prevent EMI depends on configurations of the electronic device. Therefore, if the function to prevent EMI having scalability, for example the function for shifting distribution of frequency and for controlling shape of distribution of frequency, is not used, a various restrictions is imposed users which use the LSI. 
     SUMMARY OF THE INVENTION 
     According to the aspect of the present invention, there is provided a DLL circuit comprising: 
     an input circuit configured to generate a synchronization reference signal on the basis of an input signal; 
     a first delay module configured to delay the synchronization reference signal to generate a plurality of delayed synchronization reference signals and to select one of the delayed synchronization reference signals; 
     a timing offset circuit configured to adjust a synchronization position of the delayed synchronization reference signal selected by the first delay module to generate a signal to be synchronized; 
     a phase comparison circuit configured to compare phase of the synchronization reference signal with that of the signal to be synchronized; 
     a first control circuit configured to select an output signal of the first delay module on the basis of a comparison result of the phase comparison circuit; 
     a second delay module configured to delay the synchronization reference signal or the signal to be synchronized to generate a plurality of delayed signals; 
     a configuration information memory configured to store configuration information for shifting distribution of frequency; and 
     a second control circuit configured to select an output signal of the second delay module based on the configuration information stored in the configuration information memory in the case where the comparison result of the phase comparison circuit is within a predetermined range. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a circuit diagram showing the configuration of a DLL circuit of the first embodiment of the invention. 
         FIG. 2  is a flowchart showing the procedure of the DLL circuit in the selection delayed synchronization target signal generation process of the first embodiment of the present invention. 
         FIG. 3  is a graph showing distribution of frequency of the intensity of electromagnetic waves of the first invention of the present invention. 
         FIGS. 4 and 5  are circuit diagrams showing the configuration of a DLL circuit of the modifications of the first embodiment of the invention. 
         FIG. 6  is a circuit diagram showing the configuration of a DLL circuit of the second embodiment of the invention. 
         FIG. 7  is a flowchart showing the procedure of the DLL circuit in the selection delayed synchronization target signal generation process of the second embodiment of the present invention. 
         FIG. 8  is a graph showing distribution of frequency of the intensity of electromagnetic waves of the second invention of the present invention. 
         FIGS. 9 to 11  are circuit diagrams showing the configuration of a DLL circuit of the modifications of the second embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present invention will be described hereinbelow with reference to the drawings. The following embodiments are aspects of the present invention and do not limit the scope of the invention. 
     Embodiment 1 
     A first embodiment of the present invention will be described. The first embodiment of the present invention is an example of DLL circuit having a selection signal generation circuit configured to generate a selection signal based on configuration information. 
     Configuration of a DLL circuit of the first embodiment of the present invention will be described.  FIG. 1  is a circuit diagram showing the configuration of a DLL circuit of the first embodiment of the invention. 
     As shown in  FIG. 1 , the DLL circuit of the first embodiment of the present invention has an input circuit  101 , a first delay module  102 , a timing offset circuit  103 , a second delay module  104 , a phase comparison circuit  105 , a first control circuit  106 , a second control circuit  107 , and a configuration information memory  108 . 
     As shown in  FIG. 1 , the input circuit  101  is connected to external circuits (not shown), a delay line  1021  (describe later) of the first delay module  102 , and the phase comparison circuit  105 . The input circuit  101  is configured to receive a DLL input signal ( 201 ), to generate a “synchronization reference signal ( 202 )” which is a basis of synchronization from the DLL input signal ( 201 ), and to output the synchronization reference signal ( 202 ) to the first delay module  102  and the phase comparison circuit  105 . 
     As shown in  FIG. 1 , the first delay module  102  has the delay line  1021  and selection circuit  1022 . The delay line  1021  and the selection circuit  1022  are serially connected via a plurality of signal lines. 
     As shown in  FIG. 1 , the delay line  1021  is connected to the input circuit  101  and the selection circuit  1022 . The delay line  1021  is configured to receive the “synchronization reference signal ( 202 )” output from the input circuit  101 , and to delay the signal only by predetermined delay time, thereby generating a plurality of “delayed synchronization reference signals ( 203 )”. 
     As shown in  FIG. 1 , the selection circuit  1022  is connected to the external circuits, the delay line  1021 , the timing offset circuit  103 , and the first control circuit  106 . The selection circuit  1022  is configured to select one of the plurality of “delayed synchronization reference signals ( 203 )” output from the delay line  1021  in accordance with a “control signal ( 207 ) (describe later)” output from the first control circuit  106 . The selection circuit  1022  is configured to output selected one to the external circuit as a “DLL output signal ( 204 )”. 
     As shown in  FIG. 1 , the timing offset circuit  103  is connected to the external circuit, the selection circuit  1022  of the first delay module  102 , and the second delay module  104 . The timing offset circuit  103  is configured to receive the “DLL output signal ( 204 )” output from the selection circuit  1022 , to adjust a synchronization position, thereby generating a “signal ( 205 ) to be synchronized”, and to output the signal ( 205 ) to be synchronized to the second delay module  104 . 
     As shown in  FIG. 1 , the second delay module  104  has five delay circuits  1041  to  1045  and a phase comparison target selection circuit  1046 . The delay circuits  1041  to  1045  are serially connected to the phase comparison target selection circuit  1046 . 
     As shown in  FIG. 1 , the delay circuits  1041  to  1045  are connected to the timing offset circuit  103  and the phase comparison target selection circuit  1046 . Each delay circuits  1041  to  1045  has different delay time (D 1  to D 5 ). For example, in the case where the operation frequency of a processor mounted on the LSI is 1 GHz, D 1 =20 ps (delay time of the delay circuit  1041 ), D 2 =40 ps (delay time of the delay circuit  1042 ), D 3 =60 ps (delay time of the delay circuit  1043 ), D 4 =80 ps (delay time of the delay circuit  1044 ), and D 5 =100 ps (delay time of the delay circuit  1045 ). Each delay circuits  1041  to  1045  is configured to receive the signal ( 205 ) to be synchronized from the timing offset circuit  103 , to delay the signal ( 205 ) to be synchronized only by predetermined delay time, thereby generating a plurality of “delayed synchronization target signals ( 2081  to  2085 ), and to output the delayed signals to the phase comparison target selection circuit  1046 . The number of the delay circuits  1041  to  1045  may be two or more. 
     As shown in  FIG. 1 , the phase comparison target selection circuit  1046  is connected to the delay circuits  1041  to  1045  and the phase comparison circuit  105 . The phase comparison target selection circuit  1046  is configured to select one a plurality of the “delayed synchronization target signals ( 2081  to  2085 )” output from the delay circuits  1041  to  1045  in accordance with a “selection signal ( 214 )” output from a selection signal generation circuit  1073  (described later), and to output the selected one to the phase comparison circuit  105  as a selection delayed synchronization target signal ( 209 ) which is an output signal of the second delay module  104 . 
     As shown in  FIG. 1 , the phase comparison circuit  105  is connected to the input circuit  101 , the phase comparison target selection circuit  1046  of the second delay module  104 , and the first control circuit  106 . The phase comparison circuit  105  is configured to receive the “synchronization reference signal ( 202 )” output from the input circuit  101  and the “selection delayed synchronization target signal ( 209 )” output from the phase comparison target selection circuit  1046 , to compare the phases of both signals, and to output a “comparison result ( 206 )” to the first control circuit  106 . 
     As shown in  FIG. 1 , the first control circuit  106  is connected to the selection circuit  1022  of the first delay module  102 , the phase comparison circuit  105 , and a cycle counter  1071  (described later) of the second control circuit  107 . The first control circuit  106  is configured to receive the “comparison result ( 206 )” output from the phase comparison circuit  105 , to generate the “control signal ( 207 )” for controlling the selection circuit  1022  in accordance with the “comparison result ( 206 )”, and to output the “control signal ( 207 )” to the selection circuit  1022 . The first control circuit  106  also is configured to generate a “cycle counter enable signal ( 210 )” for setting the cycle counter  1071  into an enable state in accordance with the “comparison result ( 206 )”, and to output the cycle counter enable signal ( 210 ) to the cycle counter  1071 . When the “cycle counter enable signal ( 210 )” is generated by the first control circuit  106 , the DLL circuit enters a so-called “locked state”. 
     As shown in  FIG. 1 , the second control circuit  107  has the cycle counter  1071 , a comparison circuit  1072 , and a selection signal generating circuit  1073 . The second control circuit  107  is connected to the configuration information memory  108 . 
     As shown in  FIG. 1 , the cycle counter  1071  is connected to the first control circuit  106  and the comparison circuit  1072 . The cycle counter  1071  is configured to start counting the number of cycles in response to the “cycle counter enable signal ( 210 )” output from the first control circuit  106 , and to output a “cycle count value ( 212 )” to the comparison circuit  1072 . The cycle counter  1071  is configured to reset the cycle count value when the “comparison result ( 212 )” of the comparison circuit  1072  indicates a “match”. 
     As shown in  FIG. 1 , the comparison circuit  1072  is connected to the cycle counter  1071  and the selection signal generating circuit  1073 . The comparison circuit  1072  is configured to compare the “cycle count value ( 212 )” output from the cycle counter  1071  with a predetermined “delay circuit switching cycle set value ( 211 )” and to output a “comparison result ( 213 )” to the selection signal generating circuit  1073 . 
     As shown in  FIG. 1 , the selection signal generating circuit  1073  is connected to the comparison circuit  1072  and the phase comparison target selection circuit  1046 . The selection signal generating circuit  1073  is configured to generate a “selection signal ( 214 )” for controlling the phase comparison target selection circuit  1046  in accordance with the “comparison result ( 213 )” output from the comparison circuit  1072 , and to output the “selection signal ( 214 )” to the phase comparison target selection circuit  1046 . The selection signal generating circuit  1073  generates the “selection signal ( 214 )” so as to select the “delayed synchronization target signal ( 2083 )” output from a delay circuit having the longest delay time next to that of the delay circuit selected just before (for example, the delay circuit  1044  in the case where the delay circuit  1043  is selected just before). On the other hands, when the DLL circuit is in the unlocked state, the selection signal generating circuit  1073  generates the “selection signal ( 214 )” so as to select the “delayed synchronization target signal ( 2083 )” shown in unlocked output signal information  108   a . The selection signal generating circuit  1073  may generate the “selection signal ( 214 )” so as to select a “delayed synchronization target signal” output from a delay circuit having the shortest delay time next to that of a delay circuit selected just before. In the case where the delay circuit selected just before is a delay circuit having the shortest delay time (or the longest delay time), the selection signal generating circuit  1073  may generate the “selection signal ( 214 )” so as to select a “delayed synchronization target signal” output from the delay circuit having the longest delay time (or the shortest delay time). 
     As shown in  FIG. 1 , the configuration information memory  108  is connected to the second control circuit  107 . The configuration information memory  108  is configured to store the unlocked output signal information  108   a , on/off information  108   c , and suspension period information  108   d . The unlocked output signal information  108   a  is indicative of the output signal of the second delay module  104  to be selected in the case of the unlocked state (that is the DLL circuit is not in the locked state). The on/off information  108   c  is indicative of on/off of the second control circuit  107 . The suspension period information  108   d  indicative of a time range of on/off of the second control circuit  107 . Setting the unlocked output signal information  108   a , on/off information  108   c , and suspension period information  108   d  is performed by software executed in the LSI having the DLL circuit of the first embodiment of the present invention or pins (not shown) of the configuration information memory  108 . 
     Process of the DLL circuit of the first embodiment of the present invention will be described.  FIG. 2  is a flowchart showing the procedure of the DLL circuit in the selection delayed synchronization target signal generation process of the first embodiment of the present invention.  FIG. 3  is a graph showing distribution of frequency of the intensity of electromagnetic waves of the first invention of the present invention. 
     First, as shown in  FIG. 2 , when the DLL circuit is in the unlocked state (S 201 —NO), the selection signal generating circuit  1073  refers the unlocked output signal information  108   a  stored in the configuration information memory  108 , generate the selection signal ( 214 ) so as to select one of the delayed synchronization target signals ( 2081  to  2085 ) indicated in the unlocked output information, and outputs the selection signal ( 214 ) to the phase comparison target selection circuit  1046  (S 202 ). At this time, the phase comparison target selection circuit  1046  selects one of the delayed synchronization target signals ( 2081  to  2085 ), and outputs the selected signal to the phase comparison circuit  105 . 
     On the other hand, when the DLL circuit is in the locked state (S 201 —YES), the first control circuit  106  generates the “cycle counter enable signal ( 210 )” (S 203 ). Next, the cycle counter  107  starts counting the cycles (S 204 ). Next, in the case where the “comparison result ( 213 )” output from the comparison circuit  1072  shows a match (S 205 —YES), the selection signal generation circuit  1073  generates the “selection signal ( 214 )” (S 206 ). Next, the cycle counter  107  resets the cycle count value (S 207 ). Next, the phase comparison target selection circuit  1046  selects the selection delayed synchronization target signal ( 209 ) output from a delay circuit different from the delay circuit selected just before (for example, a delay circuit having the longest delay time next to that of the delay circuit selected just before) (S 208 ). 
     The steps S 201  to S 208  are repeated until an end signal is detected (S 209 —NO). 
     On the other hand, when the end signal is detected after the step S 202  or S 208  (S 209 —YES), the selection delayed synchronization target signal generation process of the first embodiment of the present invention is completed. The end signal is detected in the case where the LSI shifts to a sleep state, is reset, or shifts to a power saving mode. In the power saving mode, the DLL circuit of the first embodiment of the present invention stops the operation of the timing offset circuit  103 , the second delay module  104 , the phase comparison circuit  105 , and the second control circuit  107 . The first delay module  102  outputs the “DLL output signal ( 204 )” at a constant frequency. 
     In the first embodiment of the present invention, in the case where the DLL circuit is in the unlocked state, the output signal of the second delay module  104  is decided based on the unlocked output signal information  108   a  stored in the configuration information memory  108 . Therefore, users can optionally change the distribution of frequency of the intensity of electromagnetic waves by setting the optional unlocked output signal information  108   a . For example, as shown in  FIG. 3(A) , users can set the unlocked output signal information  108   a  so that a top of the peak of the intensity of electromagnetic waves appears at the target operation frequency. As shown in  FIG. 3(B) , users can set the unlocked output signal information  108   a  so that a bottom of the peak of the intensity of electromagnetic waves appears at the target operation frequency. As shown in  FIG. 3(C) , users can set the unlocked output signal information  108   a  so that the target operation frequency is not matched with a center of the intensity of electromagnetic waves. 
     In the modification of the first embodiment of the present invention, the second control circuit  107  may operate only while the on/off information  108   c  stored in the configuration information memory  108  is indicative of “on”. In this case, the process shown in  FIG. 2  is executed only while the on/off information  108   c  stored in the configuration information memory  108  is indicative of “on”. In this case, the DLL circuit of the modification of the first embodiment of the present invention can be applied to the LSI that needs the second control circuit  107 . As a result, production cost is reduced. 
     In another modification of the first embodiment of the present invention, the cycle counter  1071  may suspend to count only for the time range indicated in the suspension period information  108   d  stored in the configuration information memory  108 . In this case, the phase comparison target selection circuit  1046  continuously selects the selection delayed synchronization target signal ( 209 ) which is selected just before. In this case, the DLL circuit of another modification of the first embodiment of the present invention can be applied to the LSI that needs jitter reduction for high accuracy and high speed transfer. 
     In another modification of the first embodiment of the present invention, as shown in  FIG. 4 , between the input circuit  101 , the first delay module  102 , and the phase comparison circuit  105 , the second delay module  104  which is configured to delay the synchronization reference signal may be located, the second control circuit  107  may be connected to the second delay module  104 , and the configuration information memory  108  may be connected to the second control circuit  107 . 
     In another modification of the first embodiment of the present invention, as shown in  FIG. 5 , the second delay module  104  which is configured to delay the DLL output signal may be located at the output side of the DLL circuit, the second delay module  104  may be connected to the second control circuit  107 , and the configuration information memory  108  may be connected to the second control circuit  107 . 
     According to the first embodiment of the present invention, the second control circuit  107  operates based on the configuration information  108   a ,  108   c , or  108   d  stored in the configuration information memory  108 . Therefore, the distribution of frequency of the intensity of electromagnetic waves can be shifted depending on the use or the operation situation of the LSI. 
     Embodiment 2 
     A second embodiment of the present invention will be described. In the second embodiment of the present invention, an example of the DLL circuit having the switching cycle selection circuit which is configured to select one corresponding to the selected delay circuit of a plurality of switching cycle set values. The description similar to that of the first embodiment of the present invention will not be repeated. 
     Configuration of a DLL circuit of the second embodiment of the present invention will be described.  FIG. 6  is a circuit diagram showing the configuration of a DLL circuit of the second embodiment of the invention. 
     As shown in  FIG. 6 , the DLL circuit of the second embodiment of the present invention has the input circuit  101 , a first delay module  102 , the timing offset circuit  103 , the second delay module  104 , the phase comparison circuit  105 , the first control circuit  106 , the second control circuit  107 , the configuration information memory  108 , and a switching cycle selection circuit  109 . The input circuit  101 , the first delay module  102 , the timing offset circuit  103 , the second delay module  104 , the phase comparison circuit  105 , and the first control circuit  106  are same to them of the first embodiment of the present invention. 
     As shown in  FIG. 6 , the second control circuit  107  has a cycle counter  1071 , a comparison circuit  1072 , and a selection signal generating circuit  1073 . The cycle counter  1071  is same to one of the first embodiment of the present invention. 
     As shown in  FIG. 6 , the comparison circuit  1072  is connected to the cycle counter  1071 , the selection signal generating circuit  1073 , and the switching cycle selection circuit  109 . The comparison circuit  1072  is configured to compare the “cycle count value ( 212 )” output from the cycle counter  1071  with selected one of switching cycle set values  108   e  to  108   i  (described later) and to output a “comparison result ( 213 )” to the selection signal generating circuit  1073 . 
     As shown in  FIG. 6 , the selection signal generating circuit  1073  is connected to the comparison circuit  1072 , the phase comparison target selection circuit  1046 , and the switching cycle selection circuit  109 . The selection signal generating circuit  1073  is configured to generate a “selection signal ( 214 )” for controlling the phase comparison target selection circuit  1046  in accordance with the “comparison result ( 213 )” output from the comparison circuit  1072 , and to output the “selection signal ( 214 )” to the phase comparison target selection circuit  1046  and the switching cycle selection circuit  109 . 
     As shown in  FIG. 6 , the configuration information memory  108  is connected to the switching cycle selection circuit  109 . The configuration information memory  108  is configured to store a plurality of switching cycle set values  108   e  to  108   i . Each switching cycle set values  108   e  to  108   i  is configuration information corresponding to each delay circuits  1041  to  1045  of the second delay module  104  and is indicative of the switching cycle of the comparison circuit  1072  of the second control circuit  107 . In other words, the each switching cycle set values  108   e  to  108   i  is indicative of a time range for selecting the output signal of the second delay module  104 . The switching cycle set values  108   e  to  108   i  are set using software executed on the LSI having the DLL circuit of the second embodiment of the present invention or by pins (not shown) of the configuration information memory  108 . 
     As shown in  FIG. 6 , the switching cycle selection circuit  109  is connected to the comparison circuit  1072  and the selection signal generating circuit  1073  of the second control circuit  107 , and the configuration information memory  108 . The switching cycle selection circuit  109  is configured to read out one corresponding to the selection delayed synchronization target signal ( 209 ) of a plurality of switching cycle set values  108   e  to  108   i  from the configuration information memory  108 , and to output one read out to the comparison circuit  1072 . 
     Process of the DLL circuit of the second embodiment of the present invention will be described.  FIG. 7  is a flowchart showing the procedure of the DLL circuit in the selection delayed synchronization target signal generation process of the second embodiment of the present invention.  FIG. 8  is a graph showing distribution of frequency of the intensity of electromagnetic waves of the second invention of the present invention. 
     First, as shown in  FIG. 7 , when the DLL circuit is in the unlocked state (S 701 —NO), the phase comparison target selection circuit  1046  select a standard delayed synchronization target signal”, for example delayed synchronization target signal ( 2083 )”, output from a standard delay circuit, for example the delay circuit  1043  (S 702 ). 
     On the other hand, when the DLL circuit is in the locked state (S 701 —YES), the first control circuit  106  generates the “cycle counter enable signal ( 210 )” (S 703 ). Next, the cycle counter  107  starts counting the cycles (S 704 ). Next, in the case where the cycle count value ( 212 ) matches one corresponding to the selection delayed synchronization target signal ( 209 ) of a plurality of the switching cycle set values  108   e  to  108   i  (the “comparison result ( 213 )” output from the comparison circuit  1072  shows a match) (S 705 —YES), the selection signal generation circuit  1073  generates the “selection signal ( 214 )” (S 706 ). Next, the cycle counter  107  resets the cycle count value (S 707 ). Next, the phase comparison target selection circuit  1046  selects the selection delayed synchronization target signal ( 209 ) output from a delay circuit different from the delay circuit selected just before (for example, a delay circuit having the longest delay time next to that of the delay circuit selected just before) (S 708 ). 
     The steps S 701  to S 708  are repeated until an end signal is detected (S 709 —NO). 
     On the other hand, when the end signal is detected after the step S 702  or S 708  (S 709 —YES), the selection delayed synchronization target signal generation process of the second embodiment of the present invention is completed. The end signal is detected in the case where the LSI shifts to a sleep state, is reset, or shifts to a power saving mode. In the power saving mode, the DLL circuit of the second embodiment of the present invention stops the operation of the timing offset circuit  103 , the second delay module  104 , the phase comparison circuit  105 , and the second control circuit  107 . The first delay module  102  outputs the “DLL output signal ( 204 )” at a constant frequency. 
     In the second embodiment of the present invention, the output signal of the second delay module  104  in the locked state is defined based on the switching cycle set values  108   e  to  108   i  stored in the configuration information memory  108 . Therefore, users can optionally change the distribution of frequency of the intensity of electromagnetic waves by setting the switching cycle set values  108   e  to  108   i . For example, as shown in  FIG. 8(A) , users can change the distribution of frequency of the intensity of electromagnetic waves so that the peak of the intensity of electromagnetic waves appears around the target operation frequency. As shown in  FIG. 8(B) , users can change the distribution of frequency of the intensity of electromagnetic waves so that the peak of the intensity of electromagnetic waves appears at a lower frequency than the target operation frequency, and so that the intensity of electromagnetic waves becomes lower as the frequency becomes higher. 
     In the modification of the second embodiment of the present invention, as shown in  FIG. 9 , the configuration information memory  108  may store the unlocked output signal information  108   a , on/off information  108   c , and suspension period information  108   d . In this case, the configuration information memory  108  is also connected to the second control circuit  107 . The step of S 702  in  FIG. 7  is the same as the step of S 202  in  FIG. 2 . 
     In another modification of the second embodiment of the present invention, as shown in  FIG. 10 , between the input circuit  101 , the first delay module  102 , and the phase comparison circuit  105 , the second delay module  104  which is configured to delay the synchronization reference signal may be located, the second control circuit  107  may be connected to the second delay module  104 , the second control circuit  107  may be connected to the switching cycle selection circuit  109 , and the switching cycle selection circuit  109  may be connected to the configuration information memory  108 . 
     In another modification of the second embodiment of the present invention, as shown in  FIG. 11 , the second delay module  104  which is configured to delay the DLL output signal may be located at the output side of the DLL circuit, the second control circuit  107  may be connected to the switching cycle selection circuit  109 , and the configuration information memory  108  may be connected to the switching cycle selection circuit  109 . 
     According to the second embodiment of the present invention, the switching cycle selection circuit  109  selects one of the switching cycle set values  108   e  to  108   i  stored in the configuration information memory  108 , and outputs the selected one to the comparison circuit  1072 . Therefore, the form of the distribution of frequency of the intensity of electromagnetic waves can be controlled depending on the use or the operation situation of the LSI. 
     The various modules of the systems described herein can be implemented as software applications, hardware and/or software modules, and/or components on one or more computers, such as servers and/or through transistors or other integrated circuits. While the various modules are illustrated separately, they may share some or all of the same underlying logic or code.