Data processor and single-chip microcomputer with changing clock frequency and operating voltage

• US 5,778,237 A
• Filed: 12/14/1995
• Issued: 07/07/1998
• Est. Priority Date: 01/10/1995
• Status: Expired due to Term

• Current Assignee: Advanced Processor Technologies LLC (Acacia Research Corporation)
• Original Assignee: Hitachi, Ltd.
• Inventors: Kubo, Masaharu, Inayoshi, Hideo, Narita, Susumu, Kawasaki, Ikuya, Yamamoto, Mitsuyoshi
• Primary Examiner(s): Sheikh, Ayaz R.
• Assistant Examiner(s): PHAN, RAYMOND NGAN
• Application Number:
  US08/572,677
• Time in Patent Office: 936 Days
• Field of Search: 395/750, 395/550, 395/800, 395/306, 395/308, 395/309, 395/750.03, 395/750.04, 395/750.08, 395/555, 395/556, 364/707
• US Class Current: 713/322
• CPC Class Codes: G06F 1/32 Means for saving power
• CPC Class Codes: G06F 1/324 by lowering clock frequency
• CPC Class Codes: G06F 1/3296 by lowering the supply or operating voltage
• CPC Class Codes: Y02D 10/00 Energy efficient computing, e.g. low power processors, power management or thermal management

Abstract

A microcomputer has a clock generator capable of changing the frequency of an output clock signal: and a power circuit capable of changing the level of an operating voltage to be outputted. The frequencies of clock signals and the levels of operating voltages to be individually fed to a plurality of circuit modules can be dynamically changed according to the content of a packaged register. If the content of the register instructs the reduction of the clock signal frequency and the operating voltage in its absolute value, the operating voltage is lowered in its absolute value prior to the change in the clock signal frequency. On the contrary, if the instruction is to increase the frequency of the clock signal and the operating voltage in its absolute value, the clock signal having the increased frequency is outputted prior to the increase of the operating voltage in the absolute value. As a result, it is possible to prevent in advance the malfunctions of the circuit at the time of switching the operation frequency and the operating voltage of the circuit module.

Claims

1. A data processor comprising:

a circuit module operating in synchronism with a clock signal;

a storage circuit storing control data for designating a frequency of the clock signal to be fed to said circuit module and an operating voltage to be fed to said circuit module;

a clock generator outputting a clock signal having a frequency according to the control data of said storage means to said circuit module;

a power circuit outputting an operating voltage having an absolute value according to the control data of said storage means to said circuit module; and

a first control circuit controlling changes in the frequency of the clock signal to be outputted by said clock generator and in the absolute value of the operating voltage to be outputted by said power circuit,

wherein the changes in the frequency of the clock signal and in the absolute value of the operating voltage are designated by changing the control data in the storage circuit, and wherein the operating voltage is prevented from being lowered in its absolute value prior to the lowering of the frequency of the clock signal if the change of the control data is an instruction to reduce the frequency of said clock signal and the absolute value of the operating voltage, and the frequency of the clock signal is prevented from being increased prior to the rise of the absolute value of the operating voltage if the change of the control data is an instruction to increase the clock signal frequency and the absolute value of the operating voltage.

2. A data processor according to claim 1,

wherein said clock generator includes an output gate for stopping the outputting of the clock signal for a predetermined time period in response to the control data from said first control circuit, at a time of change in the frequency of the clock signal to be outputted.

3. A data processor according to claim 1, further comprising:

a second control circuit coupled to the storage circuit and controlling changes in the frequency of the clock signal to be outputted by said clock generator and in the absolute value of the operating voltage to be outputted by said power circuit on the basis of control data before and after the change of the control data in the storage circuit, wherein the second control circuit controls so as to inhibit the changes in the frequency of the clock signal to be outputted by said clock generator and in the absolute value of the operating voltage to be outputted by said power circuit if the control data in the storage circuit designates that the frequency of the clock signal is risen without rising the absolute value of the operating voltage and that the absolute value of the operating voltage is lowered without lowering the frequency of the clock signal.

4. A data processor according to claim 1,

wherein said circuit module includes a plurality of circuit modules,

wherein said storage circuit includes a plurality of storage regions each of which reloadably stores control data corresponding to each of said circuit modules,

wherein said clock generator includes a selector selecting an clock signal to be fed to a circuit module in accordance with the corresponding control data of said storage regions in said storage circuit, and

wherein said power circuit includes a selector selecting an operating voltage to be fed to a circuit module in accordance with the corresponding control data of said storage regions in said storage circuit.

5. A data processor according to claim 4,

wherein one of said circuit modules is a central processing unit,

wherein one of said circuit modules is a circuit module whose operation is controlled by said central processing unit, and

wherein said circuit modules are included in a single-chip microcomputer formed on one semiconductor substrate.

6. A data processor according to claim 4,

wherein said circuit modules, said storage circuit, said first control circuit and said second control circuit are included in a semiconductor chip, and

wherein said clock generator and said power circuit are disposed outside of said semiconductor chip.

7. A data processor according to claim 4,

wherein first one of said circuit modules is a central processing unit,

wherein second one of said circuit modules is a circuit module whose operation is controlled by said central processing unit,

wherein said central processing unit, said second one of the circuit modules, said storage circuit, said first control circuit and said second control circuit are included in a semiconductor chip, and

wherein one of the circuit modules excepting said central processing unit and the second one of the circuit modules, said clock generator and said power circuit are disposed outside of said semiconductor chip.

8. A data processor according to claim 4,

wherein said storage circuit is a register to be accessed by said central processing unit.

9. A single-chip microcomputer comprising:

a central processing unit operating in accordance with a clock signal;

an input/output circuit;

a peripheral circuit operating in accordance with a clock signal;

a bus controller operating in accordance with a clock signal and controlling an interface with an external bus to be disposed outside of said single-chip microcomputer, through said input/output circuit;

a first internal bus to which is coupled said central processing unit;

a second internal bus, to which is coupled said bus controller and to which is coupled said central processing unit while interfacing with the external bus through said input/output circuit;

a third internal bus to which is coupled said peripheral circuit;

a clock generator outputting a first clock signal for the central processing unit coupled to said first internal bus, a second clock signal for the bus controller coupled to said second internal bus, and a third clock signal for the peripheral circuit coupled to said third internal bus; and

a clock controller coupled to said first internal bus and to the clock generator, and changing a frequency of the first clock signal without changing a frequency of the second clock signal in accordance with control data set by said central processing unit.

10. A single-chip microcomputer according to claim 9, further comprising:

an output terminal an external clock signal to be fed to a circuit module to be coupled to said external bus,

wherein said clock controller outputs a clock signal having a frequency equal to that of said external clock signal, as said second clock signal.

11. A single-chip microcomputer according to claim 10, further comprising:

a cache memory unit coupled to said first internal bus and said second internal bus for effecting the interfaces between said first internal bus and said second internal bus.

12. A data processor, as constructed into a single-chip microcomputer, comprising:

a first internal bus to which is coupled a central processing unit;

a second internal bus interfacing through an input/output circuit with an external bus disposed outside of said data processor and to which is coupled a bus controller for controlling the interface with said external bus;

a third internal bus to which is coupled a predetermined peripheral circuit;

a clock pulse generator for outputting a first clock signal for a circuit module coupled to said first internal bus, a second clock signal for a circuit module coupled to said second internal bus, and a third clock signal for a circuit module coupled to said third internal bus; and

a clock controller for controlling the frequencies of said first to third clock signals individually,

wherein said clock pulse generator includes;

first frequency changing means connected with a first connection terminal adapted to be coupled to a clock generator disposed outside;

second frequency changing means coupled to a second connection terminal adapted to be coupled to said clock generator;

select means for selecting one of said first and second frequency changing means;

third frequency changing means for making said first to third clock signal frequencies individually changeable in response to the clock signal selected by said select means; and

a clock signal output path for outputting the clock signal, which is outputted from said first frequency changing means, as an external clock signal, and

wherein said clock controller includes a clock control register coupled to an external clock mode terminal and having control data set by said central processing unit for especially designating the frequency changing ratios of said first and third clock signals by said third frequency changing means and for designating the frequency changing ratio by said second frequency changing means, wherein said clock controller decides the frequency changing ratio by said first frequency changing means in accordance with the status of said external clock mode terminal, to select a first state, in which said third frequency changing means is controlled so that a clock signal can be transmitted from said first connection terminal to the input of said third frequency changing means and so that said second clock signal frequency may be equal to the frequency of the clock signal outputted from said first frequency changing means, and a second state, in which a clock signal can be transmitted from said second connection terminal to the input of said third frequency changing means, wherein said clock controller controls the frequency changing ratio by said second frequency changing means and the frequency changing ratios of said first and third clock signals by said third frequency changing means variably according to the control data set in said clock control register, and controls the frequency changing ratio of said second clock signal by said third frequency changing means in said second state designated at said clock mode terminal in accordance with the control data set in said clock control register, so that the frequency of said second clock signal may be equal to the frequency of the clock signal fed from said second connection terminal.

13. A data processor according to claim 12, further comprising:

connection means for connecting the output of said first frequency changing means to the input of said second frequency changing means in said first state designated at said clock mode terminal.

14. A data processor according to claim 13,

wherein said clock signal output path is coupled to said second connection terminal.

15. A data processor according to claim 14,

wherein said first frequency changing means includes:

a frequency diver and a phase locked loop circuit for selecting either of the clock signal coming from an oscillator having its oscillation element attached to said first connection terminal and adapted to oscillate or the clock signal fed directly from said first connection terminal and for receiving the selected clock signals individually; and

select means for outputting either of the outputs as a fundamental clock signal, and

wherein said second frequency changing means includes a phase locked loop circuit.

16. A single-chip microcomputer comprising:

a central processing unit;

a circuit module operating in synchronism with a clock signal;

a register stores control data for designating a frequency of the clock signal to be fed to said circuit module and an operating voltage to be fed to said circuit module;

a clock generator outputting a clock signal having a frequency according to the control data of said register to said circuit module;

a power circuit outputting an operating voltage having an absolute value according to the control data of said register to said circuit module; and

a first control unit controlling changes in the frequency of the clock signals to be outputted by said clock generator and in the absolute value of the operating voltage to be outputted by said power circuit,

wherein the changes in the frequency of the clock signal and in the absolute value of the operating voltage are designated by changing the control data in the storage circuit, and wherein the operating voltage is prevented from being lowered in its absolute value prior to the lowering of the frequency of the clock signal if the change of the control data is an instruction to reduce the frequency of said clock signal and the absolute value of the operating voltage, and the frequency of the clock signal is prevented from being increased prior to the rise of the absolute value of the operating voltage if the change of the control data is an instruction to increase the clock signal frequency and the absolute value of the operating voltage, in which the operating voltage is lowered in its absolute value prior to the change in the frequency, when it detects an instruction to reduce the frequency of said clock signal and the operating voltage in its absolute value, and by blocking the state, in which the clock signal having its frequency increased is outputted prior to the rise of the operating voltage in its absolute value, when it detects an instruction to increase the clock signal frequency and the operating voltage in its absolute value!, wherein the changes in the frequency of the clock signal and in the absolute value of the operating voltage are designated by changing the control data in the storage circuit, and wherein the first control circuit controls so as to prevent the absolute value of the operating voltage from being lowered prior to a lower in the frequency of the clock signal if the change of the control data instructs both of a lower in the frequency of the clock signal and a lower in the absolute value of the operating voltage, and so as to prevent the frequency of the clock signal from being risen prior to a rise in the absolute value of the operating voltage if the change of the control data instructs both of a rise in the frequency of the clock signal and a rise in the absolute value of the operating voltage.

17. A data processor according to claim 16,

wherein said clock generator includes an output gate for stopping the outputting of the clock signal for a predetermined time period in response to the control data from said first control circuit, at a time of change in the frequency of the clock signal to be outputted.

18. A data processor according to claim 16, further comprising:

second control circuit coupled to the register and controlling changes in the frequency of the clock signal to be outputted by said clock generator and in the absolute value of the operating voltage to be outputted by said power circuit on the basis of control data before and after the change of the control data in the register, wherein the second control circuit controls so as to inhibit the changes in the frequency of the clock signal to be outputted by said clock generator and in the absolute value of the operating voltage to be outputted by said power circuit if the control data in the register designates that the frequency of the clock signal is risen without rising the absolute value of the operating voltage and that the absolute value of the operating voltage is lowered without lowering the frequency of the clock signal.

19. A data processor according to claim 16, wherein said circuit module includes a plurality of circuit modules,

wherein said register includes a plurality of storage regions each of which reloadably stores control data corresponding to each of said circuit modules,

wherein said clock generator includes a selector selecting a clock signal to be fed to each of the circuit modules in accordance with the control data of a corresponding storage region in the storage regions in said register, and

wherein said power circuit includes a selector selecting an operating voltage to be fed to a circuit module in the circuit modules in accordance with control data of a corresponding storage region in the storage regions in said register.

20. A data processor according to claim 19,

wherein said register is a register to be accessed to by said central processing unit.

21. A single-chip microcomputer comprising:

a central processing unit operating in accordance with a clock signal;

an input/output circuit;

a peripheral circuit operating in accordance with a clock signal;

a bus controller operating in accordance with a clock signal and controlling an interface with an external bus to be disposed outside of said single-chip microcomputer, through said input/output circuit;

a clock generator outputting a first clock signal for the central processing, a second clock signal for the bus controller, and a third clock signal for the peripheral circuit; and

a clock controller coupled to the clock generator, and changing a frequency of the first clock signal without changing a frequency of the second clock.

22. A single-chip microcomputer according to claim 21,

wherein said peripheral circuit includes a timer circuit and a serial interface circuit.

23. A single-chip microcomputer according to claim 22, further comprising:

a first internal bus coupled to the central processing unit, a cache memory unit and to an address translation table;

a second internal bus coupled to the input/output circuit and to the bus controller; and

a third bus coupled to the timer circuit and to the serial interface circuit.