Logic LSI

• US 5,585,750 A
• Filed: 06/07/1995
• Issued: 12/17/1996
• Est. Priority Date: 06/07/1994
• Status: Expired due to Term

• Current Assignee: Renesas Electronics Corporation
• Original Assignee: Hitachi, Ltd.
• Inventors: Ohba, Shinya, Narita, Susumu, Noguchi, Kouki, Nishioka, Kiyokazu
• Primary Examiner(s): Callahan, Timothy P.
• Assistant Examiner(s): Lam, T.
• Application Number:
  US08/478,403
• Time in Patent Office: 559 Days
• Field of Search: 327/113, 327/114, 364/270.2, 364/273.1, 364/273, 364/273.5, 364/707
• US Class Current: 327/113
• CPC Class Codes: G06F 1/08 Clock generators with changeable or programmable clock frequency
• CPC Class Codes: G06F 1/3203 Power management, i.e. event-based initiation of a power-saving mode
• CPC Class Codes: G06F 1/324 by lowering clock frequency
• CPC Class Codes: G06F 1/3287 by switching off individual functional units in the computer system
• CPC Class Codes: Y02D 10/00 Energy efficient computing, e.g. low power processors, power management or thermal management

Abstract

A logic LSI has a plurality of modules such as a CPU contained in one chip. Frequency changing conditions, signals for designating modules whose frequencies are changed for each frequency changing condition, and signals for designating frequencies to be changed are stored in a storage device of a frequency controller, software-wise. The sequentially-input status of the logic LSI is compared with the stored frequency changing conditions and, when the former conforms to the latter, a signal for changing the corresponding frequency is applied to each of the plurality of modules. Each of the modules generates a plurality of internal clocks in synchronization with the basic clock and selects one out of the internal clocks according to the frequency changing signal.

Claims

1. A logic LSI having a plurality of modules including a CPU contained in one chip, comprising:

a basic-clock generator for supplying a basic clock to the modules;

a frequency controller including storage means for storing frequency changing conditions including signals for designating modules whose frequencies are to be changed for each frequency changing condition, and signals for designating predetermined frequencies, for comparing sequentially-input status conditions of the logic LSI with the frequency changing conditions stored in the storage means and, when one of the status conditions conforms with one of the frequency changing conditions, for supplying the modules with a predetermined one of the signals for designating a module for a change of frequency and a corresponding signal for designating one of the predetermined frequencies to which the designated module is to be changed; and

wherein

each of the plurality of modules includes an internal clock generator for generating a plurality of internal clocks in synchronization with the basic clock, means for selectively receiving said predetermined one of the signals for designating a module for a change of frequency when one of the modules is the designated module and further for receiving the corresponding signal for designating one of the predetermined frequencies, and means for selecting one of the internal clocks according to the received corresponding frequency designating signal.

2. A logic LSI according to claim 1, further comprising:

a bus cycle monitor providing a first output signal; and

a timer providing a second output signal, wherein said frequency controller has means for receiving a third output signal provided by an internal operation of the LSI monitor and said first and second output signals as said sequentially input status conditions.

3. A logic LSI according to claim 2, wherein said storage means is a content addressable memory and said receiving means is an encoder having an output that is received by said content addressable memory for comparing said encoder output with the frequency changing conditions stored in the content addressable memory.

4. A logic LSI according to claim 3, wherein said content addressable memory includes a decoder for writing and storing data of said frequency changing conditions into a content addressable array, and further including a data array for storing data of said signals for designating modules whose frequencies are to be changed for each frequency changing condition, and data for said signals for designating predetermined frequencies.

5. A logic LSI according to claim 3, wherein said frequency controller includes a clock controller for storing current operating conditions of the modules and for providing a clock control output that is received by said encoder.

6. A logic LSI according to claim 5, wherein said clock control output is compared with the first, second and third output signals and each time there is a match resulting from the comparison, said signal for designating predetermined frequencies designates an increase by an incremental level to provide a gradual increase in operation speed of a selected module.

7. A logic LSI according to claim 1, wherein said logic LSI is a single-chip microcomputer or an ASIC containing a CPU core.

8. A logic LSI according to claim 5, wherein each said module includes a module designating signal decoder that receives the module designating data signal provided by said frequency controller, a temporary latch that receives said frequency designating data signal, a latch connected to said temporary latch for receiving data from said temporary latch in response to a control signal output from a clock selector which receives a module internal signal representing the internal operating state of the module and also provides an output control signal that is used to select one of a plurality of internal clocks to provide an internal clock output for said selected module.

9. A logic LSI according to claim 8, wherein each said internal clock generator generates said internal clocks at the frequency received from the basic clock generator multiplied or divided by n while controlling phases of said internal clocks.

10. A logic LSI according to claim 9, wherein said module designating signal decoder monitors the module designating signal output from frequency controller and when the selected module is designated by the module designating signal fetches the frequency designating data signal into the temporary latch.

11. A logic LSI according to claim 2, wherein said bus cycle monitor includes comparators, a monitored result output signal generator, an address register, a data register, and a condition register, wherein a first one of the comparators has inputs connected with an internal address bus and the address register, whereas a second one of the comparators has inputs connected with an internal data bus and the data register whereby results of the comparisons performed in said first and second comparators are fed into the monitored result output signal generator, and wherein a condition of making an output of said monitored result output signal generator stored in the condition register is fed into the monitored result output signal generator and the output of the monitored result output signal generator is fed into the frequency controller as the output of the bus cycle monitor.